# Engineering Metrology Questions and Answers – Conditions of Comparison

This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Conditions of Comparison”.

1. What is TEI?
a) UNDE+NDE+TVE
b) UNDE-NDE-TVE
c) UNDE+NDE-TVE
d) UNDE-NDE+TVE

Explanation: NDE is a nominal differential expansion, UNDE is an uncertainty of nominal differential expansion, TVE is temperature variation error. NDE is the difference between the nominal expansion of master and part.

2. What is the maximum limit of TEI after which attention is required?
a) 5% of the tolerance part
b) 10% of the tolerance part
c) 15% of the tolerance part
d) 20% of the tolerance part

Explanation: If the TEI is > 10% of the part of tolerance, then attention is required. In close tolerance works, thermal effect is a single largest source of error. Efforts like applying correction and air conditioning doesn’t always solve the problem.

3. Which of the option is correct about given statements factors affecting standards?
Statement 1: A uniform temperature is important in metrology labs.
Statement 2: Ambient temperature may change by convection, conduction and radiation.
a) Only statement 1 is correct
b) Only statement 2 is correct
c) Both the statements are correct
d) Both the statements are false

Explanation: A uniform temperature is necessary because rate of thermal expansion is different for different materials. Ambient temp may change by convection, conduction and radiation but the effect of radiations is more troublesome.

4. Up to which length of gauges, there is no appreciable change in length with a method of support?
a) 75 mm
b) 100 mm
c) 150 mm
d) 200 mm

Explanation: For small gauges upto 75 mm length, there is no appreciable change in length for a method of supports. But dimensions of long gauges may change even by their own weight.

5. What is the full form of TEI?
a) Total error index
b) Total expansion index
c) Thermal expansion instrument
d) Thermal error index

Explanation: Thermal error index can be reduced by establishing a more accurate coefficient of expansion, making corrections for NDE, minimizing temperature variation from 20 degree C.

6. What is the value of humidity in test laboratories for performing a measurement or any other operation?
a) 35±10%
b) 45±10%
c) 55±10%
d) 65±10%

Explanation: Lower RH value can invalidate measurement by building static charge. High value of RH can cause leakage. It should be maintained at 45±10%.

7. Which of the following statement is correct for given statements?
Statement 1: Nitra-alloy is an ultrastable material.
Statement 2: In steel coefficient of expansion can be increased by adding nickel.
a) F, F
b) F, T
c) T, T
d) T, F

Explanation: Metallurgic compositions also affect the stability of the material. Coefficient of expansion of steel can be reduced by adding nickel. It is desirable to have materials with the same coefficient of expansion.

8. Which of the following statement is not suitable to reduce error produced by temperature variation?
a) Increase rate of air flow
b) Increase the frequency of variation of temperature
c) Increase the amplitude of temperature variation
d) Redesign masters and comparators

Explanation: Decrease in an amplitude of temperature variation is a factor to reduce error produced by temp variations. Redesigning of masters and comparators may reduce this error by balancing time cons. and coefficient of expansion with part to be measured.

9. Which of the following option is correct for given statements about factors affecting accuracy in metrology?
Statement 1: Acoustic noise should be restricted below 45-60 dB.
Statement 2: Humidity corrodes non-ferrous materials only.
a) Only statement 1 is true
b) Both the statements are true
c) Only statement 2 is true
d) Both the statements are not true

Explanation: There is an effect of acoustic noise on sensitive measurement, it value should be less than 45-60 db. Humidity should be maintained at a constant value, it can corrode ferrous materials.

10. Which of the following option is not suitable for environmental conditions in labs?
a) Wet dust particles decrease insulation resistance
b) Dry dust increase surface resistivity
c) A negative air pressure should be maintained in labs
d) Electrostatic precipitators used to collect dust particles

Explanation: A positive air pressure of about 10 to 20 N/m2 relative to outside area is recommended in labs. Electrostatic precipitators are used to collect and attract dust particles, for this purpose they can be placed in corners.

Sanfoundry Global Education & Learning Series – Engineering Metrology.

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