CET Test Equipment and Measurements 2 — Questions and Answers
Question 1: On an oscilloscope, the timebase (horizontal axis) represents:
- Frequency in Hertz
- Amplitude in volts
- Time in seconds per division (Correct answer)
- Phase in degrees
Correct answer: Time in seconds per division
The horizontal (X) axis of an oscilloscope is the timebase, calibrated in time units (seconds, ms, or µs) per division.
Question 2: What is the typical input impedance of a standard 1X oscilloscope probe?
- 50 ohms
- 600 ohms
- 1 megohm (Correct answer)
- 10 megohms
Correct answer: 1 megohm
A standard 1X probe presents 1 megohm of input impedance to minimize circuit loading during measurements.
Question 3: If a 10X oscilloscope probe is used and the scope display reads 5V, what is the actual signal voltage?
- 0.5V
- 5V
- 50V (Correct answer)
- 15V
Correct answer: 50V
A 10X probe attenuates the signal tenfold before the scope input, so the actual voltage is 10 times the displayed value: 5V × 10 = 50V.
Question 4: A decibel (dB) measurement expresses:
- An absolute voltage level referenced to zero
- A logarithmic ratio between two power or voltage levels (Correct answer)
- A frequency measured in Hertz
- A time duration in microseconds
Correct answer: A logarithmic ratio between two power or voltage levels
The decibel is a dimensionless logarithmic ratio comparing two power or voltage levels, not an absolute quantity.
Question 5: What power level does 0 dBm represent?
- 0 mW
- 0.5 mW
- 1 mW (Correct answer)
- 10 mW
Correct answer: 1 mW
0 dBm is defined as a power of 1 milliwatt; it is the 0 dB reference point on the dBm scale.
Question 6: Which multimeter setting must be selected to accurately measure AC line voltage?
- DC voltage (DCV)
- AC voltage (ACV) (Correct answer)
- Resistance (Ω)
- DC current (DCA)
Correct answer: AC voltage (ACV)
AC line voltage must be measured with the AC voltage (ACV) setting, since DC settings cannot properly respond to alternating waveforms.
Question 7: What does a frequency counter measure?
- The peak voltage of a signal
- The number of complete cycles per second (Correct answer)
- The power consumed by a circuit
- The phase difference between two signals
Correct answer: The number of complete cycles per second
A frequency counter counts complete waveform cycles per second, displaying the result in Hertz (Hz).
CET Test Equipment and Measurements 2
On an oscilloscope, the timebase (horizontal axis) represents: