Usage of True RMS Multimeter
True RMS: The definition of RMS is defined by heat generation, but it is difficult to realize the measurement of RMS voltage in measuring instruments according to this method, so most of the voltage measuring instruments, such as multimeter to measure the voltage, the measurement method is not according to the definition of RMS "heat generation" to carry out the measurement, one class of multimeters to Sine wave as a reference, through the peak of the sine wave for the root of two times the effective value of the relationship between the effective value to get (or through the average value to derive), this kind of method to get the effective value of the sinusoidal shape of the class of AC voltages is only correct, for other shapes of waveforms will produce bias. Another type of multimeter voltage value is the DC component, the fundamental waveform and the high harmonics of the RMS squared, this value is similar to the definition of the RMS value, the shape of the waveform is not required, in order to distinguish between this type of RMS value and the RMS value through the sinusoidal waveform instrumentation, in the measurement of instrumentation in the popular called the "true RMS value".
Root-mean-square value: RMS value (in the measurement instrument should be the true RMS value) of another way to call.
Multimeter how to measure the rms value of voltage and current
The RMS value of a multimeter usually refers to one of the following three cases:
1, the calibration average method, the calibration average is also known as the corrected average, or calibrated to the effective value of the rectified average, the principle is to rectify and integrate the circuit, the AC signal into a DC signal, and then according to the characteristics of the sine wave, multiplied by a coefficient, for the sinusoidal wave, multiplied by the coefficient, the result is equal to the RMS value of the sinusoidal wave. Therefore, this method is limited to sine wave testing.
2, peak detection method, through the peak detection circuit, to obtain the peak value of the AC signal, and then according to the characteristics of the sine wave, multiplied by a coefficient, for the sine wave, multiplied by the coefficient, the result is equal to the effective value of the sine wave. Therefore, this method is limited to sine wave testing.
3、True RMS method, the use of true RMS circuit, the AC signal into DC signal and then measured. This method is applicable to the true RMS test of arbitrary waveforms.
Most multimeters use the first two methods. And there is a large limitation on the frequency of the signal.
