Can a multimeter be used to measure the output signal of an inverter?
1, usually we say that the inverter output 380V, 50Hz, refers to its base wave (sine wave) for 380V, 50Hz. inverter actual output waveform for the PWM wave, in addition to the base wave, but also contains the carrier signal. Carrier signal frequency is much higher than the fundamental wave, and is a square wave signal, contains a large number of high harmonics.
2, ordinary multimeter can only measure 45~66Hz or 45~440Hz AC sine wave. Part of the true rms multimeter measurement frequency range is much wider, many people think that can be used for frequency measurement, testing. In fact, it is not, because this kind of table measurement results to the base wave and carrier wave are included. For example, the above frequency converter, 380V output, the measurement results are generally more than 400V.
3, for inverter test meter should have in a variety of PWM waveforms in the decomposition of its fundamental waveform ability, strict measurement needs to be used in the way of digital signal processing, that is, high-speed sampling to get the sample sequence, and then the sample sequence of the discrete Fourier transform, to get the fundamental waveform has the amplitude, phase and the harmonics of the amplitude and phase.
4, there is also a way of thinking that the calibration of the average value can be a substitute for the effective value of the fundamental waveform component of the inverter output PWM signal.
Quasi-average value (MEAN) is theoretically equal to the true RMS of a sine wave, equal to the fundamental RMS of a sinusoidally modulated PWM waveform, and is simple to realize; therefore, MEAN is used to replace the RMS of a positive harmonic (RMS) or the fundamental RMS of a PWM (H01) measurement in many instruments and meters.
However, in recent years, the frequency conversion speed control technology is changing rapidly, the application of non-sinusoidal modulation PWM is more and more, and, inverter users usually do not know what kind of modulation mode is used in their own inverters, the MEAN value in the PWM measurement of the limitations are getting bigger and bigger.
5, AnyWay broadband power test system for the user to provide a professional for frequency measurement, test, including sensors and instruments, including the overall solution.
AnyWay in the high-speed sampling based on the sampled signal spectrum analysis, real-time operation of the measured signal of the fundamental RMS (H01), the way applicable to any modulation method of PWM signals and other arbitrary sinusoidal, non-sinusoidal signals of the RMS test.
AnyWay takes the fundamental RMS test as the basic test mode, and at the same time, provides true RMS, calibrated mean (MEAN), rectified mean (RMEAN), arithmetic mean (DC, mainly used for DC measurement) and other measurement modes for users' reference.
