inst241_sec2

INST 241 (Temperature and Flow Measurement), section 2

Lab

Temperature measurement loop: Questions 91 and 92, completed objectives due by the end of day 4Bulleted questions following lab objectives to be reviewed orally during lab time on day 4

Feedback questions

Questions 81 through 90, due at the end of day 4

Exam

Day 5 – only a simple calculator may be used!Question 93 previews the mastery exam circuit-building activity

Recommended daily schedule

Day 1

Theory session topic: Thermocouples (continued)

Questions 1 through 20; answer questions 1-10 in preparation for discussion (remainder for practice)

Day 2

Theory session topic: Thermocouple and RTD applications


Day 3

Theory session topic: Non-contact pyrometers, temperature switches, calibration standards, andaccessories


Day 4

Theory session topic: Review for exam


Build and test mastery exam circuit (Question 93)

Feedback questions (81 through 90) due at the end of the day

Day 5

Exam

Mastery exam includes the circuit-building activity shown in question 93

Objectives for both “mastery” and “proportional” exams listed in the syllabus (beginning on the next page)

1

INST 241 (Temperature and Flow Measurement)

Credits/hours: 6 credits = 108 clock hours

Prerequisite or corequisite: INST 240 (Pressure and Level Measurement)

Course description: In this course you will learn how to precisely measure both temperature and fluidflow in a variety of applications, as well as accurately calibrate and efficiently troubleshoot temperature andflow measurement systems.

Program outcomes addressed:

(1) Communication; Communicates and expresses thoughts across a variety of mediums (verbal, written,visually) to effectively persuade, inform, and clarify ideas with colleagues.

(2) Time management; Arrives on time and prepared to work; budgets time and meets deadlines whenperforming technical tasks and projects.

(3) Safety; Complies with national, state, and local safety regulations when repairing, calibrating, andinstalling instruments.

(4) Diagnose and repair existing instruments; Assesses, diagnoses, and repairs faulty instruments inmeasurement and control systems using logical procedures and appropriate test equipment.

(5) Install and configure new instruments; Builds, configures and installs new instrument systemsaccording to plans, applying industry construction standards, and ensuring correct system operationwhen complete.

(7) Calibrate instruments; Assesses instrument accuracy and corrects inaccuracies using appropriatecalibration procedures and test equipment.

(8) Document instrument systems; Interprets and creates technical documents (electronic schematics,loop diagrams, and P&IDs) according to industry (EIA, ISA) standards.

(9) Self-directed learning; Selects and researches relevant information sources to learn newinstrumentation principles, technologies, and techniques.

Instructor contact information:

Tony Kuphaldt

Desmond P. McArdle Center

Bellingham Technical College

3028 Lindbergh Avenue

Bellingham, WA 98225-1599

(360)-752-8477 [office phone]

(360)-752-7277 [fax]

[email protected]

Required materials:

• Socratic worksheets: INST241 sec1.pdf, INST241 sec2.pdf, INST241 sec3.pdf, INST241 sec4.pdf

→ Download at: http://openbookproject.net/books/socratic/sinst

• Lessons in Industrial Instrumentation, By Tony R. Kuphaldt. Useful for all quarters of instruction.

→ Download at: http://openbookproject.net/books/socratic/sinst/book/liii.pdf

• Spiral-bound notebook for reading annotation, homework documentation, and note-taking. A separatenotebook for each course is recommended.

• Instrumentation reference CD-ROM (free, from instructor). This disk contains many tutorials anddatasheets in PDF format to supplement your textbook(s).

• Tool kit (see detailed list)

• Simple scientific calculator (non-programmable, non-graphing, no unit conversions, no numerationsystem conversions), TI-30Xa or TI-30XIIS recommended

2

Supplemental materials: (recommended, not required)• “BTCInstrumentation” channel on YouTube (http://www.youtube.com/BTCInstrumentation), hosts

a variety of short video tutorials and demonstrations on instrumentation.• Instrumentation, by Franklyn W. Kirk, published by American Technical Publishers. ISBN-10:

0826934234 ; ISBN-13: 978-0826934239. This text is light on detail and math, but does a good jobintroducing all the major principles and technologies in simple language. Excellent photographs andillustrations, too. Useful for all three quarters of instruction.

• Instrument Engineer’s Handbook, Volume 1: Process Measurement and Analysis, edited by Bela Liptak,published by CRC Press. 4th edition ISBN-10: 0849310830 ; ISBN-13: 978-0849310836.

• Purdy’s Instrument Handbook, by Ralph Dewey. ISBN-10: 1-880215-26-8. A pocket-sized field referenceon basic measurement and control.

• Cad Standard (CadStd) or similar AutoCAD-like drafting software (useful for sketching loop andwiring diagrams). Cad Standard is a simplified clone of AutoCAD, and is freely available at:http://www.cadstd.com

• Any good introductory physics textbook (Applied Physics by Tippens, or Conceptual Physics by Hewitt)• CRC Handbook of Chemistry and Physics

Student performance objectives:Assessment legend: [P] = Preparation, [L] = Lab, [F] = Feedback questions, [X] = Exam

• Mastery (must eventually be demonstrated without error)• [L] Calibration of thermocouple temperature transmitter to specified range and accuracy• [L] Calibration of RTD temperature transmitter to specified range and accuracy• [L] Calibration of liquid or gas flow transmitter to specified range and accuracy• [L] Create accurate as-built loop diagrams• [L] Create accurate P&IDs• [L] Troubleshoot a problem within an electronic (4-20 mA loop) temperature measurement system, given

a specified time to logically identify the location and nature of the problem• [L] Work safely and constructively within a team• [X1] Build a circuit to sense temperature using a thermocouple or RTD temperature transmitter• [X1] Convert between different units of temperature – only a simple calculator may be used!• [X1] Identify thermocouple types, color codes, metals, and temperature ranges• [X1] Calculate temperature or resistance of an RTD given the other variable• [X1] Calculate instrument calibration points given ranges• [X1] INST251 Review: identify proper controller action (direct or reverse) for a process• [X1] INST261 Review: sketch an equivalent ladder logic diagram for a given truth table• [X2] Build a circuit with a “smart” transmitter and use a HART communicator to re-range it• [X2] Identify operating principle for different types of flow-sensing elements• [X2] Identify characterization (linear vs. nonlinear) of different flow-sensing elements• [X2] Calculate new ∆P ranges for altered orifice flow ranges• [X2] Identify suitability of basic flow-measuring instruments to different processes• [X2] Identify proper installation configurations for different process fluids and flow instruments• [X2] Calculate turbine flowmeter calibration points given ranges (k factor)• [X2] INST251 Review: calculate or graph response of proportional-only controller to input changes over

time• [X2] INST262 Review: identify the purpose of a distributive control system (DCS)

• Proportional (graded on a percentage scale according to quality/quantity of fulfillment)• [P] Identify and use appropriate sources of information for independent learning• [L] Explain how to diagnose a hypothetical problem in a temperature measurement system• [L] Explain how to diagnose a hypothetical problem in a flow measurement system• [L] Explain or demonstrate a principle relevant to a temperature measurement system• [L] Explain or demonstrate a principle relevant to a flow measurement system• [L] Perform a basic math calculation relevant to a temperature measurmement system

3

• [L] Perform a basic math calculation relevant to a flow measurmement system• [L] Explain or demonstrate safety procedure or tool usage• [F] Qualitatively analyze a heat exchanger system• [F] Convert between different units of temperature• [F] Explain how a filled-bulb primary sensing element works• [F] Interpret the millivoltage output of a thermocouple• [F] Calorimetry calculation• [F] Solving for variables in an equation (kinetic energy equation)• [F] Calculating V, I, P in a series-parallel DC network (schematic)• [F] Calculate V and I in an AC transformer circuit (schematic)• [F] Qualitative fault analysis in a DC circuit (pictorial)• [F] Troubleshooting: OptoTRIAC solenoid control circuit• [F] Troubleshoot thermocouple problems• [F] Analyze an RTD bridge circuit• [F] Analyze a thermistor circuit• [F] Apply the physics of phase changes to a heat exchanger system• [F] Explain how Stefan-Boltzmann Law of radiated energy relates to practical temp measurement• [F] Trigonometric calculation (Law of Sines)• [F] Qualitative analysis of a practical equation (electrical resonant frequency)• [F] Calculating V in a DC network using KVL (schematic)• [F] Qualitative fault analysis in a DC circuit (pictorial)• [F] Troubleshooting: Automotive fuel gauge circuit (using current mirror)• [F] Describe and explain exchange of energy as fluid moves through an orifice• [F] Describe procedure for working with an insertion-type flow meter• [F] Compare and contrast weirs/flumes with orifice plates• [F] Determine a calibration table for all instruments in a flow-measurement loop• [F] Analyze pressure losses along pipes for linearity with flow rate• [F] Binary-to-hexadecimal conversion• [F] Oscilloscope waveform interpretation• [F] Calculate required time in an RC charge/discharge circuit (schematic)• [F] Loop wiring: two transmitters, two 4-20 mA input channels on MicroLogix PLC (pictorial)• [F] Troubleshooting: Digital logic gate security alarm circuit• [F] Calculate new ∆P range for an altered orifice flow range• [F] Explain vortex flow meter operation• [F] Explain magnetic flow meter operation• [F] Identify need for mass flow measurement• [F] Identify which types of flow-sensing elements require characterization (linear vs. nonlinear)• [F] Solving for variables in an equation (valve flow equation)• [F] Qualitative analysis of a practical equation (proportional controller equation)• [F] Qualitative fault analysis in a DC circuit (schematic)• [F] Three-phase motor connections (pictorial)• [F] Troubleshooting: Three-phase motor control circuit• [X1] Calculate electronic circuit parameters related to temperature measurement, both thermocouple

and RTD• [X1] Select an appropriate temperature-measuring technology for a specific application• [X1] Use the Ideal Gas Law to calculate pressure, volume, molecular gas quantity, or temperature given

the other variables.• [X1] Complete a simple circuit design for temperature measurement• [X2] Complex flow rate calculation(s)• [X2] Calculation(s) involving square root extraction• [X2] Flow stream conditioning requirements and techniques• [X2] Volumetric versus mass flow measurement• [X2] Flow measurement problem diagnosis

4

file INST241syllabus

5

Sequence of second-year Instrumentation courses

(or equivalent)

INST 200 -- 1 wk INST 205 -- 1 wk

GRADUATION !

Job Prep IIntro. to InstrumentationINST 206 -- 1 wk

Job Prep II

1st quarter 2nd quarter 3rd quarter

Pressure and LevelMeasurement

Measurement

MeasurementAnalytical

Temperature and Flow

INST 240 -- 4 wks

INST 241 -- 4 wks

Fal

l qu

arte

r

INST 242 -- 3 wks

Final ControlElements

Process Optimizationand Control Strategies

PID Controllersand Tuning

INST 250 -- 4 wks

INST 251 -- 4 wks

Win

ter

qu

arte

r

INST 252 -- 3 wks

Data AcquisitionSystems

Programmable LogicControllers

DCS and Fieldbus

INST 261 -- 4 wks

INST 262 -- 4 wks

Sp

rin

g q

uar

ter

INST 260 -- 3 wks

continuing students

(after completing all three quarters)

Core Electronics -- 1 year

file sequence

6

General student expectations

(Punctuality) You are expected to arrive at school on time (by 8:00 AM) every day. One late arrivalis permitted during the timespan of each sequential course (e.g. INST240, INST241, etc.) with no gradededuction. The grade deduction rate for late arrivals is 1% per incident.

(Attendance) You are expected to attend all day, every day. Each student has 12 “sick hours” per quarterapplicable to absences not verifiably employment-related, school-related, or weather-related. The gradededuction rate is 1% per hour of absence in any course. Each student must confer with the instructor toapply “sick hours” to any missed time – this is not done automatically for the student. Students may donateunused “sick hours” to whomever they specifically choose. You should contact your instructor and teammembers immediately if you know you will be late or absent. Absence on an exam day will result in a failinggrade for that exam, unless due to a documented emergency. Exams may be taken in advance for full credit.

(Participation) You are expected to participate fully in all aspects of the learning process includingindependent study, lab project completion, and classroom activities. It is solely your responsibility to catchup on all information missed due to absence. Furthermore, you shall not interfere with the participation ofothers in the learning process.

(Teamwork) You will work in instructor-assigned teams to complete lab assignments. Team membershipis determined by accumulated attendance and punctuality scores: students with similar participatory trendsare teamed together. Any student compromising team performance through frequent absence, habitualtardiness, or other disruptive behavior(s) will be expelled from their team and required to complete alllabwork independently for the remainder of the quarter.

(Preparation for theory sessions) You must dedicate at least 2 hours each day for reading assignmentsand homework questions to prepare yourself for theory sessions, where you will actively contribute your newknowledge. Graded quizzes and/or work inspections during each theory session will gauge your independentlearning. If absent, you may receive credit by having your preparatory work thoroughly reviewed prior tothe absence, or passing a comparable quiz after the absence.

(Feedback questions) You must complete and submit feedback questions for each section by the specifieddeadline. These are graded for accuracy and recorded as a “feedback” score. Plagiarism (presenting anyoneelse’s work as you own) in your answers will result in a zero score. It is okay to help one another learn thematerial, and to learn from outside sources, but your explanations must be phrased in your own words andwith your own work shown.

(Disciplinary action and instructor authority) The Student Code of Conduct (WashingtonAdministrative Codes WAC 495B-120) explicitly authorizes disciplinary action against the following typesof misconduct: academic dishonesty (e.g. cheating, plagiarism), dangerous or lewd behavior, harassment,intoxication, destruction of property, and/or disruption of the learning environment. Furthermore, the Codestates “Instructors have the authority to take whatever summary actions may be necessary to maintain orderand proper conduct in the classroom and to maintain the effective cooperation of the class in fulfilling theobjectives of the course.” Distractive or disruptive behavior such as (but not limited to) unauthorizedtelephone or computer use, disrespectful comments, sleeping, and conversation that either impede yourparticipation or the participation of others may result in temporary dismissal from class with attendancehours deducted.

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General grading and evaluation standards

Assessment criteria

• Mastery (all must be mastered – constitutes first 50% of course grade)• Mastery section of each lab exercise (unlimited attempts)• Mastery section of each exam including the hands-on circuit building or troubleshooting activity (up to

two attempts per sitting; up to three sittings); or mastery capstone assessment (unlimited attempts)

• Proportional (grades based on quality of fulfillment, counts toward last 50% of course grade)• Labwork, consisting of questions answered in an oral and demonstrative format (10% of grade)• Proportional section of all exams (20% of grade)• Feedback questions for all sections (20% of grade)• Daily quizzes demonstrating preparation for theory sessions (-1% per failed quiz)• Daily punctuality (-1% per incident of tardiness)• Attendance (-1% per hour past allotted “sick time”)• Destroyed items (-10% per incident) or purchase and replacement of the damaged item – This regards

avoidable incidents due to personal carelessness. When in doubt, ask the instructor how to properlyuse a tool or piece of equipment!

• Repaired instruments (+5% per item) – Instrument identified in need of repair by the instructor

Negative weighting represent objectives where 100% passing is a basic expectation (passing every quiz,punctuality every day, no accidents, etc.). Perfectly meeting these expectations does not count toward yourgrade, but failing to meet these basic expectations will result in grade loss.

Grading scaleAll grades are criterion-referenced (i.e. no grading on a “curve”)

• 100% ≥ A ≥ 95% 95% > A- ≥ 90%• 90% > B+ ≥ 86% 86% > B ≥ 83% 83% > B- ≥ 80%• 80% > C+ ≥ 76% 76% > C ≥ 73% 73% > C- ≥ 70% (minimum passing course grade)• 70% > D+ ≥ 66% 66% > D ≥ 63% 63% > D- ≥ 60% 60% > F

The proportional section of an exam may be taken only after taking the mastery section. Failing themastery exam will result in a 50% deduction from the proportional exam score, and you get a maximum oftwo re-takes to pass the mastery which must occur within three school days of the first attempt. Failure topass the mastery within three sittings will result in a failing grade for the course. Absence on a scheduledexam day will result in a 0% score for the proportional exam unless you provide documented evidence of anunavoidable emergency. You may receive half-credit on missed proportional exam questions after grading byexplaining your original mistake(s) and providing completely corrected responses on the first attempt.

If any other “mastery” objectives are not completed by their specified deadlines, your overall gradefor the course will be capped at 70% (C- grade), and you will have one more course day to complete theunfinished objectives. Failure to complete those mastery objectives by the end of that extra day (except inthe case of documented, unavoidable emergencies) will result in a failing grade (F) for the course.

Answers to “feedback questions” are due at the end of each course section. Full credit is given foreach question correctly and thoroughly answered, half credit for each question either not fully answeredor containing minor errors, and zero credit for major conceptual errors. Late submissions will receive zerocredit, unless due to a documented emergency.

“Lab questions” are assessed in a group format where students take turns answering questions from thelist at the instructor’s prompting. Grading follows the same rubric as for feedback questions: full creditfor thorough, correct answers; half credit for partially correct answers, and zero credit for major conceptualerrors. If you are absent during this assessment, you must submit written answers to all of the lab questions,which will be graded by the instructor.

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General tool and supply list

Wrenches• Combination (box- and open-end) wrench set, 1/4” to 3/4” – the most important wrench sizes are 7/16”,

1/2”, 9/16”, and 5/8”; get these immediately!• Miniature combination wrench set, 3/32” to 1/4”• Adjustable wrench, 6” handle• Hex wrench (“Allen” wrench) set, fractional – 1/16” to 3/8”

Note: when turning a bolt, nut, or tube fitting with a hexagonal body, the preferred ranking of handtools to use (from first to last) is box-end wrench or socket, open-end wrench, and finally adjustable wrench.Pliers should never be used to turn the head of a fitting or fastener unless it is absolutely unavoidable!

Pliers• Needle-nose pliers• Slip-joint pliers• Diagonal wire cutters

Screwdrivers• Slotted, 1/8” and 1/4” shaft• Phillips, #1 and #2• Jeweler’s screwdriver set

Measurement tools• Tape measure. 12 feet minimum• Vernier calipers, plastic okay

Electrical• Multimeter, Fluke model 87-IV or better• Wire strippers/terminal crimpers with a range including 10 AWG to 18 AWG wire• Soldering iron, 10 to 25 watt• Rosin-core solder• Package of compression-style fork terminals (e.g. Thomas & Betts “Sta-Kon” part number 14RB-10F,

14 to 18 AWG wire size, #10 stud size)

Safety• Safety glasses or goggles (available at BTC bookstore)• Earplugs (available at BTC bookstore)

Miscellaneous• Teflon pipe tape• Utility knife

You are recommended to engrave your name or place some other form of identifying mark on your tools,as you will be doing a lot of your work in teams, and it is easy to get tools mixed up. Also, lost tools getreturned to their owners much faster when they are marked!

An inexpensive source of high-quality tools is your local pawn shop. Look for name-brand tools withunlimited lifetime guarantees (e.g. Sears “Craftsman” brand, Snap-On, etc.).

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Methods of instruction

This course develops self-instructional and diagnostic skills by placing students in situations where theyare required to research and think independently. In all portions of the curriculum, the goal is to avoid apassive learning environment, favoring instead active engagement of the learner through reading, reflection,problem-solving, and experimental activities. The curriculum may be roughly divided into two portions:theory and practical.

TheoryIn the theory portion of each course, students independently research subjects prior to entering the

classroom for discussion. At the start of the classroom session, the instructor will check each student’spreparation using one of several methods (direct inspection of work, a pop quiz, targeted questions, etc.).Students then spend some class time working in small groups coordinating their presentations. The rest ofthe class time is spent interacting Socratically with the instructor in a large-group dialogue. The instructorcalls students (or student groups) to present what they found in their research, questions that arose duringtheir study, their solutions to problems, and any problem-solving techniques applied. The instructor’s roleis to help students take the information gleaned from their research and convert this into understanding.

LabIn the lab portion of each course, students work in teams to install, configure, document, calibrate, and

troubleshoot working instrument loop systems. Each lab exercise focuses on a different type of instrument,with a eight-day period typically allotted for completion. An ordinary lab session might look like this:

(1) Start of practical (lab) session: announcements and planning(a) Instructor makes general announcements to all students(b) Instructor works with team to plan that day’s goals, making sure each team member has a clear

idea of what they should accomplish(2) Teams work on lab unit completion according to recommended schedule:

(First day) Select and bench-test instrument(s)(One day) Connect instrument(s) into a complete loop(One day) Each team member drafts their own loop documentation, inspection done as a team (withinstructor)(One or two days) Each team member calibrates/configures the instrument(s)(Remaining days, up to last) Each team member troubleshoots the instrument loop(Last day) All teams answer lab questions, one team at a time, with the instructor

(3) End of practical (lab) session: debriefing where each team reports on their work to the whole class

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Distance delivery methods

Sometimes the demands of life prevent students from attending college 6 hours per day. In such cases,there exist alternatives to the normal 8:00 AM to 3:00 PM class/lab schedule, allowing students to completecoursework in non-traditional ways, at a “distance” from the college campus proper.

For such “distance” students, the same worksheets, lab activities, exams, and academic standards stillapply. Instead of working in small groups and in teams to complete theory and lab sections, though, studentsparticipating in an alternative fashion must do all the work themselves. Participation via teleconferencing,video- or audio-recorded small-group sessions, and such is encouraged and supported.

There is no recording of hours attended or tardiness for students participating in this manner. The paceof the course is likewise determined by the “distance” student. Experience has shown that it is a benefit for“distance” students to maintain the same pace as their on-campus classmates whenever possible.

In lieu of small-group activities and class discussions, comprehension of the theory portion of each coursewill be ensured by completing and submitting detailed answers for all worksheet questions, not just passingdaily quizzes as is the standard for conventional students. The instructor will discuss any incomplete and/orincorrect worksheet answers with the student, and ask that those questions be re-answered by the studentto correct any misunderstandings before moving on.

Labwork is perhaps the most difficult portion of the curriculum for a “distance” student to complete,since the equipment used in Instrumentation is typically too large and expensive to leave the school labfacility. “Distance” students must find a way to complete the required lab activities, either by arrangingtime in the school lab facility and/or completing activities on equivalent equipment outside of school (e.g.at their place of employment, if applicable). Labwork completed outside of school must be validated by asupervisor and/or documented via photograph or videorecording.

Conventional students may opt to switch to “distance” mode at any time. This has proven to be abenefit to students whose lives are disrupted by catastrophic events. Likewise, “distance” students mayswitch back to conventional mode if and when their schedules permit. Although the existence of alternativemodes of student participation is a great benefit for students with challenging schedules, it requires a greaterinvestment of time and a greater level of self-discipline than the traditional mode where the student attendsschool for 6 hours every day. No student should consider the “distance” mode of learning a way to havemore free time to themselves, because they will actually spend more time engaged in the coursework thanif they attend school on a regular schedule. It exists merely for the sake of those who cannot attend duringregular school hours, as an alternative to course withdrawal.

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General advice for successful learning

Reserve a time and a place for study• Schedule a block of time every day for study and make it a priority!• Create or join a study group, and help each other commit to regular study time.• Keep the environment of your study place ideal: whatever music (or no music) helps you concentrate,

whatever time allows for the least number of distractions, etc.• Plan to arrive at school at least a half-hour early and use the time to study as opposed to studying late

at night. This also helps guard against tardiness in the event of unexpected delays, and ensures you abetter parking space!

Who to study with• Classmates with similar schedules.• Classmates who are serious about their education.• Note that the intelligence of your study partners is not a significant criterion!

How to make time for study• Rid yourself of unnecessary, time-wasting gadgets: televisions, video games, mobile phones, etc. I am

not kidding!• Avoid recreational use of the internet.• Bring a meal to school every day and use your one-hour lunch break for study instead of eating out.• Carefully plan your lab sessions with your teammates to reserve a portion of each day’s lab time for

study.• Cut off all unhealthy personal relationships.

Make efficient use of the time you have• Do not procrastinate, waiting until the last minute to do something.• Don’t let small chunks of time at home or at school go to waste. Work a little bit on assignments during

these times.• Identify menial chores you can do simultaneously (e.g. house cleaning and laundry), and plan your

chore time accordingly to free up more time at home.

Take responsibility for your learning and your life• Obtain all the required books, and any supplementary study materials available to you. If the books

cost too much, look on the internet for used texts (www.amazon.com, www.half.com, etc.) and use themoney from the sale of your television and video games to buy them!

• Make an honest attempt to solve problems before asking someone else to help you. Being able toproblem-solve is a skill that will improve only if you continue to do work at it.

• If you detect trouble understanding a basic concept, seek clarification on it immediately. Never ignorean area of confusion, believing you will pick up on it later. Later may be too late!

• Do not wait for others to do things for you. No one is going to make extra effort purely on your behalf.• Seek help for any addictions. Addictions won’t just destroy your chance at an education – they can

destroy your whole life!

. . . And the number one tip for success . . .• Realize that there are no shortcuts to learning. Every time you seek a shortcut, you are actually cheating

yourself out of a learning opportunity!!

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Creative Commons License

This worksheet is licensed under the Creative Commons Attribution License, version 1.0. To viewa copy of this license, visit http://creativecommons.org/licenses/by/1.0/ or send a letter to CreativeCommons, 559 Nathan Abbott Way, Stanford, California 94305, USA. The terms and conditions of thislicense allow for free copying, distribution, and/or modification of all licensed works by the general public.

Simple explanation of Attribution License:

The licensor (Tony Kuphaldt) permits others to copy, distribute, display, and otherwise use thiswork. In return, licensees must give the original author(s) credit. For the full license text, please visithttp://creativecommons.org/licenses/by/1.0/ on the internet.

More detailed explanation of Attribution License:

Under the terms and conditions of the Creative Commons Attribution License, you may make freelyuse, make copies, and even modify these worksheets (and the individual “source” files comprising them)without having to ask me (the author and licensor) for permission. The one thing you must do is properlycredit my original authorship. Basically, this protects my efforts against plagiarism without hindering theend-user as would normally be the case under full copyright protection. This gives educators a great dealof freedom in how they might adapt my learning materials to their unique needs, removing all financial andlegal barriers which would normally hinder if not prevent creative use.

Nothing in the License prohibits the sale of original or adapted materials by others. You are free tocopy what I have created, modify them if you please (or not), and then sell them at any price. Once again,the only catch is that you must give proper credit to myself as the original author and licensor. Given thatthese worksheets will be continually made available on the internet for free download, though, few peoplewill pay for what you are selling unless you have somehow added value.

Nothing in the License prohibits the application of a more restrictive license (or no license at all) toderivative works. This means you can add your own content to that which I have made, and then exercisefull copyright restriction over the new (derivative) work, choosing not to release your additions under thesame free and open terms. An example of where you might wish to do this is if you are a teacher who desiresto add a detailed “answer key” for your own benefit but not to make this answer key available to anyoneelse (e.g. students).

Note: the text on this page is not a license. It is simply a handy reference for understanding the LegalCode (the full license) - it is a human-readable expression of some of its key terms. Think of it as theuser-friendly interface to the Legal Code beneath. This simple explanation itself has no legal value, and itscontents do not appear in the actual license.

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Metric prefixes and conversion constants

• Metric prefixes

• Yotta = 1024 Symbol: Y

• Zeta = 1021 Symbol: Z

• Exa = 1018 Symbol: E

• Peta = 1015 Symbol: P

• Tera = 1012 Symbol: T

• Giga = 109 Symbol: G

• Mega = 106 Symbol: M

• Kilo = 103 Symbol: k

• Hecto = 102 Symbol: h

• Deca = 101 Symbol: da

• Deci = 10−1 Symbol: d

• Centi = 10−2 Symbol: c

• Milli = 10−3 Symbol: m

• Micro = 10−6 Symbol: µ

• Nano = 10−9 Symbol: n

• Pico = 10−12 Symbol: p

• Femto = 10−15 Symbol: f

• Atto = 10−18 Symbol: a

• Zepto = 10−21 Symbol: z

• Yocto = 10−24 Symbol: y

1001031061091012 10-3 10-6 10-9 10-12(none)kilomegagigatera milli micro nano pico

kMGT m µ n p

10-210-1101102

deci centidecahectoh da d c

METRIC PREFIX SCALE

• Conversion formulae for temperature

• oF = (oC)(9/5) + 32

• oC = (oF - 32)(5/9)

• oR = oF + 459.67

• K = oC + 273.15

Conversion equivalencies for distance

1 inch (in) = 2.540000 centimeter (cm)

1 foot (ft) = 12 inches (in)

1 yard (yd) = 3 feet (ft)

1 mile (mi) = 5280 feet (ft)

14

Conversion equivalencies for volume

1 gallon (gal) = 231.0 cubic inches (in3) = 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl. oz.)= 3.7854 liters (l)

1 milliliter (ml) = 1 cubic centimeter (cm3)

Conversion equivalencies for velocity

1 mile per hour (mi/h) = 88 feet per minute (ft/m) = 1.46667 feet per second (ft/s) = 1.60934kilometer per hour (km/h) = 0.44704 meter per second (m/s) = 0.868976 knot (knot – international)

Conversion equivalencies for mass

1 pound (lbm) = 0.45359 kilogram (kg) = 0.031081 slugs

Conversion equivalencies for force

1 pound-force (lbf) = 4.44822 newton (N)

Conversion equivalencies for area

1 acre = 43560 square feet (ft2) = 4840 square yards (yd2) = 4046.86 square meters (m2)

Conversion equivalencies for common pressure units (either all gauge or all absolute)

1 pound per square inch (PSI) = 2.03602 inches of mercury (in. Hg) = 27.6799 inches of water (in.W.C.) = 6.894757 kilo-pascals (kPa) = 0.06894757 bar

1 bar = 100 kilo-pascals (kPa)

Conversion equivalencies for absolute pressure units (only)

1 atmosphere (Atm) = 14.7 pounds per square inch absolute (PSIA) = 101.325 kilo-pascals absolute(kPaA) = 1.01325 bar (bar) = 760 millimeters of mercury absolute (mmHgA) = 760 torr (torr)

Conversion equivalencies for energy or work

1 british thermal unit (Btu – “International Table”) = 251.996 calories (cal – “International Table”)= 1055.06 joules (J) = 1055.06 watt-seconds (W-s) = 0.293071 watt-hour (W-hr) = 1.05506 x 1010

ergs (erg) = 778.169 foot-pound-force (ft-lbf)

Conversion equivalencies for power

1 horsepower (hp – 550 ft-lbf/s) = 745.7 watts (W) = 2544.43 british thermal units per hour(Btu/hr) = 0.0760181 boiler horsepower (hp – boiler)

Acceleration of gravity (free fall), Earth standard

9.806650 meters per second per second (m/s2) = 32.1740 feet per second per second (ft/s2)

15

Physical constants

Speed of light in a vacuum (c) = 2.9979 × 108 meters per second (m/s) = 186,281 miles per second(mi/s)

Avogadro’s number (NA) = 6.022 × 1023 per mole (mol−1)

Electronic charge (e) = 1.602 × 10−19 Coulomb (C)

Boltzmann’s constant (k) = 1.38 × 10−23 Joules per Kelvin (J/K)

Stefan-Boltzmann constant (σ) = 5.67 × 10−8 Watts per square meter-Kelvin4 (W/m2·K4)

Molar gas constant (R) = 8.314 Joules per mole-Kelvin (J/mol-K)

Properties of Water

Freezing point at sea level = 32oF = 0oC

Boiling point at sea level = 212oF = 100oC

Density of water at 4oC = 1000 kg/m3 = 1 g/cm3 = 1 kg/liter = 62.428 lb/ft3 = 1.94 slugs/ft3

Specific heat of water at 14oC = 1.00002 calories/g·oC = 1 BTU/lb·oF = 4.1869 Joules/g·oC

Specific heat of ice ≈ 0.5 calories/g·oC

Specific heat of steam ≈ 0.48 calories/g·oC

Absolute viscosity of water at 20oC = 1.0019 centipoise (cp) = 0.0010019 Pascal-seconds (Pa·s)

Surface tension of water (in contact with air) at 18oC = 73.05 dynes/cm

pH of pure water at 25o C = 7.0 (pH scale = 0 to 14)

Properties of Dry Air at sea level

Density of dry air at 20oC and 760 torr = 1.204 mg/cm3 = 1.204 kg/m3 = 0.075 lb/ft3 = 0.00235slugs/ft3

Absolute viscosity of dry air at 20oC and 760 torr = 0.018 centipoise (cp) = 1.8 × 10−5 Pascal-seconds (Pa·s)

file conversion constants

16

Question 0

How to read actively:

• Make notes in a notebook while reading – if you’re not “reading with a pencil,” you’re not activelyreading! “Shorthand” notation, diagrams, and other notes jotted in a notebook are more effective atprompting active reading than underlining, highlighting, or otherwise marking up the original text.

• Mentally summarize each new concept or application you encounter in your own words before movingon to the next. If you cannot do this, you know you need to re-read the relevant sections until you can!

• Try to link new concepts to previously-learned concepts, and imagine how new concepts might apply toapplications not mentioned in the text. Make notes on these points so you may raise them as questionsduring class time.

• Note page numbers where important concepts, equations, images, tables, and problem-solving techniquesare introduced This will help you locate these important references during class time when you willcontribute in the dicsussion (“On page 572 it shows . . .”).

• Note page numbers of any sections in the reading that confound you, so you may call attention to it atthe start of class time to get help from classmates and/or the instructor.

• If the text demonstrates a mathematical calculation, such as how to apply a new equation to solving aproblem, pick up your calculator and work through the example as you read! Applications of math arean ideal opportunity to actively read a technical book, actually engaging in the material rather thanpassively observing what it says.

• Reserve the front pages of your notebook (or keep a separate notebook) for all mathematical formulaeyou come across in your reading. Briefly explain in your own words what each formula does and whatits terms mean.

Problem-solving techniques

• Clearly identify all “given” information, and also what the question is asking you to determine or solve.

• Sketch a diagram or graph to organize all the “given” information and show where the answer will fit.

• Performing “thought experiments” to visualize the effects of different conditions.

• Working “backward” from a hypothetical solution to a new set of given conditions.

• Changing the problem to make it simpler, and then solving the simplified problem (e.g. changingquantitative to qualitative, or visa-versa; substituting different numerical values to make them easierto work with; eliminating confusing details; adding details to eliminate unknowns; considering limitingcases that are easier to grasp).

• Identify any “first principles” of science, electronics, and/or instrumentation (e.g. Conservation laws,Feedback, Zero and Span, Ohm’s Law, etc.) that might apply to the question.

• Specifically identify which portion(s) of the question you find most confusing and need help with. Themore specific you are able to be, the better.

file question0

17

Questions

Question 1

Read and outline the “Reference Junction Compensation” subsection of the “Thermocouples” sectionof the “Continuous Temperature Measurement” chapter in your Lessons In Industrial Instrumentationtextbook. Note the page numbers where important illustrations, photographs, equations, tables, and otherrelevant details are found. Prepare to thoughtfully discuss with your instructor and classmates the conceptsand examples explored in this reading.

file i03990

Question 2

Read and outline the “Law of Intermediate Metals” subsection of the “Thermocouples” section of the“Continuous Temperature Measurement” chapter in your Lessons In Industrial Instrumentation textbook.Note the page numbers where important illustrations, photographs, equations, tables, and other relevantdetails are found. Prepare to thoughtfully discuss with your instructor and classmates the concepts andexamples explored in this reading.

file i03991

Question 3

Read and outline the “Software Compensation” subsection of the “Thermocouples” section of the“Continuous Temperature Measurement” chapter in your Lessons In Industrial Instrumentation textbook.Note the page numbers where important illustrations, photographs, equations, tables, and other relevantdetails are found. Prepare to thoughtfully discuss with your instructor and classmates the concepts andexamples explored in this reading.

file i03992

Question 4

Read and outline the “Extension Wire” subsection of the “Thermocouples” section of the “ContinuousTemperature Measurement” chapter in your Lessons In Industrial Instrumentation textbook. Note the pagenumbers where important illustrations, photographs, equations, tables, and other relevant details are found.Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored inthis reading.

file i03993

Question 5

Read and outline the “Side-Effects of Reference Junction Compensation” subsection of the“Thermocouples” section of the “Continuous Temperature Measurement” chapter in your Lessons InIndustrial Instrumentation textbook. Note the page numbers where important illustrations, photographs,equations, tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructorand classmates the concepts and examples explored in this reading.

file i03994

Question 6

Read and outline the “Burnout Detection” subsection of the “Thermocouples” section of the“Continuous Temperature Measurement” chapter in your Lessons In Industrial Instrumentation textbook.Note the page numbers where important illustrations, photographs, equations, tables, and other relevantdetails are found. Prepare to thoughtfully discuss with your instructor and classmates the concepts andexamples explored in this reading.

file i03995

18

Question 7

The relationship between the amount of voltage produced by a thermocouple’s measurement junction(Emeas), the voltage produced by the reference junction (Eref ), and the voltage received by the measuringinstrument (Emeter) is stated by the following equation:

VoltmeterEmeas

Eref

EmeterThermocouple

Thermocouple wire

Thermocouple wire

Copper wire

Copper wire

Emeter = Emeas − Eref

In a hardware-compensated thermocouple measuring instrument, the reference junction’s voltage iscanceled by the addition of a variable voltage source inside the instrument which we will designate asEcomp. An alternative approach is to connect an external device called an electronic ice-point between thevoltage-measuring instrument and the thermocouple, such that the “ice point” device adds the necessaryvoltage to compensate for the reference junction:

VoltmeterEmeas

Eref

EmeterThermocouple

Thermocouple wire

Thermocouple wire

Copper wire

Copper wire

Compensatingcircuit

Electronic ice-point

Re-write the thermocouple circuit equation to include this “compensating” voltage, and identify boththe magnitude and the polarity this voltage must have in order to successfully cancel Eref .

file i00385

19

Question 8

Thermocouple-based temperature instruments work on the principle of measuring voltage output by athermocouple:

Cu

CuT

+ -TC wire

TC wire

ProcessTemperature instrument

CuCu

Instrument in use

+

-

+

-

If we try to simulate a thermocouple by using a precision potentiometer circuit to send a precise millivoltsignal to a temperature instrument, however, the instrument will not register the way we might expect. Forinstance, thermocouple tables for type J thermocouples tell us that 500 oF corresponds to a voltage signalof 14.110 mV. However, if we were to input this amount of signal voltage to a type J instrument, it wouldprobably not register 500 oF:

Cu

CuT

+ -

Temperature instrument

CuCu

Instrument in calibration

Cu

Cu

Precisionpotentiometer

+

-

+

-

Cu

Cu

Describe what the problem is, and determine the amount of voltage we would have to “dial up” on theprecision potentiometer in order to get the thermocouple instrument to register 500 oF, assuming an ambienttemperature of 72 oF.

file i00386

20

Question 9

Write an equation for each circuit shown, showing how all the voltages in each circuit relate to eachother:

Cu+ -

TC wire

TC wire


Cu

+

-

+

-Einstrument

Ereference

Emeasurement

(primitive)

Equation:

Cu+ -

TC wire

TC wire


Cu

+

-

+

-

Einstrument

Ereference

Emeasurement

Equation:

T

Ecompensation

+ -

21

Cu+ -


Cu

+

-

+

-

Einstrument

Equation:

T

Ecompensation

+ -


Cu

Cu

Cu

CuEpotentiometer

Cu+ -


Cu

+

-

+

-

Einstrument

Equation:

T

Ecompensation

+ -


Cu

CuEpotentiometer

TC wire

TC wire

Emeasurement

Ereference

file i00387

22

Question 10

Determine the correct potentiometer millivoltage setting to generate the following temperatureindications on the following instruments:

Cu+ -


Cu

+

-

+

-T

+ -


Cu

Cu

Cu

Cu

(type K thermocouple)

Temp. = 76o F

Temp. = 65o F

• 0o F ; Potentiometer setting = ???



Cu+ -


Cu

+

-

+

-T

+ -


Cu

Cu

Cu

Cu

(type J thermocouple)

Temp. = 68o F

Temp. = 73o F




23

Cu+ -


Cu

+

-

+

-T

+ -


Cu

Cu

Cu

Cu

(type J thermocouple)

Temp. = 70o F

Temp. = 50o F

• 250o F ; Potentiometer setting = ???• 500o F ; Potentiometer setting = ???• 750o F ; Potentiometer setting = ???

file i00388

Question 11

It is important for a thermocouple-based temperature instrument to have a high input impedance. Whatdoes this mean, and why is it important in a thermocouple circuit?

Modern digital voltmeter designs all exhibit high input impedance – high enough for measuringthermocouple junction voltage, at least. Suppose, though, you were asked to measure the output ofa thermocouple without using any digital instruments. You have plenty of analog voltmeter movementsavailable, but they all have input impedances that are too low for this task.

Describe how you could build your own super-high input impedance voltmeter using readily availablecomponents. Extra points for doing so without using an electronic circuit!

file i00394

24

Question 12

The following diagram is a simplified schematic for a 2-wire, loop-powered, 4-20 mA analog temperaturetransmitter:

−

+

Rsense

Rlimit

(ground)

Voltageregulator

InOut

Gnd

Rfeedback

Rbias

Out

Gnd

+V

Thermocouple

Op-amp

+V

Gnd

Amplifyingand scaling

circuitry

Loop-powered 4-20 mA temperature transmitter

The rest of the circuit, of course, looks something like this:

ThermocoupleLoop-powered

transmitter

2-wire cable

+ −

24 VDC

R

Calculate the amount of current through the emitter of the transistor inside the temperature transmittergiven the following conditions:

• Calibrated temperature range = 50 to 250 degrees C• Thermocouple temperature = 100 degrees C• Loop power supply = 24.0 volts• Loop resistance = 250 ohms• Voltage regulator input current = 3.7 mA (constant)

Also, trace the directions of all currents in the temperature transmitter circuit using both conventionaland electron flow notations.

file i00397

25

Question 13

The HART protocol was an early attempt at establishing a digital communications standard for fieldprocess instruments, designed as an extension of the already-popular 4 to 20 mA DC current signal standard.The basic idea of HART is that serial digital data could be encoded as bursts of high-frequency AC voltagesuperimposed on the DC voltage present in a 4-20 mA loop-powered circuit:

Loop-poweredtransmitter

250 Ω 24 VDC

C

DC power source

HART communicator

(HART-compatible)

4-20 mA DC

Indicator(1-5 VDC)

A microprocessor inside the loop-powered transmitter detects the digital data signals from the HARTcommunicator as pulses of low-voltage AC dropped across the transmitter terminals. The transmitter, inturn, has the ability to send digital data out in the same format, being detected by the communicator asAC voltage pulses across its terminals.

Apply the Superposition Theorem to this circuit, showing the circuit as “seen” by the AC signals sentbetween the transmitter and communicator, and showing the circuit as “seen” by the DC signals sent betweenthe transmitter and the indicator.

Also, identify where in the circuit the communicator may be connected and still be able to “talk” withthe smart instrument. What advantage(s) may there be in being able to connect the communicator atdifferent points in the circuit?

file i00400

26

Question 14

Write equations expressing the total voltage sensed by the indicating instrument, as functions of thevoltages shown in the diagrams. Assume that all junctions form the same thermocouple type (e.g. all typeJ, all type K, etc.):

V1

V2

V3

V4

V5

Vref

Vmeter = ???

Series thermocouple junctions

V1

V3

Vref

Vmeter = ???Parallel thermocouple junctions

V2

file i00399

Question 15

Differential thermocouple circuits are used to measure the difference in temperature between two points:

T1 T2

Indicator

Does the indicating instrument require reference junction compensation or not? Explain your answer.file i00401

27

Question 16

When using a thermocouple calibrator (simulator), where you simply set it to simulate a thermocoupleat a specified temperature, is it important to use the correct thermocouple or extension wire to connect thecalibrator with the transmitter, or is the wire type irrelevant?

Z S

4-20 mA cable

COMA

V

V A

AOFF

mA

Power supply

24 V

0

1 2 3

4 5 6

7 8 9

Enter

oF

Calibrator

AmmeterThermocouplewire

transmitter

Loop-poweredtemperature

J K E T S

K

oF

oC

???

Be sure to explain your answer, based on the presence of dissimilar-metal junctions and junction-compensation circuitry in both the calibrator and transmitter.

file i00396

Question 17

Terminal blocks used in thermocouple circuits are designed to be isothermal. For example, the dual-terminal connection block found inside a thermocouple “head” box is a prime example of an isothermalblock.

Explain what this term “isothermal” means, how it is physically designed, and also why it is an importantfeature.

file i00402

Question 18

Question 19

Question 20

28

Question 21

Read pages 10-13 of the Nuclear Regulatory Commission’s “Three Mile Island – A Report to theCommissioners and to the Public” for an overview of the nuclear reactor power generating system, andpages 30-31 (Section 5 of the accident narrative) highlighting instrument technicians’ roles on the day of theMarch 28, 1979 accident, then answer the following questions:

The normal operating temperature of water inside the reactor vessel is 575 oF, but yet the water doesnot boil even when the reactor is operating at full power. Explain how boiling is prevented with such a highoperating temperature.

At the heart of the accident was a stuck-open pressure relief valve called a PORV. This open valve allowedcooling water to escape from the primary (reactor) coolant loop, eventually leading to a condition whereabout half of the reactor core (normally submerged in cooling water) was uncovered. Instrument technicianswere sent to manually measure reactor core temperatures by taking electrical measurements off the “in-core”thermocouple wires (pp. 30-31 of the Report). Based on what you know about thermocouples, explainexactly the steps these instrument technicians would have taken to obtain the temperature measurements.

According to the Report, what subsequent action(s) were taken following the instrument technicians’measurements?

file i03996

29

Question 22

Determine what type of temperature sensor is shown in this pictorial diagram, and then sketch wiresshowing how to correctly connect the sensor to the temperature transmitter:

Loop power

Sensor

Temperaturetransmitter

24 VDC power supply

Panel-mounted indicator(1-5 VDC input)

Temperature sensor Blue

Red

250 Ω± 0.1%

Note what types of metal each of the connecting wires should be (e.g. copper, chromel, alumel,constantan, iron, platinum, etc.).

file i03997

30

Question 23


Loop power

Sensor


24 VDC power supply

Panel-mounted indicator

Temperature sensor Red

Yellow

(4-20 mA input)


file i03998

31

Question 24


Loop power

Sensor


24 VDC power supply

Panel-mounted indicator

Temperature sensor Red

(4-20 mA input)

White

White


file i03999

32

Question 25

The sensor in this diagram is a platinum RTD. Sketch wires showing how to correctly connect this RTDsensor to the temperature transmitter so that the wire resistance is canceled and will produce absolutely nomeasurement error:

Loop power

Sensor


24 VDC power supply

Panel-mounted indicator(4-20 mA input)

Platinum RTD


file i04000

33

Question 26

Given the choice between these two wiring options (keeping the transmitter close to the process versusfar away), which is best, and why?

Yel RedType K

thermocouple(Yellow + Red

wires)

Head

Z S

Transmitter4-20 mA cable

Indicator

Extension wire

(long) (short)

Yel RedType K

thermocouple(Yellow + Red

wires)

Head

Z S

Transmitter

4-20 mA cable

IndicatorExtension wire

(long)(short)

file i00392

34

Question 27

Suppose a precision voltage source (“precision potentiometer”) is used to simulate a thermocouple signalinto a temperature transmitter as such:

Loop power

Sensor


0

1 2 3

4 5 6

7 8 9

Enter

J K E T S

oF

oC

mV

mV

Millivolt source

To 24 VDCloop power

Calculate the amount of voltage this precision source would have to output in order to simulate thefollowing thermocouple temperatures:

• Simulate 112 oF ; source voltage =



Assume an ambient temperature near the transmitter of 75 oF, and a type K configuration with referencejunction compensation active.

Examine the keypad of the calibration instrument being used here, and determine how this three-pointcalibration could be done much easier than looking up millivoltage values in thermocouple tables.

file i04001

35

Question 28

Suppose a decade box resistance unit is used to simulate an RTD signal into a temperature transmitteras such:

Loop power

Sensor


To 24 VDCloop power

Decade resistance box

61 0 4 3

ohmstenshundreds tenths hundredths

Calculate the amount of resistance this decade box would have to be set to in order to simulate thefollowing RTD temperatures:

• Simulate 84 oF ; resistance =



Assume a 100 ohm platinum (α = 0.00385 Ω/ΩoC) RTD configuration for the transmitter.file i04002

36

Question 29

Suppose you walk up to this thermocouple, installed to measure the temperature of an enclosed processvessel, and connect a sensitive voltmeter to the terminals at the junction head:

Red

Head Z S

Transmitter

4-20 mA cable

Process vessel

COMA

V

V A

AOFF

mV

(long length of extension cable)

Temp = ???

Ambient temp = 87 oF

Ambient temp = 71 oFVio

First, determine which lead of the voltmeter should contact which lead of the thermocouple (red tored?), then determine the temperature of the process vessel if the measured voltage is 15.830 mV.

file i04003

37

Question 30

Calculate the following voltage drops in this circuit assuming a thermocouple tip temperature of 718o

F, perfect calibration of all other instruments in the loop (Temp. range = 500 to 1000o F; current range =4 to 20 mA), and a DC power supply voltage of exactly 28 volts:

+

-

250Ω

+

L1

L2

G

ES 120VAC60 Hz

Fieldpanel

Field process area

Tag number Description Manufacturer Model Calibration Notes

Loop Diagram: Revised by: Date:

8

9

TB64 TB27

15

16

250 Ω resistor n/a +/- 0.1 %

1-5 VDC

Control roomP5 Fieldpanel

14

14

CBL 9 CBL 41

P30

CBL 223

4

TB40

TT

10

11

+

-14TI

CBL 10

14a14b

TY-14a,b

TIR-14

TYTY

TI-14

+

-

14TE

TE-14 Type K thermocouple Gordon Ungrounded tip

Local indicator 500 - 1000o F

T. Couple April 1, 2002#3 retort temperature

TT-14 Temperature transmitter Rosemount 444 500 - 1000o F4-20 mA

EurothermPaperless chart recorder

1 - 5 VDC

TIR

ES +28 VDC

ES DC Gnd

250Ω

• Voltage between terminals TB64-8 and TB64-9 =



Also, calculate the amount of voltage across the transmitter’s output terminals when the thermocoupleis measuring 1000o F.

file i00393

Question 31

Question 32

Question 33

Question 34

38

Question 35

Question 36

Question 37

Question 38

Question 39

Question 40

Question 41

Read and outline the “Non-Contact Temperature Sensors” section of the “Continuous TemperatureMeasurement” chapter in your Lessons In Industrial Instrumentation textbook. Note the page numberswhere important illustrations, photographs, equations, tables, and other relevant details are found. Prepareto thoughtfully discuss with your instructor and classmates the concepts and examples explored in thisreading.

file i04017

Question 42

Read and outline the “Temperature Switches” section of the “Discrete Process Measurement” chapter inyour Lessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i04004

Question 43

Explain what the following “ladder-logic” circuit does, and identify the meaning of each symbol in thediagram:

L1 L2

TSH

TSL

Temp. high

Temp. low

TSHH

Cooling watersolenoid

file i00364

39

Question 44

Two temperature switches sense the temperature inside an electrically-heated oven, each one with itsown “trip” value. Examine the schematic diagram for the control circuit, and then explain how it is supposedto function:

L1 L2

CR1

CR1

250 oF 285 oF

Heating element

file i04005

Question 45

The “Site Programmable Transmitter” (model SPT) manufactured by Moore Industries is an electronicdevice capable of receiving input from an RTD or thermocouple, and outputting a discrete switch contactsignal useful as an alarm (in addition to outputting an analog 4-20 mA signal representing temperaturemeasurement):

SPTView

Select

Ready Trip Input

AC power plug

AC light bulbT/C

Yel Red

Based on analysis of this instrument’s datasheet, sketch the necessary wire connections so that the lightbulb will turn on when a certain temperature limit is exceeded. Also, determine what type of thermocoupleis shown in the diagram.

file i04009

40

Question 46

Read and outline the “Temperature Standards” section of the “Instrument Calibration” chapter inyour Lessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i04006

Question 47

Read and outline the “Temperature Sensor Accessories” section of the “Continuous TemperatureMeasurement” chapter in your Lessons In Industrial Instrumentation textbook. Note the page numberswhere important illustrations, photographs, equations, tables, and other relevant details are found. Prepareto thoughtfully discuss with your instructor and classmates the concepts and examples explored in thisreading.

file i04007

Question 48

Read portions of the Rosemount datasheet for high-temperature thermocouple assemblies (document00813-0401-2654) and answer the following questions:

Identify some of the different materials used in the construction of “protective tubes” (thermowells)offered by Rosemount for high-temperature measurement applications.

Ceramic thermowells may be damaged by a phenomenon called thermal shock. Explain what “thermalshock” is, how it may occur during thermocouple installation, and what precaution(s) to take to avoid this.

What are some of the factors to consider when selecting a thermowell material for a particular processapplication?

Explain what a multipoint gradient thermocouple assembly is, and what one might be used for.file i04010

Question 49

Read the datasheet for “The WORM” flexible temperature sensor marketed by Moore Industries andanswer the following questions:

Explain how this sensor design ensures good thermal contact with the thermowell.

Identify some of the sensor types available in this product line.file i04008

41

Question 50

The Stefan-Boltzmann Law of radiated energy tells us that the rate of heat lost by radiant emissionfrom a hot object is proportional to the fourth power of the absolute temperature:

dQ

dt= eσAT 4

Where,dQdt

= Radiant heat loss rate, in watts (W)e = Emissivity factor, unitlessσ = Stefan-Boltzmann constant (5.67 × 10−8 W / m2 · K4)A = Surface area, in square meters (m2)T = Absolute temperature, Kelvin (K)

Algebraically manipulate this equation to solve for T in terms of all the other variables.file i00421

Question 51

Question 52

Question 53

Question 54

Question 55

Question 56

Question 57

Question 58

Question 59

Question 60

Question 61

Calculate the pressure of gas inside an enclosed vessel using the Ideal Gas Law, if the vessel volume is1500 liters, the vessel and gas temperature is 125 oF, and the molecular quantity of gas inside the vessel is80 moles. Express this pressure in units of atmospheres and also kPaG (kilopascals, gauge pressure).

file i04014

42

Question 62

A gas enclosed inside a chamber may act as a primitive thermometer, based on the Ideal Gas Law:

PV = nRT

Where,P = Absolute pressure (atmospheres)V = Volume (liters)n = Gas quantity (moles)R = Universal gas constant (0.0821 L · atm / mol · K)T = Absolute temperature (K)

Suppose a hollow metal chamber filled with air connects to a pressure gauge through a capillary tube (atube with a very small internal diameter). As the chamber heats and cools, the air pressure inside changesas well:

Spherical chamber

Capillary tube

Pressure gauge

At room temperature (20 oC), the chamber’s air pressure is 1 atmosphere. How high would the chamber’stemperature have to be raised in order to increase the internal air pressure to 2 atmospheres? Supposingthe pressure gauge is calibrated to read in units of PSIG, how high would it register at this temperature?

What class of filled-bulb temperature instrument does this arrangement represent? Class I? Class II?Class III? Class V?

file i04013

Question 63

Read portions of the Moore Products “Nullmatic” pneumatic temperature transmitter service manual(model 33) and answer the following questions:

Identify the upper operating temperature limit of this instrument, and compare this against commonthermocouples.

Determine whether this is a force-balance or a motion-balance instrument, based on an examination ofits cut-away diagram.

file i04016

43

Question 64

Suppose two temperature-measuring instruments are measuring the exact same process temperature,providing redundant indications inside a control room:

Processvessel

oF

(voltmeter)

Control room

oF

(bourdon tube gauge)bulb

thermocouple

Operator

Both instruments are rather primitive: the thermocouple indicator is nothing more than an analogmilli-voltmeter movement, and the filled-bulb system is a Class V arrangement with a simple bourdon tubepressure gauge mechanism used as the temperature indicator.

Now, suppose that the operator accidently bumps the thermostat in the control room, causing thecontrol room’s ambient temperature to increase by 20o F. Assuming the process vessel temperature remainsthe same, describe the effect of elevated control room temperature on both temperature indicators, beingsure to explain why for both cases.

file i02969

44

Question 65

How many reference junctions does this thermocouple circuit have?

Yel Red

Type Kthermocouple

(Yellow + Redwires)

YelRed

extension wire extension wire

IndicatorType KX Type KX

file i02972

45

Question 66

One simple way to build a “reference junction compensation” circuit is to use a bridge with a thermistor(temperature-sensitive resistor) in one arm like this:

VoltmeterCu

Temperature indicatorinstrument

CuT

Cu

C

+ -

As the terminal block warms up and cools down, the resistance of the thermistor will change, alteringthe balance of the bridge to add the appropriate amount of voltage in series with the meter circuit to cancelout the millivoltage generated by the thermocouple wires connecting with copper wires at the terminal block(the “reference junction”).

Given the type of thermocouple shown here (type T, with copper and constantan wires), the voltmeter’spolarity, the orientation of the battery in the bridge circuit, and the thermistor’s location in the bridge circuit,does the thermistor have to have a positive temperature coefficient (resistance increases as temperatureincreases) or a negative temperature coefficient (resistance decreases as temperature increases)?

Hint: begin your solution to the problem by properly identifying the source of the problem itself –determine the polarity of the reference junction voltage, so you will know which way the bridge’s outputvoltage must be oriented to cancel it out.

file i00384

Question 67

Read selected portions of the US Chemical Safety and Hazard Investigation Board’s analysis of the 1998chemical manufacturing incident at the Morton International manufacturing facility in Paterson, New Jersey(Report number 1998-06-I-NJ), and answer the following questions:

Based on the incident summary and key findings presented on pages 1 through 5, summarize how theprocess is supposed to work and then describe what went wrong to produce the explosion.

A graph on page 31 of the report contrasts heat production of the chemical reaction versus heat removalof the process cooling system. Identify where the “danger” point is on this graph, and explain why it isdangerous based on your knowledge of specific heat and heat transfer.

The chemical reactions involved in this process were primarily exothermic. Explain what this termmeans, and why it is important to the cause of this accident.

file i04011

46

Question 68

Read selected portions of the US Chemical Safety and Hazard Investigation Board’s analysis of the 1998chemical manufacturing incident at the Morton International manufacturing facility in Paterson, New Jersey(Report number 1998-06-I-NJ), and answer the following questions:

Pages 14 and 16 of the report describe the construction of the “kettle” batch process used by Mortonto produce “Yellow 96” dye. Page 16 in particular shows a simplified P&ID of the batch process. Based onwhat you find in this section of the report, identify and explain all the modes of heat addition to and heatremoval from the process vessel. Also identify all measurement instrumentation for the kettle.

An important factor leading to this event was a failure to heed established Management of Change(MOC) procedures, as described on page 7, on pages 45-46, and also on pages 57-58. Explain what“Management of Change” refers to and why it is important for process safety.

file i04012

Question 69

The reference manual for the Rosemount model 3144 temperature transmitter states that the default(factory) configuration for this transmitter is for the failure mode to be “high”. Explain what this means,and why the “failure mode” is an important parameter for a thermocouple instrument.

Also, comment on the “NAMUR” signal levels differentiating a saturated condition from a detectedfailure, and why this standard might be important in a control system.

file i04015

47

Question 70

Determine the following parameters for type J, type K, type E, type T, type S, and type R thermocouples.This includes the American color codes for individual wires as well as cable jackets:

• Type J• Positive wire metal type: – Color:• Negative wire metal type: – Color:• Thermocouple-grade cable jacket color:• Extension-grade cable jacket color:

• Type K• Positive wire metal type: – Color:• Negative wire metal type: – Color:• Thermocouple-grade cable jacket color:• Extension-grade cable jacket color:

• Type E• Positive wire metal type: – Color:• Negative wire metal type: – Color:• Thermocouple-grade cable jacket color:• Extension-grade cable jacket color:

• Type T• Positive wire metal type: – Color:• Negative wire metal type: – Color:• Thermocouple-grade cable jacket color:• Extension-grade cable jacket color:

• Type S• Positive wire metal type: – Color:• Negative wire metal type: – Color:• Thermocouple-grade cable jacket color:• Extension-grade cable jacket color:

• Type R• Positive wire metal type: – Color:• Negative wire metal type: – Color:• Thermocouple-grade cable jacket color:• Extension-grade cable jacket color:

Additionally, rank these thermocouples in order of maximum temperature, from lowest to highest.file i00389

48

Question 71

Read “Case Number 1” (pages 1-4) of the US Chemical Safety and Hazard Investigation Board’s safetybulletin on “Management of Change” (Bulletin number 2001-04-SB) discussing the 1998 coker fire at theEquilon refinery in Anacortes (Washington), and answer the following questions:

Explain in general terms what happened in the Coker unit of the refinery following a power outage, thatled to this accident. Specifically, identify how temperature measurement played a crucial role in the decisionto drain the coke drum.

Identify how the temperature sensors would have had to be built differently in order to provide betterinformation to operations about the status of the coke drum under these abnormal conditions. Explain whytheir existing design was adequate to measure temperature under normal operating conditions.

Page 2 describes how a similar incident (though not lethal) occurred in 1996. Describe the follow-up tothat incident, and how better “Management of Change” (MOC) procedures might have prevented the 1998disaster.

file i04253

Question 72

Supposed we wished to design a precise electronic instrument to measure temperature from athermocouple’s millivoltage signal. This instrument would be based upon the principle of a voltmeter:the more voltage applied to the input terminals, the greater the indication. The voltmeter scale, of course,would be labeled in units of degrees (Fahrenheit or Celsius, your choice) rather than “volts.”

VoltmeterCu

Cu

Thermocouplewires connect

here


A simple instrument designed exactly like this would actually be affected by the temperatures in twodifferent locations, rather than generate an indication reflecting the process temperature alone. What is theother temperature that has an effect on the indication, and why does it have the effect it does?

How could this problem be overcome, so that our instrument’s indication becomes purely a function ofthermocouple temperature and nothing else? Be creative!

file i00383

Question 73

Question 74

Question 75

Question 76

49

Question 77

Question 78

Question 79

Question 80

50

Question 81

Describe at least two common thermocouple problems, and how they may be diagnosed in the field.

This is a graded question: you will be graded on accuracy and originality (no plagiarized answers!).file i00041

51

Question 82

RTDs are often used inside of bridge circuits to convert a temperature measurement into a voltage:

R1

R3

+−Vexcitation

Measuringinstrument

RRTD

R2

Assume that the bridge is balanced when the RTD is at its lower range value (LRV). Identify:

• The polarity of the voltage across all bridge resistors.• The polarity of the voltage sensed by the measuring instrument as temperature increases toward the

URV.• Which variable resistance (R1 or R3) adjusts zero.• Which variable resistance (R1 or R3) adjusts span.• One electrical fault (open or short) resulting in a positive over-range (> 100 % temp.) reading.• One electrical fault (open or short) resulting in a negative over-range (< 0 % temp.) reading.

Also, explain why you have identified the zero and span adjustment resistors as such:


52

Question 83

Design a thermistor circuit that produces an increasing output voltage with increasing temperature.Hint: the topology of the circuit may be as simple as this:

+−Vsource

Vout

R1

R2

You will need to choose which resistor (R1 or R2) to make the thermistor and which to make fixed,and also choose which type of temperature coefficient the thermistor will have (either positive or negative).After making these choices and drawing your circuit below, explain how it works (i.e. what happens to allthe voltages and currents as temperature increases):


53

Question 84

Shell-and-tube heat exchangers are often heated by steam, with the steam condensing to water inside theshell of the exchanger. Cold product flowing in one end of the tubes picks up heat from the steam/condensateand leaves the other end of the tubes at a higher temperature:

Cold productin

Hot productout

Condensate out

Steam in

Control valve

Heatexchanger

Water

Steam

It is sometimes necessary to know the temperature of the steam/condensate inside the heat exchangershell. The obvious way to measure this is by installing a temperature sensing element (thermocouple,RTD, etc.) in the shell. However, there is another, not so obvious, way of measuring steam/condensatetemperature: we could install a pressure sensing element to measure steam pressure inside the shell like this:

Steam in

Condensate out

PT

Pressure transmitter

Signal out

Identify and explain what principle of physics allows us to precisely equate the pressure inside theexchanger shell with the temperature of the steam and condensate.


54

Question 85

The Stefan-Boltzmann Law of radiated energy tells us that the rate of heat emission (dQdt

, in Watts)emitted by a hot object is proportional to the fourth power of the absolute temperature (T , in Kelvin):

dQ

dt∝ T 4

Note that I have not written this as an actual equation (“equal to”) but rather as a proportionality.

The Stefan-Boltzmann Law gives us a basis for inferring temperature from the optical radiation emittedfrom an object. Identify and explain what factors beside temperature (T ) affect the amount of radiationreceived by a sensor from a hot object. In other words, what else must we know before we can accuratelyinfer the temperature of any particular hot object by its emitted radiation?


55

Question 86

The amount of voltage between two different “hot” conductors of a Y-type three-phase AC power systemmay be represented in the form of a vector diagram, where the lengths of lines represent voltage magnitudesand the directions indicated phase shift. The following vector diagram shows the magnitudes of three voltages(277 volts AC each), phase-shifted 120 degrees from each other:

VA = 277 V

V B =

277

V

VC = 277 V

120o

120o

120 o

B

A

C

V AB = ???

VB

C = ???

VAC = ???

Use the trigonometric “Law of Sines” to solve for the length of the sides represented by dashed lines,representing the voltage between points A and B, B and C, and A and C, respectively. Be sure to show allyour work!

VAB = VBC = VAC =

Hint: the Law of Sines allows us to solve for any one unknown side length or angle for any kind oftriangle, even if it isn’t a right triangle! It tells us that for any triangle, the sine of an angle divided by thelength of that angle’s opposite side will be a constant value:

X

Y

Zy

x

z

sinx

X=

sin y

Y=

sin z

Z

file i03298

56

Question 87

The resonant frequency of a simple inductor-capacitor (LC) circuit may be calculated using the followingequation:

fr =1

2π√

LC

Determine two different ways to increase the resonant frequency of an LC circuit according to the aboveequation, and explain why each method works.

file i03521

57

Question 88

Use Kirchhoff’s Voltage Law to calculate the magnitude and polarity of the voltage across resistor R4

in this resistor network:

R1

R2

R3

R4

R5

R6

10 V

1 V

2.5 V

25 V

8 V

7 V

file i02526

58

Question 89

What will happen to the voltage drops across each resistor in this circuit if resistor R4 fails shorted (e.g.a solder bridge forms across R4 during assembly)?

Printed circuit board withsurface-mount resistors

R1

R2

R3

R4

+ -

Powersupply

• VR1 = (increase, decrease, or stay the same)




Be sure to explain your reasoning for the answers you give!

file i03153

59

Question 90

In this automotive fuel level sensing circuit, a current mirror is supposed to maintain a constant current(about 25 to 26 mA) through the fuel level sensor, which is nothing more than a variable resistance (rheostat)that changes with fuel level. The voltage dropped across this sensor resistance is then sent to a fuel gauge:a voltmeter with the scale calibrated in gallons of fuel level:

12 V

Ignitionswitch

R1

Fuel levelsensor

5 Ω = Empty260 Ω = Full

Q1 Q2

TP1

TP2

TP3

TP4

440 Ω

Fuel gauge(voltmeter)

Current mirror circuit

There is a problem in this circuit, though. The fuel gauge reads empty even when you know the fueltank is completely full. You take two DC voltage measurements to begin your troubleshooting: +12 voltsbetween TP4 and ground, and 0 volts between TP3 and ground.

From this information, identify two possible faults (either one of which could account for the problemand all measured values in this circuit), and also identify two circuit elements that could not possibly be toblame (i.e. two things that you know must be functioning properly, no matter what else may be faulted).The circuit elements you identify as either possibly faulted or properly functioning can be wires, traces, andconnections as well as components. Be as specific as you can in your answers, identifying both the circuitelement and the type of fault.

• Circuit elements that are possibly faulted1.2.

• Circuit elements that must be functioning properly1.2.

file i03183

60

Question 91

Lab Exercise

Your team’s task is to set up a temperature measurement loop using an electronic thermocouple andand an RTD. Ambient air temperature is the suggested process variable to measure. Other temperaturevariables are open for consideration, though. Each instrument in the loop should be labeled with a propertag name (e.g. “TT-37” for a temperature transmitter), with all instruments in each loop sharing the sameloop number. Write on pieces of masking tape to make simple labels for all the instruments and signal lines.

Each student must configure a “smart” transmitter for thermocouple (T/C) input, and again for RTDinput, demonstrating how to calibrate it for both sensor types. The indicator (or indicating controller) mustregister in the proper engineering units (e.g. a temperature transmitter calibrated to a range of 50 to 90degrees F should actually register 50 to 90 degrees F back at the control room display). Each team membershould choose their own (unique) temperature calibration range.

Additionally, each team member must simulate a thermocouple at some specified temperature toa thermocouple transmitter by sourcing a precise amount of millivoltage to the input terminals of thetransmitter (configured for thermocouple input). This will require consulting a thermocouple table to findthe voltage produced by a thermocouple junction at that temperature, and also the equivalent referencejunction voltage at ambient temperature (measured by a thermometer), calculating the necessary voltage toinput to the transmitter’s terminals. The purpose of this exercise is to learn how to simulate thermocouplesignals without the benefit of a self-compensating thermocouple “calibrator” device – just a precision low-voltage supply.

Each student must diagnose a fault in the system within a 5-minute time limit, correctly identifying boththe general location and nature of the fault, and logically justifying all diagnostic steps taken. Additionaltime will be given to precisely locate and rectify the fault following successful diagnosis within the allottedtime. Failure to identify both the general location and nature of the fault within the allotted time, and/orfailing to demonstrate rational diagnostic procedure will disqualify the effort, in which case the student mustre-try with a different fault. Multiple re-tries are permitted with no reduction in grade.

Objective completion table:

Performance objective Grading 1 2 3 4 TeamComponent selection and testing mastery – – – –

Loop diagram and inspection mastery – – – –Loop calibration – T/C (± 0.5% of span) mastery – – – –Loop calibration – RTD (± 0.5% of span) mastery – – – –

Millivolt simulation of T/C mastery – – – –Troubleshooting (5 minute limit) mastery – – – –

Lab question: Diagnosis proportional – – – –Lab question: Instruments proportional – – – –

Lab question: Math proportional – – – –Lab question: Tools/safety proportional – – – –

Lab questions (reviewed between instructor and student team in a private session)

• Diagnosis• Explain what will happen (and why) if a thermocouple circuit develops a short at the transmitter input

terminals (where the extension wires connect)• Explain what will happen (and why) if an RTD circuit develops a short at the transmitter input terminals

(where the lead wires connect)• Identify and explain common temperature sensor problems (thermocouple, RTD, and thermistor)• Identify what burnout mode is for a thermocouple temperature transmitter, and why it is necessary

61

• Explain why it is a bad idea to operate a portable radio transmitter (“walkie-talkie”) near an unshieldedthermocouple or RTD circuit

• Explain what will happen (and why) if the 250 ohm resistor fails open in the transmitter circuit• Explain what will happen (and why) if the 250 ohm resistor fails shorted in the transmitter circuit• Explain what will happen (and why) if the transmitter cable fails open• Explain what will happen (and why) if the transmitter cable fails shorted• Explain what will happen (and why) if loop power supply voltage is too low• Identify what things may be determined about a malfunctioning measurement loop from a single

measurement of the 4-20 mA process variable signal (e.g. suppose the indicator fails to accuratelyregister the temperature applied to a transmitter – how could a loop current measurement help you inyour diagnosis?)

• Explain what will happen (and why) in a temperature level control loop if the thermocouple wires tothe transmitter are disconnected. Assume the controller is in automatic mode when this happens, andthat the transmitter is configured for upscale burnout.

• Explain what will happen (and why) in a temperature level control loop if the thermocouple wires tothe transmitter are disconnected. Assume the controller is in automatic mode when this happens, andthat the transmitter is configured for downscale burnout.

• Instruments• Identify color codes and wire metals for a type J thermocouple• Identify color codes and wire metals for a type K thermocouple• Identify color codes and wire metals for a type T thermocouple• Identify color codes and wire metals for a type S thermocouple• Identify color codes and wire metals for a type E thermocouple• Rank types J, K, T, S, and E thermocouples according to their maximum temperatures• Explain what cold-junction (or reference junction) compensation is and why it is necessary• Explain what a thermowell is and its purpose in an industrial temperature measurement application• Explain how to distinguish thermocouple-grade wire from extension-grade wire• Explain the operations and purposes of 2-wire, 3-wire, and 4-wire RTD circuits

• Math (no calculator allowed!)• Calculate the correct loop current value (mA) given a temperature transmitter calibration range and

an applied temperature• Calculate the temperature applied to a transmitter given a calibration range and the measured loop

current value• Calculate the percentage of span error for a transmitter given a calibration range and an As-Found

calibration table• Calculate the allowable temperature error for a transmitter given an allowable percentage of span error

and a calibration range• Convert between different temperature units, without relying on the use of a reference for conversion

formulae (i.e. you must commit the formulae to memory)

62

• Tools/Safety• Explain how you can use water as a temperature calibration standard• Explain how a handheld temperature calibrator (such as the Fluke model 744) simulates a thermocouple:

exactly what type of signal does it output to the instrument under test?• Explain how a handheld temperature calibrator (such as the Fluke model 744) simulates an RTD: exactly

what type of signal does it output to the instrument under test?• Identify how to connect a handheld temperature calibrator (such as the Fluke model 744) to a

temperature transmitter to simulate a 3-wire RTD• Identify how to connect a handheld temperature calibrator (such as the Fluke model 744) to a

temperature transmitter to simulate a 4-wire RTD• Identify and explain what a dry block temperature calibrator is• Demonstrate how to shut off and tag out electrical power to your loop instruments• Identify where the danger tags are kept (for tagging out devices)• Explain how to safely check the calibration of an RTD transmitter in a temperature control loop without

causing the controller to over-react to the resistance values you apply to the transmitter as part of yourcalibration check.

file i00378

63

Question

92

Loop

dia

gra

mte

mpla

te

Description Manufacturer Model Notes


Tag # Input range Output range

64

Loop diagram requirements

• Instrument “bubbles”• Proper symbols and designations used for all instruments.• All instrument “bubbles” properly labeled (letter codes and loop numbers).• All instrument “bubbles” marked with the proper lines (solid line, dashed line, single line, double lines,

no lines).• Optional: Calibration ranges and action arrows written next to each bubble.

• Text descriptions• Each instrument documented below (tag number, description, etc.).• Calibration (input and output ranges) given for each instrument, as applicable.

• Connection points• All terminals and tube junctions properly labeled.• All terminal blocks properly labeled.• All junction (“field”) boxes shown as distinct sections of the loop diagram, and properly labeled.• All control panels shown as distinct sections of the loop diagram, and properly labeled.• All wire colors shown next to each terminal.• All terminals on instruments labeled as they appear on the instrument (so that anyone reading the

diagram will know which instrument terminal each wire goes to).

• Cables and tubes• Single-pair cables or pneumatic tubes going to individual instruments should be labeled with the field

instrument tag number (e.g. “TT-8” or “TY-12”)• Multi-pair cables or pneumatic tube bundles going between junction boxes and/or panels need to have

unique numbers (e.g. “Cable 10”) as well as numbers for each pair (e.g. “Pair 1,” “Pair 2,” etc.).

• Energy sources• All power source intensities labeled (e.g. “24 VDC,” “120 VAC,” “20 PSI”)• All shutoff points labeled (e.g. “Breaker #5,” “Valve #7”)

65

Sam

ple

Loop

Dia

gra

m(u

sing

asin

gle

-loop

contro

ller)

Process areaField panel Control room panel

Controller

Resistor

I/P transducer

Control valve

I/P

ES 120 VAC

AS 20 PSI

Loop Diagram: Furnace temperature control

TT205

JB-12

TB-15

TB-15

3

4

1

2

Temperature transmitterTT-205 Rosemount 444

TE205

CP-1

TB-11

TB-11

1

2

7

Vishay 250 ΩTY-205a

TIC-205 Siemens PAC 353

TY-205b

TV-205 Fisher Easy-E 3-15 PSI

Fisher

H

N

3

4

22

21

19

18

TY205b

TY

205a

Breaker #4Panel L2

5

6Cable TY-205b

Cable TT-205 Cable TT-205

Cable TY-205b

TIC205

Revised by: Mason Neilan

TV205

Tube TV-205

Column #8Valve #15

546

0-1500oF 0-1500oF

Fail-closed

Reverse-acting control

TE-205 Thermocouple Omega Type K Ungrounded tip

Red

BlkRed

Yel Red

Blk

Red

Blk

Red

Blk

Wht/Blu

Blu Blu

Wht/Blu

Cable 3, Pr 1

Cable 3, Pr 2

Wht/Org

Org Org

Wht/Org

Blk

Red

Blk

Red

Blk

Wht

Red

Blk

Red

Blk

Upscale burnout


Date:


0-1500o F 4-20 mA

4-20 mA 3-15 PSI

0-100%

1-5 V 0-1500o F

April 1, 2007

66

Sam

ple

Loop

Dia

gra

m(u

sing

DC

Scontro

ller)

Field process area



DCS cabinet

Red

Blk

Red

Blk

Red

Blk

Fisher

Fisher


Blue team pressure loop April 1, 2009

Card 4

Card 6Channel 6

Channel 611

12

29

30

Red

Blk

TB-80

TB-80

Field panel JB-25

TB-52

TB-52

PT-6 Pressure transmitter Rosemount 3051CD 0-50 PSI 4-20 mA

PIC6

PT6

Cable 4, Pr 1

Cable 4, Pr 8

1

2

15

16

Cable PT-6

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Cable PV-6

11

12

11

12PY6

AS 20 PSI

PV6

0-50 PSI

I/P

0-50 PSI

846

Emerson DeltaV 4-20 mA 4-20 mA HART-enabled inputPIC-6

PY-6

PV-6

I/P transducer

Controller

Control valve Vee-ball

4-20 mA 3-15 PSI

3-15 PSI 0-100% Fail-open

Duncan D.V.

Tube PV-6

Cable PT-6

Cable PV-6

Analog input

Analogoutput

Direct-acting control

H

L

67

Sam

ple

Loop

Dia

gra

m(u

sing

pneum

atic

contro

ller)




LT24

In

H

LOut

C

D

A.S. 21 PSI

Tube LT-24a Tube LT-24b

A.S. 21 PSI

Process areaBulkhead panel

14

B-104Control panel CP-11

Tube LV-24

LV24

Tube LV-24

Supply

LIC

24

Tube LV-24

(vent)

Sludge tank level control I. Leaky April 1, 2008

LT-24 Level transmitter Foxboro 13A 25-150 "H2O 3-15 PSI

3-15 PSI 3-15 PSIFoxboroLIC-24 130

LV-24 Fisher Easy-E / 667 3-15 PSI 0-100% Fail closedControl valve

Controller

file

i00654

68

Question 93

Connect a loop-powered temperature transmitter (4-20 mA output) to a DC voltage source and a metersuch that the meter will indicate a increasing signal when the temperature-sensing element is heated. Allelectrical connections must be made using a terminal strip (no twisted wires, crimp splices, wire nuts, springclips, or “alligator” clips permitted).

This exercise tests your ability to properly connect power to a loop-powered temperature transmitter,connect multiple batteries together to achieve the required total supply voltage, identify different types ofthermocouples and RTDs, properly connect either a thermocouple or an RTD to the transmitter, conditionthe electrical signal (if necessary) so the meter can properly register it, properly connect an analog meterinto the circuit, and use a terminal strip to organize all electrical connections.

- +

+ -

Meter

transmitter

Terminal strip

Resistor+ -

Batteries

TemperatureThermocouple or RTD

The following components and materials will be available to you during the exam: assorted 2-wire4-20 mA temperature transmitters calibrated to ranges inclusive of room temperature ; an assortmentof thermocouples and RTDs ; terminal strips ; lengths of hook-up wire ; 250 Ω (or approximate)resistors ; analog meters ; battery clips (holders).

You will be expected to supply your own screwdrivers and multimeter for assembling and testing thecircuit at your desk. The instructor will supply the battery(ies) to power your circuit when you are readyto see if it works. Until that time, your circuit will remain unpowered.

Meter options (instructor chooses): Voltmeter (1-5 VDC) Ammeter (4-20 mA)

Sensor type (instructor chooses): Thermocouple RTD

Study reference: the “Analog Electronic Instrumentation” chapter of Lessons In IndustrialInstrumentation, particularly the sections on loop-powered transmitters and current loop troubleshooting.Also, the “Continuous Temperature Measurement” chapter of the same textbook, particularly the sectionson thermocouples and RTDs.

file i03775

69

Answers

Answer 1

Answer 2

Answer 3

Answer 4

Answer 5

Answer 6

Answer 7

Partial answer:

Emeter = Emeas − Eref + Ecomp

Answer 8

In the calibration circuit, there is not a trace of thermocouple wire to be found. Instead, all wires aremade of copper. This presents a problem for us because the temperature instrument has a reference junctioncompensation circuit built in, which at this point is compensating for a reference junction millivoltagethat doesn’t exist. The instrument actually “sees” the series combination of the potentiometer’s outputvoltage (Epotentiometer) and its own internally-generated compensation voltage (Ecompensation), not thepotentiometer voltage by itself. This is why we cannot simply set the potentiometer to the millivoltagecorresponding to our calibration temperature point and adjust the instrument to read the same.

I’ll let you figure out exactly how to work around this problem!

70

Answer 9

Partial answer:

Cu+ -

TC wire

TC wire


Cu

+

-

+

-Einstrument

Ereference

Emeasurement

(primitive)

Equation: Emeasurement - Ereference = Einstrument

Cu+ -

TC wire

TC wire


Cu

+

-

+

-

Einstrument

Ereference

Emeasurement

T

Ecompensation

+ -

Equation: Emeasurement - Ereference + Ecompensation = Einstrument

Answer 10

Partial answer:

• Type K• 300o F ; Potentiometer setting = 5.116 mV

• Type J• 400o F ; Potentiometer setting = 10.006 mV

• Type J• 250o F ; Potentiometer setting = 5.345 mV

71

Answer 11

I’ll let you explain the “high impedance” part!

One way would be to build an operational amplifier (“op-amp”) buffer circuit to power an analogvoltmeter movement. Operational amplifiers typically have input impedances in the millions or billions ofohms (the TL082, an inexpensive, general-purpose JFET-input op-amp, has a typical input impedance of1012 Ω , or 1 trillion ohms!). The circuit would look like this:

Voltmeter−

+

+V

-VTothermocouple

The op-amp senses the thermocouple’s voltage signal and duplicates that voltage level at its outputterminal, where it powers the meter movement. The current necessary for powering the meter movementcomes from the DC power supply (+V/-V) powering the op-amp, and not from the thermocouple, so thethermocouple circuit does not become “loaded” by the meter. Another benefit of this strategy is that theop-amp buffer can easily be made into a precision amplifier, permitting the use of a larger-range voltmeter:

Voltmeter−

+

+V

-VTothermocouple

99 kΩ1 kΩ

Analog voltmeter registers 1 voltfor every 10 millivolts produced

by the thermocouple

AV = 100 = 40 dB

A non-electronic solution to this problem of building a high-impedance voltmeter is the classic “null-balance” or “potentiometric” voltmeter circuit, whereby an adjustable voltage source is used to balance theincoming signal voltage to be measured, with a highly sensitive “null” meter movement indicating when thetwo voltages are equal. Then, a regular analog voltmeter reads how much voltage the adjustable voltagesource is set for in this condition of balance:

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Voltmeter

Tothermocouple

null

When the "null" meter registers precisely zero,then the potentiometer is outputting the same voltage as the thermocouple, and the voltmeterwill register that voltage.

In the balanced condition, the voltmeter movement’s current requirements are supplied by the DCvoltage source (battery), not the thermocouple. In fact this type of circuit (null-balance, or “potentiometric”)is the only type of voltage-measuring instrument hypothetically capable of attaining infinite input impedance.Its simplicity and high theoretical input impedance makes it an elegant solution to the measurement problem.

Answer 12

IE = 4.3 mA

−

+

Rsense

Rlimit

(ground)

Voltageregulator

InOut

Gnd

Rfeedback

Rbias

Out

Gnd

+V

Thermocouple

Op-amp

+V

Gnd

Amplifyingand scaling

circuitry

All arrows drawn in the direction of conventional flow

Follow-up question: how would the transmitter circuit respond to an increase in temperature sensed bythe thermocouple? How about a decrease in loop power supply voltage (24 volts → 20 volts)?

Challenge question: it is important for instrument accuracy that we make Rbias and Rfeedback resistorsrather large in value. Explain why.

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Answer 13

Circuit as it appears to AC (HART) signals sent by the communicator:

250 Ω

HART communicator

Indicator(1-5 VDC)


(HART-compatible)

(open)

Circuit as it appears to DC (4-20 mA) signals:


250 Ω

HART communicator

(HART-compatible)

4-20 mA DC

Indicator(1-5 VDC)

(open)

The communicator may be connected anywhere that places it in parallel with the transmitter terminals,from the transmitter itself all the way back to the control panel where the indicator is located!

Challenge question: a HART communicator will be able to communicate with the smart field instrumentif it is connected directly in parallel with the 250 Ω loop resistor, even though this is technically not in parallelwith the transmitter terminals. Explain why this works!

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Answer 14

Series:

Vmeter = (V1 + V3 + V5) − (V2 + V4 + Vref )

Parallel:

Vmeter =V1 + V2 + V3

3− Vref

Follow-up question: explain why swamping resistors are often added to paralleled thermocouples toimprove the accuracy of their temperature averaging:

V1

V3

Vref

Parallel thermocouple junctions

V2

with "swamping" resistorsVmeter

Answer 15

I’ll let you figure out the answer on your own!

Follow-up question: give an example of a practical use for such a thermocouple circuit.

Answer 16

Ideally, we may use any type of connection wire we wish so long as both the calibrator and the transmitterare at the exact same temperature! If the temperatures are not the same, we must be sure to use the correcttype of thermocouple wire (or extension wire) to connect the calibrator to the instrument.

Answer 17

The metal blocks into which thermocouple wires go to connect are usually made of heavy brass, and theyare physically secured to a thick ceramic (electrically insulating) base. This helps ensure the two connectionpoints are held to the same temperature.

Answer 18

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Answer 22

Partial answer:

The sensor is a type T thermocouple.

Answer 23

Partial answer:

The sensor is a type K thermocouple.

Answer 24

Partial answer:

The sensor is a three-wire RTD.

Answer 25

Partial answer:

The sensor is a two-wire RTD.

Answer 26

Keep the transmitter close to the thermocouple to minimize cost and maximize electrical noise immunity.I’ll let you explain why for each of these reasons!

Answer 27

Partial answer:

• Simulate 727 oF ; source voltage = 14.856 mV

Answer 28

Partial answer:

• Simulate 357 oF ; resistance = 169.51 Ω (calculated) 168.68 Ω (according to table)

Answer 29

The red test lead of the meter (+) should contact the violet wire of the thermocouple. The black testlead of the meter (-) should contact the red wire of the thermocouple.

Answer 30

• Voltage between terminals TB64-8 and TB64-9 = 22.512 volts



Vxmtr at maximum output = 18 volts.

Hint: if you are having difficulty analyzing this circuit, try re-drawing it in schematic form (all current-carrying components in a straight line to show their series connections).

Answer 31

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Answer 32

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Answer 43

This is an automatic cooling system with high and low temperature alarms.

Answer 44

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Answer 50

T =4

√

√

√

√

(

dQdt

)

eσA

Answer 51

Answer 52

Answer 53

Answer 54

Answer 55

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Answer 56

Answer 57

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Answer 61

Partial answer:

P = 1.422 atmospheres

Answer 62

Partial answer:

The necessary temperature to produce 2 atmospheres is 313.15 oC.

Answer 63

Partial answer:

This is a force-balance instrument.

Answer 64

The thermocouple-based instrument’s indication will decrease by approximately 20o F, while the ClassV filled system’s indication will increase slightly.

Answer 65

This circuit only has one reference junction, if you count the two terminal connections at the indicator asa single junction. The junction mid-way between the thermocouple head and the indicator is not a referencejunction because it is not a junction of dissimilar metals.

Answer 66

Hint: the copper (Cu) wire is positive and the constantan (C) wire is negative. Recall whether or notthe reference junction compensation source aided or bucked the thermocouple measurement junction, andyou will know which polarity the bridge circuit must produce as reference junction temperature increases.

Answer 67

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Answer 69

Hint: what Rosemount refers to as a “failure mode” encompasses the more specific concept of “burnout”.

Answer 70

Answer 71

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Answer 72

This instrument’s indication will be equally affected by the terminal block temperature (where thethermocouple wires connect) as it will be by the actual thermocouple temperature, since the meter’sindication depends on the differential millivoltage generated between the two junctions. At present, there isno way for the meter to “compensate” for the millivoltage generated at the terminal block so that it strictlymeasures the process (measurement junction’s) temperature.

One way is to keep the instrument’s terminal block (where the thermocouple wires connect) at a constant,known, temperature. This way, any change in voltmeter indication would have to be due to a change inactual thermocouple temperature, and no other temperature change.

Another way is to electrically compensate for the effects of the millivoltage produced where thethermocouple wires join with the instrument’s copper wires. To do this, we need to insert a source ofequal and opposite voltage in series with the meter, so that the millivoltage generated at the terminal blockwill be canceled out. To be effective, this equal and opposite voltage source must alter itself according tothe terminal block’s temperature:

VoltmeterCu

Cu

Thermocouplewires connect

here


Temperature-dependentvoltage source

Another way yet would be to equip the instrument with a regular mercury thermometer to measurethe temperature of the terminal block, and have the operator of the instrument manually offset the meter’sindication to achieve a corrected reading.

Answer 73

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Answer 81

This is a graded question – no answers or hints given!

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Answer 82


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Answer 92

Your loop diagram will be validated when the instructor inspects the loop with you and the rest of yourteam.

Answer 93

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