Test Equipment and Measurement Techniques
Core concepts
Know the purpose and proper use of the multimeter, oscilloscope, signal generator, power supply, and tone generator/probe. A voltmeter is connected in parallel with the component and should have high input impedance; an ammeter is inserted in series and should have low resistance. The oscilloscope measures amplitude and time; understand volts/div, time/div, triggering, and probe compensation. Know the difference between peak, peak-to-peak, RMS, and average for a sine wave: V_rms = 0.707 × V_peak, V_pp = 2 × V_peak. Understand decibels as a ratio (dB = 20 log(V2/V1) for voltage, 10 log(P2/P1) for power). Recognize that meter accuracy, resolution, and burden voltage affect readings, and that a wrong range or wrong jack produces misleading results.
Traps
Questions test whether you connect a meter correctly (series versus parallel) and whether you interpret RMS versus peak. Another trap is reading a scope trace without multiplying by the probe attenuation (10×). Distractors often confuse dB voltage and dB power factors of 20 versus 10. Also watch for questions about measuring resistance in a live circuit, which gives false readings.
Worked example
A sine wave on a scope spans 6 divisions peak-to-peak at 2 V/div with a 10× probe. Actual V_pp = 6 × 2 × 10 = 120 V. Peak = 60 V, RMS = 0.707 × 60 ≈ 42.4 V. Rule of thumb: always state probe attenuation before converting scope divisions to volts, and remember a 10× probe divides the displayed signal by 10.