CCT Tools & Equipment Operation 5 — Questions and Answers
Question 1: A calibration lab receives a flow meter that uses a turbine rotor. Which calibration method provides the most accurate volumetric flow reference?
- Comparison to a calibrated rotameter
- Gravimetric method using a weigh tank and timer (Correct answer)
- Differential pressure calculation from orifice plate readings
- Comparison to a variable area flow meter
Correct answer: Gravimetric method using a weigh tank and timer
The gravimetric method—collecting fluid into a weigh tank over a timed interval—provides a primary-level flow reference by directly measuring mass and time.
Question 2: When using a coordinate measuring machine (CMM) to calibrate a precision fixture, the stylus qualification step is performed to:
- Set the maximum probe contact force
- Determine the exact center and effective radius of the stylus ball (Correct answer)
- Clean the stylus tip before measurement
- Calibrate the machine's drive motors
Correct answer: Determine the exact center and effective radius of the stylus ball
Stylus qualification (probing a reference sphere) determines the stylus ball's effective center position and radius, which the CMM software uses to correct all subsequent measurements.
Question 3: A spectrum analyzer is used during RF power amplifier calibration. The instrument's resolution bandwidth (RBW) setting primarily affects:
- The frequency span that can be displayed
- The ability to resolve closely spaced signals and the noise floor (Correct answer)
- The maximum input power the analyzer can accept
- The sweep time calibration accuracy
Correct answer: The ability to resolve closely spaced signals and the noise floor
Narrower RBW improves frequency resolution between adjacent signals and lowers the displayed noise floor, while wider RBW speeds sweep time but reduces selectivity.
Question 4: Which technique is used to verify the linearity of a torque sensor over its full measurement range during calibration?
- Apply a single known torque at mid-range and extrapolate
- Apply certified torque at multiple ascending points and calculate deviation from best-fit line (Correct answer)
- Compare the sensor output to a reference sensor at full-scale only
- Zero the sensor and apply maximum rated torque three times
Correct answer: Apply certified torque at multiple ascending points and calculate deviation from best-fit line
Linearity is evaluated by applying known torques at multiple points across the range and comparing the actual output to the ideal straight-line response.
Question 5: A precision resistance standard is kept in a temperature-controlled oil bath during calibration. The primary reason for this practice is:
- To prevent mechanical vibration from affecting resistance
- To reduce the effect of temperature coefficient of resistance on the standard's value (Correct answer)
- To protect the standard from humidity-induced oxidation
- To allow electrical current to flow without contact resistance
Correct answer: To reduce the effect of temperature coefficient of resistance on the standard's value
Precision resistance standards have temperature coefficients that cause their resistance to change with temperature; oil bath control minimizes this variation during calibration.
Question 6: When calibrating a sound level meter, the calibrator is placed over the microphone and the meter reading is compared to the calibrator's certified output level. If the calibrator produces 94 dB SPL and the meter reads 93.4 dB, the meter has an error of:
- +0.6 dB
- -0.6 dB (Correct answer)
- +6%
- -6%
Correct answer: -0.6 dB
The meter reads 0.6 dB below the calibrator's true 94 dB output, so the meter error is -0.6 dB.
Question 7: Which statement correctly describes the difference between repeatability and reproducibility in the context of calibration equipment performance?
- Repeatability is measured over long time periods; reproducibility is measured in a single session
- Repeatability is variation under the same conditions by the same operator; reproducibility includes variation across operators, setups, or time (Correct answer)
- Repeatability applies to analog instruments; reproducibility applies to digital instruments
- Repeatability requires multiple instruments; reproducibility uses only one instrument
Correct answer: Repeatability is variation under the same conditions by the same operator; reproducibility includes variation across operators, setups, or time
Repeatability quantifies variation under fixed conditions (same operator, instrument, environment), while reproducibility captures variation when one or more of those conditions changes.
CCT Tools & Equipment Operation 5
A calibration lab receives a flow meter that uses a turbine rotor.
Which calibration method provides the most accurate volumetric flow reference?