CET Data Quality & Completeness 3 — Questions and Answers
Question 1: A technician evaluates a sensor's ability to detect the smallest meaningful change in the measured variable. This specification is called:
- Accuracy
- Resolution (Correct answer)
- Hysteresis
- Repeatability
Correct answer: Resolution
Resolution is the smallest change in the measured quantity that produces a detectable change in the instrument's output.
Question 2: In digital communications, a CRC-16 generates a remainder of 0 upon checking received data. This indicates:
- The data has a single-bit error
- No errors were detected in the received data (Correct answer)
- The transmission speed was too high
- The CRC polynomial is incorrect
Correct answer: No errors were detected in the received data
A remainder of zero after CRC division means no errors were detected; however, CRC cannot guarantee absolute error-free data for all error patterns.
Question 3: Which term describes the closeness of agreement among repeated measurements of the same quantity under identical conditions?
- Accuracy
- Trueness
- Precision (Correct answer)
- Linearity
Correct answer: Precision
Precision (or repeatability) refers to how closely repeated measurements agree with each other, independent of how close they are to the true value.
Question 4: An electronics technician finds that an oscilloscope probe has a 10:1 attenuation ratio. If the displayed voltage is 3.5 V, the actual circuit voltage is:
- 0.35 V
- 3.5 V
- 35 V (Correct answer)
- 350 V
Correct answer: 35 V
A 10:1 probe attenuates the signal by a factor of 10, so the actual voltage is the displayed value multiplied by 10 (3.5 × 10 = 35 V).
Question 5: What is the primary purpose of using a guard ring in a high-precision measurement circuit?
- To provide a low-impedance ground path for high-frequency signals
- To reduce leakage currents that would corrupt high-resistance measurements (Correct answer)
- To shield the circuit from electromagnetic interference
- To improve the thermal stability of precision resistors
Correct answer: To reduce leakage currents that would corrupt high-resistance measurements
Guard rings intercept leakage currents from high-impedance nodes and return them to a driven guard voltage, preventing them from corrupting sensitive measurements.
Question 6: In data acquisition, which technique involves taking multiple samples and averaging them to improve effective resolution?
- Dithering
- Oversampling and decimation (Correct answer)
- Sample-and-hold
- Anti-aliasing
Correct answer: Oversampling and decimation
Oversampling followed by digital filtering and decimation can increase the effective number of bits (ENOB) beyond the ADC's native resolution.
Question 7: A spectrum analyzer measurement shows a spurious signal 60 dBc below the fundamental. What does 'dBc' indicate?
- Decibels relative to a 1-milliwatt reference
- Decibels relative to the carrier or fundamental signal (Correct answer)
- Decibels of cable loss at the measurement point
- Decibels of common-mode rejection
Correct answer: Decibels relative to the carrier or fundamental signal
dBc (decibels relative to carrier) expresses the power of a signal relative to the fundamental or carrier signal power.
CET Data Quality & Completeness 3
A technician evaluates a sensor's ability to detect the smallest meaningful change in the measured variable.
This specification is called: