Portable Test Measurement

A Study

Presented to the

College Department

Don Bosco Technology Center

In Partial Fulfillment

of the Requirement for the Degree

Bachelor of Science in Electronics Engineering

By

J. William Achilles D. Young

John Paul G. Suan

Luis Mikael Arzadon

February 2015

Engr. Carlo Pilapil

Adviser

Chapter 1

THE PROBLEM AND ITS SETTING

Introduction

Don Bosco Technology Center is a Catholic institution managed and

operated by Salesian Brothers and Fathers of Don Bosco. Many years had

passed since the first opening of the college program in Don Bosco, the

Bachelor of Science in Technical Education (BSTE). The BSTE program has

three different specialization- Industrial Electronics, Furniture Technology and

Mechanical Technology. Since the opening of the program in 1995, the

institution has produced a number of graduates in the different specializations

(DBTC Student Manual p2). The need for an engineering program that

matches the need of industries prompted DBTC to take the challenge to pilot

their designed engineering program. After some adaptations on the curriculum

and with the capability of the center, the Bachelor of Science in Mechanical

Engineering major in Machine Design and Manufacturing (BSME-MDM) was

offered in year 2002. It is a five- year engineering program leading to

Mechanical Engineering with extra hands-on skills in metal Electronics, and

Computer programming. In 2003, the institution was given a permit to open

two other new engineering programs, the Bachelor of Science in Electronics

and communications Engineering (BSECE), and the Bachelor of Science in

Industrial Engineering major in Furniture Manufacturing (BSIE-FM). BSECE

graduates shall receive a certificate as Junior Engineers and have a primary

career options to work in Telecommunications Industries here and abroad and

do business related opportunities to solid state technology, and semi-

conductor applications. Industrial Engineering focuses on the Furniture Trade

Area. The primary career options of Industrial Engineering are to work in

Furniture Industry positions in facilities planning in the country hence, the

course will serve as its engineering and scientific support (DBTC Student

Manual p3).

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It is safe to say that one of the primary goals of every college and

university in the Philippines offering the program Electronics Engineering is to

produce well-rounded and competitive professionals in their field of

specialization. The Commission on Higher Education (CHED) is tasked to

supervise and guide private schools, including state universities and colleges

(SUC) to attain this goal by setting standards and mandate minimum

requirements. One of these requirements is to have well-equipped

laboratories, facilities, and equipments where students can developed their

practical skills. The laboratory equipments needed per course must be at least

five (5) sets for newly opened engineering undergraduate programs. The ideal

requirement is to have a ratio of one (1) trainer per trainee or student for the

recognized engineering undergraduate program to ensure comprehensive

learning and training.

Trainees or students having their respective trainers also need test

equipments in order to measure the output or input of the experiments. The

Portable Test Measurement (PTM) is a combination of an oscilloscope,

function generator, and a multimeter. Portable Test Measurement (PTM) can

generate its own frequency input using a function generator and its output

signal can be measured and displayed using an oscilloscope. It can also

measure resistance, voltage and current using a multimeter.

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Conceptual Background

Figure 1.1: Portable-Test-Measurement(PTM)

The Portable-Test-Measurement (figure 1.1) is an equipment which

has the capabilities of three different types of test equipment, namely, the

oscilloscope, the function generator, and the millimeter.

With the function of the oscilloscope, it is used to display and analyze

the waveform of electronic signals. In effect, the device draws a graph of the

instantaneous signal voltage (figure 1.2) as a function of time.

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Figure 1.2: Instantaneous Signal Voltage

Also, with the ability of the function generator, it would generate a

variety of simple repetitive waveforms. In addition to producing sine waves

(figure 1.3), function generators may typically produce other repetitive

waveforms including square waves (figure 1.4), pulses (figure 1.5), triangular

waveforms (figure 1.6), and sawtooth (figure 1.7). Another feature included on

many function generators is the ability to add a DC offset.

Figure 1.3: Sine wave

Figure 1.4: Square wave

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Figure 1.5: Pulse

Figure 1.6: Triangular wave

Figure 1.7: Sawtooth(ramp) wave

Finally, with the measuring capabilities of the multimeter, it measures

resistance (ohm meter), voltage (voltmeter) and current (ammeter). It can also

be used to measure capacitance, inductance, and temperature. They may

also be able to measure frequency and duty cycle (a measurement relating to

pulse systems such as fiber optic networks).

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Multimeter

Table 1.1

Measurement

Fluke 117 Multimeter

(Industry standard)

PTM-Multimeter

Minimum Maximum Minimum Maximum

Resistance

(Ohms)

0.1Ω 40.0M Ω 0.1Ω 40.0M Ω

Voltage (Volts) 0.1mV 600.0V 0.1mV 600.0V

Current

(Amperes)

0.001A 10.0A 0.001A 10.0A

Continuity 1.000 Ω 600.0 Ω 1.000 Ω 600.0 Ω

Diode test 0.001V 2.000V 0.01V 2.000V

Frequency

(Hertz)

0.1Hz 50.0 kHz 0.1Hz 50.0kHz

Capacitance

(Farad)

1nF >1000uF N/A N/A

Fluke 117 (Industry standard) vs. PTM-Multimeter comparison

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Oscilloscope

Table 1.2

Tektronix TDS3000C

Digital Oscilloscope

PTM-Oscilloscope

Bandwidth 300 MHz 100 Mhz

Rise time (typical) 1.2 nS 1.0 nS

Sample rate

(per channel)

2.5 GS/s 1.5 GS/s

Input coupling AC, DC, GND AC, DC, GND

Input impedance 1MΩ, parallel with 13pF

or 50Ω

1MΩ, parallel with 13pF

or 50Ω

Input sensitivity range 1MΩ 1mV/div – 10V/div

50Ω 1mV/div - 1V/div

1MΩ 1mV/div – 10V/div

50Ω 1mV/div - 1V/div

Position range ±5 div ±5div

Power source

(AC)

100VRMS to 240VRMS

±10%

220VRMS ±10%

Tektronix TDS3000C Digital Oscilloscope vs. PTM-Oscilloscope

comparison

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Function Generator

Table 1.3

Agilent-HP 8662A

Function Generator

PTM-Function

Generator

Frequency Range 10 kHz to 1280 Mhz 10 Hz to 1Mhz

Resolution 0.1 Hz 0.5 Hz

Level Range +13 to -139.9 dBm +10 to -50 dBm

Agilent-HP 8662A Function Generator vs. PTM-Function Generator

comparison

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Theoretical Background

Multimeter

A multimeter or a multitester, also known as a VOM (Volt-Ohm meter),

is an electronic measuring instrument that combines several measurement

functions in one unit, namely; the Voltmeter, the Ammeter, and the

Ohmmeter. A typical multimeter would include basic features such as the

ability to measure voltage, current, and resistance. A multimeter can be a

hand-held device useful for basic fault finding and field service work, or

a bench instrument which can measure to a very high degree of accuracy.

They can be used to troubleshoot electrical problems in a wide array of

industrial and household devices such as electronic equipment, motor

controls, domestic appliances, power supplies, and wiring systems.

Voltmeter

A voltmeter measures the change in voltage between two points

in an electric circuit and therefore must be connected in parallel with

the portion of the circuit on which the measurement is made (figure

1.8). In analogy with a water circuit, a voltmeter is like a meter

designed to measure pressure difference. It is necessary for the

voltmeter to have a very high resistance so that it does not have an

appreciable effect on the current or voltage associated with the

measured circuit. Modern solid-state meters have digital readouts, but

the principles of operation can be better appreciated by examining the

older moving coil meters based on galvanometer sensors.

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Figure 1.8: Voltmeter Circuit Diagram

Ammeter

An ammeter is an instrument for measuring the electric

current in amperes in a branch of an electric circuit. It must be placed

in series with the measured branch, and must have very low resistance

to avoid significant alteration of the current it is to measure (figure 1.9).

The analogy with an in-line flow meter in a water circuit can help

visualize why an ammeter must have a low resistance, and why

connecting an ammeter in parallel can damage the meter. Modern

solid-state meters have digital readouts, but the principles of operation

can be better appreciated by examining the older meters based

on galvanometer sensors.

Figure 1.9: Ammeter Circuit Diagram

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Ohmmeter

The standard way to measure resistance in ohms is to supply a

constant voltage to the resistance and measure the current through it (figure

1.10). That current is of course inversely proportional to the resistance

according to Ohm's law, so that you have a non-linear scale. The current

registered by the current sensing element is proportional to 1/R, so that a

large current implies a small resistance. Modern solid-state meters have

digital readouts, but the principles of operation can be better appreciated by

examining the older moving coil meters based on galvanometer sensors.

Figure 1.10: Ohmmeter Circuit Diagram

Voltmeter / Ammeter Measurements

The value of electrical resistance associated with a circuit element or

appliance can be determined by measuring the voltage across it with

a voltmeter and the current through it with an ammeter and then dividing the

measured voltage by the current (figure 1.11). This is an application of Ohm's

law, but this method works even for non-ohmic resistances where the

resistance might depend upon the current. At least in those cases it gives you

the effective resistance in ohms under that specific combination of voltage

and current.

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Figure 1.11: How to measure voltage and current

Voltage and Frequency Measurements

To measure voltage or frequency of a particular electrical signal, the

oscilloscope is setup to display a graph of voltage versus time. The signal to

be measured is applied to either the CH1 or the CH2 inputs. Triggering is set

to show a trace on the screen. Then the vertical (VOLTS/DIV) and horizontal

(SEC/DIV) scaling controls are adjusted to show the signal to be measured

appropriately on the screen. With all the knobs in their calibrated position, the

instantaneous voltage at any time can be read directly from the y-axis and the

period T (time for one cycle) can be read from the x-axis. Including

uncertainty) with the oscilloscope are made by reading the number of

divisions on the screen and multiplying by the scaling factor. The scaling

controls for uncertainty considerations are taken to be exact (as with most

measuring instruments, their calibrations are much more exact than the

reading of that instrument).

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Peak to peak voltage (actually measured trough to peak) is one type of

voltage measurement

Peak to Peak Amplitude = (5.2±0.1Div)(2V/Div) (Eq. 1.1)

= (5.2Div±2.0%)(2V/Div)

= (5.2Div)(2V/Div)±2.0%

= 10.40±0.20V

The period in this example was determined over two cycles for

increased accuracy. The greatest accuracy is attained by measuring

over the greatest part of the screen (same as in graphing where slope

is determined from points with the most separation).

Period = (8.0±0.1Div)(1ms/Div)/(2cycles) (Eq. 1.2)

= (8.0Div±1.3%)(1ms/Div)/(2cycles)

= (4.0ms)±1.3%

= 4.000±0.052ms

From the period, frequency is calculated;

Frequency = 1/Period (Eq. 1.3)

=1/(4.000±0.052ms)

=1/(4.000ms±1.3%)

=.25ms−1±1.3%

=0.2500±0.0033ms−1

=250.0±3.3Hz

(1Hz = 1 Cycle/sec)

Waveforms

A function generator is a very versatile instrument that is extensively

used in electronics, mechanics, bioengineering, physics and many other

fields. It allows you to create a wide variety of synthesized electrical signals

and waveforms for testing and diagnostic applications. Figure 1.12 shows the

most common functions such as the sine, square, triangle and ramp functions.

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Figure 1.12: Sample Waveforms

Each of the waveforms can be adjusted through the front panel

controls or remotely for frequency, amplitude and DC offset voltage. As an

example, let’s look at a sine function described by the following equation,

v(t)=VAsin(21ft) + VOFF (Eq. 1.4)

In which f is the frequency, VA the amplitude, and VOFF the offset voltage

as shown in Figure 1.13. Instead of amplitude one often used the RMS (Root

Mean Square) value to express the signal voltage level. For a sine wave the

RMS value is the amplitude divided by the square root of 2 or VRMS = VA/1.41.

The RMS is the most useful way to specify AC signal amplitudes.

4

Figure 1.13: Sine wave with amplitude VA , frequency f, and offset VOFF

Functions and Use of a Waveform Generator

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The function generator is based on digital signal processing (DSP)

methods. A DSP is basically a beefed-up microprocessor which is specially

designed for number crunching. DSPs are used in many everyday

instruments ranging from a compact disc player, an electronic synthesized

piano, or a voice-synthesized telephone answering message system. The

DSP is able to generate complex and arbitrary functions. The principle if fairly

simple and is called Direct Digital Synthesis. A simplified block diagram is

shown in Figure 1.14.

Figure 1.14: Block diagram of the waveform generator.

The heart of the instrument is a random-access-memory (RAM) which

stores the function (e.g. sine) in digital form. This memory is addressed

sequentially through an increment register. The frequency of the voltage

waveform is proportional to the speed with which the RAM is addressed. The

output data from the memory is a digital bit stream which is converted in the

actual (analog) wave shape through a Digital-to-Analog Converter (DAC). A

low pass filter at the output ensures a smooth waveform. The amplitude and

offset are controlled by changing the signal gain of the amplifier at the output

of the DAC.

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Any circuit can be represented by the Thevenin's equivalent circuit.

This is shown in Figure 1.15a. Vgen represents the waveform (sine, pulse, etc.)

and RT is the Thevenin resistance (output resistance).

Figure 1.15: (a) Thevenin's equivalent circuit; (b) Voltage divider

between the output and load resistors.

Important is that this output resistance of the function generator has a

value of 50 Ohm. This implies that the actual output voltage one measures

over the load will vary with the load resistance because of the voltage divider,

as shown in Figure 1.15b. The output amplitude is calibrated for a 50 Ohm

load resistance, which means that the voltage shown on the function

generator's display panel corresponds to the actual voltage VLOAD over the

load only when the load is equal to 50 Ohm. In other words, the value of

Vgen is double of the value displayed (or selected) by the function generator. If

the function generator's output is measured with no load connected (open

circuit or infinite resistance), the output voltage will be twice the displayed

amplitude. Thus, be careful when applying the output voltage of the function

generator to a circuit whose input resistance is different from 50 Ohm. In

general, it is a good practice to measure the amplitude of the waveform using

a Digital Multimeter (DMM) or an oscilloscope instead of relying on the

function generator display reading.

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Statement of the Problem

The main purpose of this project is to make sure that every trainer has

its own corresponding test equipment, to make things more convenient for the

students or trainees, and to make it easier to store and organize.

Specifically, the study aims to answer the following questions:

1. Designing, conceptualizing, and fabricating three (3) test

equipments, making it as a single equipment.

2. The effectiveness of the Portable Test Measurement is in contrast to

its individual equipments.

3. Some components for the Portable Test Measurement would be

from abroad.

4. The Portable Test Measurement is easy to repair.

Significance of the Study

The study is important because it is a need, a requirement and a

technology to look into. This will solve the worries of local schools in providing

quality hands-on education without fear of high cost test equipments. This

study is beneficial to the following:

School Administration – They will not have a hard time in keep track

of the equipments since the number of equipments are lessened and their

functionality the same.

Engineering Schools – The schools offering Bachelor of Science in

Electronics Engineering.

College Students – They are the beneficiaries of the equipments, and

their hands-on experience and knowledge will be enhanced.

Industries – They are the provider of jobs for Engineering Graduates.

With the result of this study they are assured that graduates from this

institution are well-rounded and prepared for the industry’s needs.

Future Researchers – They could probably add more features to the

PTM and use this study as basis.

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Scope and Limitations

Scope

This project includes imitation and fabrication of oscilloscope,

multimeter, and function generator using different components but of the

same function as the original ones.

Limitation

The specifications of the Portable Test Measurement are for laboratory

use only.

Multimeter

Voltmeter

o Maximum voltage measured = ±500 Vpeak

o Minimum voltage measured = 0v AC/DC

Ammeter

o Maximum current measured = 2000mA

o Minimum current measured = 0A

Ohmmeter

o Maximum resistance measured = 200 MΩ(ohms)

o Minimum resistance measured = 200 Ω(ohms)

Function Generator

Oscilloscope

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Definition of Terms

1. Alternating Current (AC) - an electric current that reverses its direction

many times a second at regular intervals, typically used in power supplies.

2. Direct Current (DC) - an electric current flowing in one direction only.

3. Frequency - is the number of occurrences of a repeating event per unit

time.

4. Resistance - is an electrical quantity that measures how the device or

material reduces the electric current flow through it. The resistance is

measured in units of ohms

5. Current - is a flow of electric charge. In electric circuits this charge is often

carried by moving electrons in a wire. It can also be carried by ions in an

electrolyte, or by both ions and electrons such as in plasma.

6. Voltage - is electric potential difference between two points of an electric

field.

7. Amperes - often shortened to amp, is the SI unit of electric current.

8. Period - the time between cycles of a periodic wave.

9. Amplitude - the maximum extent of a vibration or oscillation, measured

from the position of equilibrium.

10.Peak-to-peak amplitude - is the change between peak (highest amplitude

value) and trough (lowest amplitude value, which can be negative). With

appropriate circuitry, peak-to-peak amplitudes of electric oscillations can

be measured by meters or by viewing the waveform on an oscilloscope.

Peak-to-peak is a straightforward measurement on an oscilloscope, the

peaks of the waveform being easily identified and measured against the

graticule. This remains a common way of specifying amplitude, but

sometimes other measures of amplitude are more appropriate

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