The Fluke 87V Meter measures the ______ of a voltage or current signal by counting the number of times the signal crosses a threshold level each second.

• A. Amplitude
• B. Phase
• C. Duty cycle
• D. By counting the number of times the signal crosses a threshold per second

Answer: (D)

Measuring how often a repeating signal repeats itself by counting how many times it crosses a fixed reference level each second. The Fluke 87V uses this approach in its frequency function: it watches the waveform and increments a count each time the signal crosses the reference level (often around zero volts for AC). That crossing rate translates into cycles per second (hertz). This is different from amplitude (how tall the peaks are), phase (timing relative to another signal), or duty cycle (the fraction of time the signal stays high in a cycle). With a clean waveform, the crossing count provides an accurate frequency; noise or distorted shapes can affect the readout.