1

CALIPERS

CALIBRATION By:Mukesh Jeswani

2

Table Of ContentSr No Details Page #

01 Purpose 03

02 Scope 04

03 Procedure 05

04 Environment Condition 06

05 Preliminary instructions 08

06 Reference 09

07 Measurement Standard 10

08 Types of Standards 11

09 Specifications 17

10 Detailed Procedure 18

11 Out lie of Calibration Procedure 28

12 Calibration Report 29

13 Accuracy Table 32

14 Calibration Log 34

15 Traceability – Metutoyo Calipers 36

3

PURPOSE

• Provide general instruction for calibration of calipers• Types of calipers1. Vernier2. Dial3. Digital

4

Scope

• All calipers used to measure ,gage,test,inspect and control part compliance to customer specifications and drawings.

• Principle measuring surfaces of calipers should be calibrated.

5

Procedure

• Priliminary Instructions and notes.1. Calibration shall be performed in an environment

condition specified by manufactures manuals• Impact of environment like temperature, humidity,

radio frequency ,vibration and dust control to make accurate measurement for calibration of calipers

• As per ISO/IEC17025 laboratory shall monitor,cotrol and record environmental condition at the time of calibration

6

Environment Condition

• Following things to remember for maintaining a laboratory environment.

1. 45 % relative humidity is maximum for dimensional areas to prevent rust

2. 20% minimum for preventing equipment from static discharge3. Temp must be measured at work surface height4. Temp must be measured at several point at working surface

height.5. Air pressure should be heigher then surrounding area to reduce

dust6. Temp. must be 20 ± 0.3°C and humidity 20 to 45 % in

calibration laboratory

7

Environment Condition

7.The temp. control necessary depends on item which to be calibrated and uncertainties required .

8.For controlled temperature for item which calibrated may allow to soak in liquied.Temperature difference between equipment,standareds and the item being measured are as small as possible.

8

Priliminary instructions

2 The caliper will hereafter be referred to as the instrument under test (IUT)

3 Verify that IUT is clean and visually examine .4 Refer to manufacture manual if any of the requirement

cannot be meet for calibration of calipers.5 If defect observed while calibration continue then

discontinue calibration and necessary corrective action should be taken.

6 Use extreme care when removing dirt, fingerprints and other foreign substances so that cleaning solutions do not enter internal portions of the IUT

9

Reference

• Manufacturers Manual• Its defined as materials whose property value are

sufficiently homogenous and well established to be used for calibration of apparatus and assessment of measurement method.

• Materials whose property value are traceable to procedure that establishes traceability to accurate realization of the unit in which property values are expressed. It is called certified reference material

10

Measurement Standard

• It is defined as a materials measure measuring instrument ,reference materials or measuring system intended to define ,realize, conserve or reproduce a unit of one or more values of a quantity to serve as a reference.

11

Types Of Standards

1. International• It recognized by international agreement to serve

internationally as the basis for fixing the value of all other standard

• Example : Prototype of kilogram maintain at the international Bureau of weight and Measures( BIPM) is an international standard for Mass

12

Types Of Standards

2 . National• A standard recognized by an official national

decision to serve in a country as the basis for fixing the value of all other standards of quantity concerned. It is primary standard to which others standard are traceable.

• Example: Identical prototype of national kilogram to prototype with international prototype, are maintain national standard of mass in various NMIs

13

Types Of Standards

3. Primary• Having highest metrological quality.• Values accepted without reference to other standard

of the same quality.• National standard are generally primary standard.

14

Types Of Standards

4. Secondary• Standard whose value is based on comparison with

some primary standard.• Once its value establish then it become primary

standard for other users.5. Reference• Having highest metrological quality available at

given location from which the measurement made at that location are derived.

15

Types Of Standards

6. Working: A measurement standard not specifically reserved as

a reference standard which is intended to verify measuring equipment of lower accuracy.

7. TransferStandard same as reference standard except that it is used to transfer a measurement parameter from one organization to another for traceability purposes.

16

Example of Standard(DIN)

17

Specifications

• Its determined by calipers manufacturer’s documentation.• Standards listed below should be selected on the basis of

their higher accuracy level when compared to the unit under test.

• Equivalent Standards must be equal to or better than the minimum –use-specification.

• Minimum-Use-Specification for standards listed are ¼ the accuracy required by the IUT

1. Cleaning solution2. Hard arkansas stone3. Lint free cloth 4. Gage block set5. Fine wire or nylon brush6. Guage oil

18

Detailed Procedure

1. Carefully examine all gauging surfaces for nicks,burrs,sratches,wear or other signs of mishandling that may affect accuracy of the instrument.Remove any positive imperfections utilizing a hard arkansas stone.

2. Apply sufficient amounts of cleaning solution to dampen a lint free cloth. Carefully clean all exposed surfaces removing all foreign material and particulate matter by using brush on pinion track if neccessary.lightly apply gauge oil to clean surfaces.

19

Detailed Procedure(Conti..)

3. Check O.D jaws when in the closed position. Hold calipers to light source and visually examine for light between the jaws.Light will not be seen if jaws are parallel.

4. Check I.D. Knife –edge jaws for wear when in the close position.Caliper must be positioned squarely in line of sight to detect air gaps or surface imperfections between jaws.

20

Detailed Procedure(Conti..)

5. Verify zero setting of caliper by observing the indicated reading with jaws in the closed position.If calipers does not read 0.000,Dial caliper can be easily adjusted to zero by loosening the bezel lock screw ,then rotating bezel to align the zero graduation to the pointer.

6. Check depth measuring feature using gage block.Note dial reading when checked at zero and at the measured value of the gage block.

21

Detailed Procedure(Conti..)

7.Check depth measuring feature using gage block.Note reading when checked at zero and at the measured value of the gage block.

8. If any defects have been found at this point that would affect accuracy or function of the gage,discontinue calibration and refer for remedial action.

9. Check four quadrants equally spaced throughout the entire measurement range of the caliper e.g 1.000”,3.000”,4.000”,6.000”

22

Detailed Procedure(Conti..)

10.Align the beam of the caliper to be as nearly parallel to

the line of measurement as possible.11.Tighten clamp screw on the movable jaw without

disturbing “feel” between the caliper and gage block to ensure precision measurement.The clamp screw must be tightened due to the “play” within the sliding member on the movable jaw.

12.Read caliper without disturbing placement. If not carefully remove caliper to obtain reading.

23

Detailed Procedure(Conti..)13.Repeat the measurement steps a sufficient number of

times to rule out any obviously incorrect reading.14. Record all above reading on the Equipment Calibration Record.15.Label each instrument with calibration date,

due date and person performing calibration.

24

Calibration Interval

• Calibration interval depend on how often used of calipers ,types of environment and to what extent the user expects it to repeat measurement

• Company is monitoring how often each calibration performed met or did not meet specification by

which it give pass result and fail result as per specification.

• Pass rate = number of times passed calibration – number of time failed calibration/total number of calibration

25

Detailed Procedure(Conti..)

• If pass rate varied between 98 to 100 % then interval were double ,95 to 98 % then interval were increased by 50% and for below 95 % then interval should be reduce or monitored for another round of calibration.

• Calibration interval analysis methods are categorized by their effectiveness ,cost to implement , their suitability for large and small inventories and others factors.

• Two group for analysis of calibration interval1. Use statistical test 2. without statistical test

26

Detailed Procedure• Next due date calculate by date, month and years

from day the equipment was last calibrated . Others used only month and year.

• More flexible when used only day and month by doing calibration when production shutdown for maintenance and repair used for calibration of equipment.

• In day/month/years system exact interval is applied to each calipers equipment.

27

Detailed Procedure

• Subset of interval analysis is Delay Dating• It is a practice of lengthening the calibration interval

by amount of time after calibration that equipment is not in use and kept in storage under controlled condition.

• Benefit for saving time and money

28

Out Line Of Calibration Procedure

PROCEDURE:• Place the standard Lengths of 25 mm between the measuring jaws of the

caliper at three different positions and determine the length.• Determine the average length and record the observations.• Repeat the above procedure for the remaining standard lengths (50 mm, 75

mm, 100 mm and 125mm).• Tolerance: + 0.05 mm• Frequency: Once in a month• Maintenance & repairs:• When the instrument does not comply with the requirement specified

above; the instrument should be labelled as “Out of Calibration” and should get repaired / serviced.

• After repairing / servicing the instrument before taking for use, the instrument must be calibrated as per the above-mentioned procedure.

29

Calibration Report QUALITY ASSURANCE DEPARTMENT

CALIBRATION REPORT OF VERNIER CALIPER Reference – Date - Frequency - Once in a Month Instrument No. - Make –

Place the standard length between measuring jaws of the caliper at three different positions and determine the length.

Sr. No.

Standard Length Rods (mm)

Reading of Measuring Jaws at Position (mm)

Average Reading

(mm)

Limit (mm)

Upper Center Lower Min. Max.

1 25 24.95 25.05 2 50 49.95 50.05 3 75 74.95 75.05 4 100 99.95 100.05 5 125 124.95 125.05 Conclusion: Calibration is satisfactory / not satisfactory. Next Calibration Due On : Done By : Date :

Checked By : Date :

30

Labeling

Hint for manage labels:I. use black or dark ink ( No pencil, crayons)II. Cover the label with tape to help preserve the data III. Make a new label if an error is made( white-out and

line-out are not acceptable)IV. Never use technician’s stamp , name or identifying

mark in yr workV. Keep all labels in a secure , locked area, with access

limited onlyVI. Used alternate for small specimen like metal tag,

color coding ,or manila tag

31

Calibration labels

32

Accuracy Table

Measuring Product Identification Product Dimensions Measuring Tool Ordered Tightest Measuring Equipment Accuracy

Tool Characteristics / Serial# Description Range Range Tolerance Resolution level

Tape Width L516CME Lufkin 16' / 5m 1/16" - 144" 1/16" - 192" +/- 1/32" 1/32" 1:1

measure & length

Steel ruler width No. R590 - 18 WESTCOTT 1/16" - 18" 1/16" - 18" +/-0.02" 1/16" 1: 1.5

& length 18" Stainless Steel ruler

with hang up hole

ACCURACY TABLE - LABORATORY EQUIPMENT

33

Accuracy Table Of different Calipers used at company

Accuracy Table of diffent Calipers uesd at Company:

Inch/Metric

Part # Range Accuracy LCD Resolution Remarks0-6in .0005in

0-150mm 0.01mm0-6in .0005in

0-150mm 0.01mm0-8in .0005in

0-200mm 0.01mm0-8in .0005in

0-200mm 0.01mm0-12in .0005in

0-300mm 0.01mm0-12in .0005in

0-300mm 0.01mm0-12in .0005in

0-300mm 0.01mm0-12in .0005in

0-300mm 0.01mm0-4in .0005in

0-100mm 0.01mm0-6in .0005in

0-150mm 0.01mm0-8in .0005in

500-172-20 ±.001in -

500-170-20 ±.001in .075" Round depth bar

500-171-20 ±.001in -

500-167 ±.0015in Carbide-tipped jaws for OD measurement

500-168 ±.0015in Carbide-tipped jaws for OD and ID measurement

500-165* ±.0015in Carbide-tipped jaws for OD measurement

500-166* ±.0015in Carbide-tipped jaws for OD and ID measurement

500-163-20* ±.001in Carbide-tipped jaws for OD measurement

500-164-20* ±.001in Carbide OD/ID Jaws

500-159-20* ±.001in Carbide-tipped jaws for OD measurement

500-160-20* ±.001in Carbide-tipped jaws for OD and ID measurement

34

Calibration Log

QA EQUIPMENT CALIBRATION LOGCurrent date 20-Jun-13

Item

Equipment Description

Identification / Serial # Location

Calibration Frequency

YR 2006 Date

Calibrated by

YR 2007 Date

Calibrated by

YR 2008 Date

Calibrated by

YR 2009 Date

Calibrated by

YR 2010 Date

Calibrated by Due date

Gram Scale Weight

ACCULAB Vicon

Serial# 19356069

QA Lab -tabel Annually Nov/3/06

Calibrated by Interweigh Systems Inc. 4-Dec-07

Interweigh Systems Inc. 16-Mar-09

Interweigh Systems Inc. 6-Mar-09

Interweigh Systems Inc. 18-Mar-10

Interweigh Systems Inc. 18-Mar-11

Digital force gauge

Mar-10 Corp

Model# MG50 SN# 59908 Annually 18-Mar-10 In-House 18-Mar-11

Production Weight Scales

Gram Weight Scale

Scout Pro- SP 202

Serial # 7123262112 Lost Annually

Oct/27/06

Calibrated by Interweigh Systems Inc. Lost

Mettler Toledo Weight Scale

Scale #1- PTHK

Serial # 0016008-6DF Reclaim Annually

Oct/27/06

Calibrated by Interweigh Systems Inc. 4-Dec-07

Interweigh Systems Inc. 3-Jun-08

Interweigh Systems Inc 1-Jun-09

Interweigh Systems Inc ########

Interweigh Systems Inc 18-Mar-11

35

36

Traceability – Metutoyo Calipers