Calibration Flashcards
7 cards from real CPE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Calibration flashcards as text
When calibrating a computerized polygraph (CPST), the examiner confirms the analog-to-digital (A/D) conversion sampling rate. A minimum adequate sampling rate for polygraph physiological signals is approximately:
Answer: 60 samples per second
Polygraph physiological signals (0.05–20 Hz range) require at least twice the highest frequency of interest; 60 samples/second is a practical minimum for accurate reproduction.
An examiner notices that the electrodermal tracing recovers to baseline but then dips below the original baseline level. This phenomenon is called:
Answer: The negative rebound or undershoot
Post-response undershoot occurs when sweat gland activity falls below basal levels during recovery, reflecting a temporary rebound in sympathetic inhibition.
During calibration, the examiner tests the respiration sensor by asking the subject to take a deep breath. The expected tracing response is:
Answer: A smooth upward deflection during inhalation and downward during exhalation
A properly calibrated pneumograph shows a smooth upward deflection during inhalation and a downward return during exhalation, confirming correct sensor response.
A polygraph examiner is calibrating two different instruments to use in a comparison study. To ensure comparability, the examiner must verify that both instruments have:
Answer: Equivalent frequency response and sensitivity settings
Comparable frequency response and sensitivity settings ensure that physiological signals are measured and displayed equivalently across both instruments.
What is the function of a 'centering' or 'balancing' control on a polygraph amplifier?
Answer: To position the tracing in the center of the recording channel without changing gain
The centering control shifts the DC offset of the tracing to place it visually in the middle of its channel, independent of the amplification level.
Why should polygraph electrodes used for electrodermal measurement be checked for corrosion before calibration?
Answer: Corroded electrodes can introduce unstable contact resistance, degrading signal quality
Corrosion on electrode surfaces introduces variable and unstable contact impedance, introducing noise and making electrodermal measurements unreliable.
During calibration, the examiner observes that the pneumograph tracing shows a characteristic 'staircase' or stepped appearance rather than smooth curves. This artifact most likely results from:
Answer: A digitization or quantization error in a computerized system with insufficient resolution
A staircase artifact in digital systems indicates insufficient bit-depth (quantization resolution), causing smooth analog waveforms to appear as discrete steps.