Multimeter to measure the rms value of voltage and current
There are three cases of the effective value of the multimeter:
1. The calibration average method, the calibration average value is also called the corrected average value, or the rectified average value calibrated to the effective value. Multiply by a factor that, for a sine wave, equals the rms value of the sine wave. Therefore, this method is limited to sine wave testing.
2. In the peak detection method, the peak value of the AC signal is obtained through the peak detection circuit, and then multiplied by a coefficient according to the characteristics of the sine wave. For the sine wave, after multiplying the coefficient, the result is equal to the effective value of the sine wave. Therefore, this method is limited to sine wave testing.
3. The true RMS method uses a true RMS circuit to convert the AC signal into a DC signal and then measure it. This method is suitable for the true RMS test of arbitrary waveforms. Most multimeters use the first two methods. And there is a big limit on the frequency of the signal.
