CMO Equipment Calibration & Diagnostics 3 — Questions and Answers
Question 1: A Mobilyze operator is calibrating a temperature sensor and finds the output is accurate at 32°F but reads 4°F low at 212°F. This error is best described as:
- Offset error
- Gain (span) error (Correct answer)
- Quantization error
- Reference junction error
Correct answer: Gain (span) error
When the error increases proportionally with the measured value rather than remaining constant, it indicates a gain or span error in the sensor.
Question 2: What is the recommended minimum ratio of reference instrument accuracy to the instrument under test during calibration?
- 1:1
- 2:1
- 4:1 (Correct answer)
- 10:1
Correct answer: 4:1
The 4:1 accuracy ratio (also called the test uncertainty ratio) ensures the reference standard contributes minimal uncertainty to the calibration result.
Question 3: During a diagnostic cycle, the Mobilyze control unit displays an intermittent CAN bus communication error. The most likely cause is:
- A miscalibrated load sensor
- Loose or corroded connector on the CAN bus network (Correct answer)
- Incorrect span setting in the ECU
- Overloaded hydraulic circuit
Correct answer: Loose or corroded connector on the CAN bus network
CAN bus communication errors are most commonly caused by physical layer issues such as loose connections, corrosion, or damaged wiring rather than calibration problems.
Question 4: After replacing a Mobilyze proximity sensor, the operator must perform which procedure before returning the equipment to service?
- Oil change and filter replacement
- Functional calibration verification using a known reference position (Correct answer)
- Full hydraulic pressure test
- Engine idle speed adjustment
Correct answer: Functional calibration verification using a known reference position
Any sensor replacement requires a functional calibration check against a known reference to confirm the new sensor is correctly sensing position.
Question 5: Which diagnostic parameter indicates that a Mobilyze actuator is consuming more current than specified at a given load?
- Low supply voltage
- High insulation resistance
- Current draw above rated amperage (Correct answer)
- Excessive back-EMF
Correct answer: Current draw above rated amperage
Current draw exceeding the rated amperage at a specified load typically indicates internal friction, mechanical binding, or motor degradation.
Question 6: The purpose of a 'dead-weight tester' in pressure calibration is to:
- Simulate maximum hydraulic load on the system
- Provide a highly accurate reference pressure using known masses and piston area (Correct answer)
- Test seal integrity under static conditions
- Measure fluid viscosity at operating temperature
Correct answer: Provide a highly accurate reference pressure using known masses and piston area
A dead-weight tester uses calibrated masses on a known piston area (P = F/A) to generate precise, traceable reference pressures for calibrating gauges and transducers.
Question 7: When documenting a calibration event for a Mobilyze instrument, which information is NOT typically required in the calibration record?
- As-found and as-left readings
- Operator's daily mileage log (Correct answer)
- Reference standard used and its calibration certificate number
- Environmental conditions (temperature, humidity)
Correct answer: Operator's daily mileage log
The operator's mileage log is unrelated to calibration records; required data includes as-found/as-left readings, reference standards, and environmental conditions.
CMO Equipment Calibration & Diagnostics 3
A Mobilyze operator is calibrating a temperature sensor and finds the output is accurate at 32°F but reads 4°F low at 212°F.
This error is best described as: