CCT CCT Electrical & Electronic Calibration 2

Question 1

What is the primary use of a Josephson junction array in electrical metrology?

Accepted Answer

Realizing the SI unit of voltage with quantum-level accuracy

Answer

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.

Question 2

When calibrating an insulation resistance tester (megohmmeter), what type of reference standard is used?

Accepted Answer

A precision resistor with a known high-resistance value

Answer

High-value precision resistors with known, stable resistance values (often in the megaohm to gigaohm range) are used as reference standards when calibrating megohmmeters.

Question 3

What effect does temperature have on precision resistors used as calibration standards?

Accepted Answer

Temperature causes resistance values to change, described by the temperature coefficient of resistance (TCR)

Answer

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.

Question 4

What is the purpose of a 'guard' terminal on a precision resistance standard?

Accepted Answer

To eliminate leakage currents from affecting the measurement

Answer

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.

Question 5

Which parameter is calibrated when verifying an oscilloscope's timebase accuracy?

Accepted Answer

Horizontal sweep speed (time per division)

Answer

Oscilloscope timebase calibration verifies the accuracy of the horizontal sweep speed (time/division), typically using a precision frequency reference or time interval standard.

(CCT) Certified Calibration Technician Practice Test

(CCT) Certified Calibration Technician Practice Test

CCT CCT Electrical & Electronic Calibration 2