CCT Electrical & Electronic Calibration Flashcards
6 cards from real CCT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CCT Electrical & Electronic Calibration flashcards as text
What is the primary use of a Josephson junction array in electrical metrology?
Answer: Realizing the SI unit of voltage with quantum-level accuracy
A Josephson junction array provides a quantum-based, highly accurate realization of the volt, serving as the primary voltage standard at national metrology institutes like NIST.
When calibrating an insulation resistance tester (megohmmeter), what type of reference standard is used?
Answer: A precision resistor with a known high-resistance value
High-value precision resistors with known, stable resistance values (often in the megaohm to gigaohm range) are used as reference standards when calibrating megohmmeters.
What effect does temperature have on precision resistors used as calibration standards?
Answer: Temperature causes resistance values to change, described by the temperature coefficient of resistance (TCR)
All resistors exhibit a temperature coefficient of resistance (TCR), meaning their resistance value changes with temperature; precision standards have very low TCR and require temperature-controlled environments.
What is the purpose of a 'guard' terminal on a precision resistance standard?
Answer: To eliminate leakage currents from affecting the measurement
The guard terminal on a precision resistance standard creates a low-impedance path for leakage currents, preventing them from flowing through the measurement circuit and causing errors in high-resistance measurements.
Which parameter is calibrated when verifying an oscilloscope's timebase accuracy?
Answer: Horizontal sweep speed (time per division)
Oscilloscope timebase calibration verifies the accuracy of the horizontal sweep speed (time/division), typically using a precision frequency reference or time interval standard.
What is 'self-heating error' in precision electrical measurements?
Answer: Resistance change in a resistive element caused by the power dissipated by the measurement current flowing through it
Self-heating error occurs when the measurement current flowing through a resistor dissipates power (I²R), raising the resistor's temperature and changing its resistance value during measurement.