The effective value of a multimeter usually refers to one of the following three situations:
1. The method of calibrating the average value, also known as the corrected average value or the rectified average value calibrated to the effective value, is based on the principle of converting an AC signal into a DC signal through rectification and integration circuits, and then multiplying it by a coefficient according to the characteristics of a sine wave. For a sine wave, the result of multiplying by this coefficient is equal to the effective value of the sine wave. Therefore, this method is limited to sine wave testing only.
2. Peak detection method obtains the peak value of an AC signal through a peak detection circuit, and then multiplies it by a coefficient based on the characteristics of a sine wave. For a sine wave, the result of multiplying by this coefficient is equal to the effective value of the sine wave. Therefore, this method is limited to sine wave testing only.
3. The true effective value method uses a true effective value circuit to convert AC signals into DC signals before measurement. This method is applicable for testing the true effective value of any waveform.
Most multimeters use the first two methods. And there are significant limitations on the frequency of the signal.
For AC power, its voltage is a changing waveform, and we usually describe its voltage value as its effective value. For example, when we talk about 220V power supply, its peak voltage is over 310 volts, and the peak to peak value is twice the peak value, which is over 600 volts.
The effective values of electromotive force, voltage, and current of sinusoidal alternating current are represented by E, U, and I, respectively. The mean effective value of the magnitude of the electromotive force, voltage, and current commonly referred to as alternating current. The rated values marked on AC electrical equipment and the values indicated on AC meters are also valid values.
