CCT Tools & Equipment Operation 3 — Questions and Answers
Question 1: A calibration technician is using a gage block wringing technique. Which statement best describes proper wringing procedure?
- Slide and rotate gage blocks together with light overlapping pressure until they adhere (Correct answer)
- Press gage blocks firmly together with full face contact simultaneously
- Apply a thin layer of oil between blocks before pressing together
- Heat both blocks to the same temperature then press faces together
Correct answer: Slide and rotate gage blocks together with light overlapping pressure until they adhere
Proper wringing involves sliding and slightly rotating the blocks together so molecular adhesion and atmospheric pressure create a near-zero gap bond.
Question 2: Which type of pressure transducer output signal is most immune to electrical noise in long cable runs to a calibration data system?
- 0-5 VDC voltage output
- 4-20 mA current loop output (Correct answer)
- 0-10 VDC voltage output
- Frequency modulated output
Correct answer: 4-20 mA current loop output
A 4-20 mA current loop signal maintains constant current regardless of cable resistance, making it far more noise-immune than voltage signals over long runs.
Question 3: When verifying the accuracy of a calibrated pipette, which gravimetric standard is used to convert measured mass to volume?
- The density of mercury at 20°C
- The density of distilled water at the test temperature (Correct answer)
- The density of the liquid being dispensed
- The standard atmospheric pressure value
Correct answer: The density of distilled water at the test temperature
Gravimetric pipette calibration uses the known density of distilled water at the test temperature to convert the weighed dispensed mass to volume.
Question 4: A signal generator's frequency output is verified against a frequency counter traceable to a primary frequency standard. The generator reads 10.000 MHz but the counter shows 9.998 MHz. The generator error is:
- +200 Hz (0.002%)
- -200 Hz (-0.002%) (Correct answer)
- +2 kHz (0.02%)
- -2 kHz (-0.02%)
Correct answer: -200 Hz (-0.002%)
The generator outputs 9.998 MHz but indicates 10.000 MHz, so its actual output is 200 Hz low, giving an error of -200 Hz or -0.002%.
Question 5: For calibrating a hardness tester (Rockwell scale), which reference standard is applied?
- Certified hardness test blocks with known hardness values (Correct answer)
- A National Bureau of Standards weight set
- A calibrated force gauge at multiple load points
- A certified diamond indenter geometry certificate only
Correct answer: Certified hardness test blocks with known hardness values
Certified hardness reference blocks with traceable hardness values are used to verify and calibrate hardness tester performance at each scale.
Question 6: What is the primary purpose of using a low-thermal EMF shorting plug when zeroing a precision voltmeter?
- To prevent static discharge from affecting the measurement
- To eliminate thermoelectric voltage errors at the input terminals (Correct answer)
- To protect the meter input from overvoltage
- To provide a known reference voltage for offset adjustment
Correct answer: To eliminate thermoelectric voltage errors at the input terminals
Low-thermal EMF shorting plugs minimize thermoelectric (Seebeck effect) voltages at dissimilar metal junctions, which would otherwise add offset error to the zero reading.
Question 7: During calibration of an electronic balance, a standard weight is placed off-center on the pan. The purpose of this test is to evaluate:
- The balance's maximum capacity
- Corner load (off-center) error (Correct answer)
- Repeatability under load
- The sensitivity of the balance
Correct answer: Corner load (off-center) error
Off-center loading tests reveal corner load error, which occurs when the load cell or mechanism does not respond equally regardless of weight placement position.
CCT Tools & Equipment Operation 3
A calibration technician is using a gage block wringing technique.
Which statement best describes proper wringing procedure?