This document discusses various types of measurement standards used to define units of length. It describes line standards such as the meter which is defined based on the wavelength of light, and end standards like slip gauges which provide precise length measurements. The document also covers calibration, which is the process of comparing instruments to known standards to determine accuracy and adjust measurements. A variety of linear measurement tools are discussed, including vernier calipers, micrometers, height gauges, and digital instruments used to precisely measure internal and external dimensions.

1. Measurement
Standards

2. “Precisionis a Religion& Measurement
Standards make it happen”(ArunKudale)
• History of Measurement Standards:

3. Standards
• Definition:
• The word Standard means something that is set up & established
by authorities as a rule for the measurements of quantity, weight,
value etc.
• Types of Standards:
1. Line Standard
2. End Standard
3. Wavelength Standard

4. • Line Standard:
• According to line Standard the yard or meter is defined as the
distance b/w inscribed lines on a bar of metal under certain
condition of temperature % support.
• This is legally authorized & an act of parliament.
a) The imperial Standard Yard:
• The yard is defined as the distance b/w central transverse line on
the plugs.
• When the temperature is constantly at 62F & the bar is supported
on rollers.
• As shown in Figure:

6. a) International standard Prototype meter:
• The international bureau of weights & measurements establish
meter as Linear measuring standard in 1875.
• It is the distance b/w the center portion of two lines engraved on
the polished surface of a bar.
• That is made of Platinum-iridium alloy having a unique (web)
cross section as shown:
• Meter is also defined as the path traveled by light in a vacuum
during a time interval of 1/299792458 of a second.
• The examples of line standard includes meter, Yard, steel Rule
(Scale) etc.

8. • End Standard:
• The need of line standard arises as the use of line standard was
difficult at various places in workshops.
• End standards can be made to a high degree of accuracy.
a) End Bar:
• It is made of steel having cylindrical cross sections.

9. End Bar

10. • Slip Gauges:
• They are practical end standards and can be used in linear
measurement in many ways.
• Theses were invented by a Swedish engineer C E Johnson.
• Slip gauge sets are made according to the following conditions:
IS 2984-1981, Metric BS-4311: 1968
Imperial BS.888.1950, DIN: 861-1988
JIS B 7506-1978

12. Types of Slip Gauges

13. • Wavelength Standard:
• High sensitivity length measurements are very important as
theses are widely used & they are of type that have highest
accuracy after time frequency measurements.

14. Subdivision of Standards
1. Primary Standards
2. Secondary Standards
3. Tertiary Standards
4. Working Standards
• Reference Standards
• Calibration Standards

15. Calibration
• It is a comparison of Instrument performance to standards of
Known accuracy.
• Calibrations directly link customers measurement equipment
to national & international standards.
• According to ISO, Calibration is the quantitative determination
of errors of measuring instruments & adjusting them to a
minimum.
• In other words, calibration means to find out whether the
instrument gives correct reading or not.
• It also includes minor adjustments to the instrument.

16. • Calibration Labs are to be set at the
following different levels:
a. In-house Calibration Lab
b. Professional Calibration Labs
c. National Accreditation board for testing
(NABL) Certification to professional Labs

17. Status of Calibration
1. Active
2. Calibration Before Use (CBU)
3. Only for indication (OFI)
4. Rework
5. Reject
6. Write-off

18. Standard Procedure for Calibration
1. Cleaning of Instrument
2. Determination of Error
3. Check for Tolerable Limit
4. Minor Changes
5. Allotment of Calibration Set up
6. Next Calibration date

20. Assignments
• Case Study:
1. Dial calibration Tester
2. Calibration of Gauge block measuring Unit

21. Linear Metrology

22. Linear Metrology
• It is defined as the science of linear measurement, for the
determination of the distance b/w two points.
• It is applicable to all external and internal measurements i.e.
distance, length, diameter, thickness, straightness etc.
• Its principle is to compare the dimension to be measured &
aligned with standard dimensions marked on the measuring
instrument.

23. • Linear Metrology follows the following two approaches:
1. Two-Point Measuring-Contact-Member Approach
• Vernier Calipers, Micrometer for Measuring Distance
2. Three-Point Measuring-Contact-Member Approach
• Out of three measuring contact members, two are fixed
• E.g. to measure the diameter of a block held in V block
• The Instruments used in Linear Metrology are Classified as:
1. Non Precision Measuring instruments e.g. Steel Rule
2. Precision Measuring Instruments e.g. Vernier Calipers

24. STEEL RULE (Scale)
• It is the Simplest & most Commonly used linear Measuring
instrument.
• It measures an unknown Length by comparing it with the one
previously Calibrated.
• It is used to measure components of lower accuracy.
• The Figure Shows different Steel Rules (scales)

25. CALIPERS
• A caliper is used to measure the distance b/w two points.
• It use a precise slide movement for inside, outside, depth or
step measurement.
• It consist of two legs hinged at the top, wit the ends of the
legs spanning the part to be measured.
• Calipers should be held gently near the joint & square to the
work by applying light gauging pressure to avoid disturbance
during setting for accurate measurement.

26. Types of Calipers
1. Inside Calipers:
• It has Made with straight legs which are bends outwards.
• Used for measuring inside diameter.
• Opening can be checked by rule or micrometer.
2. Outside Calipers:
• It has two legs which are bends inwards.
• Mainly used for measuring outside calipers.
3. Spring Calipers:
• It is the improved variety of ordinary
friction-joint caliper.
• the two leg carry a curved spring at the top
fitted in notches used to force the spring apart.

28. 4. Center Measuring Calipers
• It has conically pointed jaws designed to measure the distance b/w
center of the holes.
5. Gear Tooth Calipers:
• It has adjustable tongue designed to measure the thickness of gear
teeth at the pitch line.
6. Machine Travel Calipers:
• It is designed to measure the position change of a machine.
7. Rolling mill Calipers:
• It is a simple device used for quick gauging of a stock in production
Environment.
8. Sliding Calipers:
• It use a precise slide movement for inside, outside, depth or step
measurements.

29. Vernire Caliper

31. Example
Main scale reading =35mm
The vernier division coinciding with the main scale is the 20th division.
Value=20 multiplied by 0.02=0.40mm.
Total reading is 35mm+0.40= 35.40mm
35.40 mm

32. VERNIER HEIGHT GAUGE
The main parts of a vernier height
gauge and their function are given.
1.base
2. beam
3.vernier slide
4. fine setting device
5. vernier plate
6. locking screws
7. scriber

33. VERNIER DEPTH GAUGE
 Base
 Graduated beam
 Clamping screw
 Fine adjustment
mechanism
 Vernier scale

34. Digital Vernier Caliper

35. Micrometer

36. • A micro meter is a precision instrument used to measure a job,
generally within an accuracy of 0.01mm.Micrometer used to take
the outside measurements are know as outside micrometer.
Least Count =
𝑆𝑚𝑎𝑙𝑙𝑒𝑠𝑡 𝐷𝑖𝑣𝑖𝑠𝑖𝑜𝑛 𝑜𝑛 𝑚𝑎𝑖𝑛 𝑆𝑐𝑎𝑙𝑒
𝑇𝑜𝑡𝑎𝑙 𝑛𝑜.𝑜𝑓 𝑑𝑖𝑣𝑖𝑠𝑖𝑜𝑛𝑠 𝑜𝑛 𝑐𝑖𝑟𝑐𝑢𝑙𝑎𝑟 𝑠𝑐𝑎𝑙𝑒
• Micrometers are classified into following types:
1. Outside Micrometers
2. Inside Micrometers
3. Depth gauge Micrometers

39. Digital measuring Instrument for
Internal & External Dimensions