CMO Equipment Calibration & Diagnostics 5 — Questions and Answers
Question 1: Which calibration interval strategy is based on analyzing historical out-of-tolerance rates to optimize the frequency of calibration?
- Fixed-time interval
- Risk-based calibration interval optimization (RBCI) (Correct answer)
- Manufacturer-default scheduling
- On-demand calibration
Correct answer: Risk-based calibration interval optimization (RBCI)
Risk-based calibration interval optimization uses historical as-found data and failure analysis to adjust intervals — tightening them for unstable instruments and extending them for consistently in-tolerance ones.
Question 2: A Mobilyze operator observes that a sensor's output noise level has increased significantly. Which diagnostic step should be performed first?
- Replace the sensor immediately
- Check power supply voltage stability and grounding integrity (Correct answer)
- Re-calibrate at double the usual points
- Increase the signal filter gain in the ECU
Correct answer: Check power supply voltage stability and grounding integrity
Increased noise often originates from unstable power supply voltage or poor grounding before the sensor itself fails, making electrical checks the logical first step.
Question 3: What is 'measurement uncertainty' in a calibration context?
- The probability that the calibration was performed incorrectly
- A quantified range within which the true value of the measured quantity is believed to lie (Correct answer)
- The difference between two successive calibration results
- The maximum load the reference standard can handle
Correct answer: A quantified range within which the true value of the measured quantity is believed to lie
Measurement uncertainty is a statistical parameter that expresses the dispersion of values that could reasonably be attributed to the measurand.
Question 4: During a Mobilyze hydraulic system diagnostic, pump output pressure is normal but actuator extension speed is below specification. The most likely cause is:
- Pump calibration error
- Internal actuator seal leakage bypassing fluid (Correct answer)
- Load cell offset error
- ECU sensor input clamp
Correct answer: Internal actuator seal leakage bypassing fluid
When pump pressure is correct but actuator speed is slow, fluid is bypassing the actuator piston internally through worn or damaged seals rather than doing useful work.
Question 5: What is the purpose of an 'as-left' record in calibration documentation?
- To record the condition of the instrument after any adjustments have been made (Correct answer)
- To log the technician's departure time from the site
- To document the pre-calibration environmental conditions
- To list the tools used during the calibration procedure
Correct answer: To record the condition of the instrument after any adjustments have been made
The as-left record captures the instrument's final calibrated state after any adjustments, confirming it meets tolerance before being returned to service.
Question 6: A Mobilyze operator notices a fault code indicating 'LVDT excitation failure.' What does this mean?
- The linear variable differential transformer is not receiving its required AC supply voltage (Correct answer)
- The LVDT core has been displaced beyond its linear range
- The LVDT output has exceeded its rated millivolt range
- The LVDT calibration file has become corrupted
Correct answer: The linear variable differential transformer is not receiving its required AC supply voltage
An LVDT requires an AC excitation voltage to operate; an excitation failure means this supply is absent or out of specification, rendering the sensor inoperable.
Question 7: Which practice ensures calibration results remain valid when a reference standard is sent out for external calibration?
- Estimating corrections based on previous calibration results
- Using a secondary transfer standard to maintain traceability until the primary standard returns (Correct answer)
- Suspending all calibration activity until the standard is returned
- Replacing the standard with a general-purpose digital meter
Correct answer: Using a secondary transfer standard to maintain traceability until the primary standard returns
A secondary (transfer) standard, itself traceable and in calibration, bridges the gap so calibration work can continue with documented traceability.
CMO Equipment Calibration & Diagnostics 5
Which calibration interval strategy is based on analyzing historical out-of-tolerance rates to optimize the frequency of calibration?