Multimeter for true RMS
The quantities that describe the magnitude of alternating current include peak (and peak to peak), average, and effective value, with peak being the maximum value; The average value is the average of the rectified AC power over one cycle; The effective value is also known as the root mean square value (formula on the first floor). Effective value: If direct current and alternating current are passed through two identical resistive devices, and the heat generated by them is equal at the same time, then the voltage and current of this direct current are taken as the effective value of this alternating current. So people generally refer to the effective values of voltage and current unless otherwise specified. There is a certain relationship between the three: the ratio of the effective value to the average value is called the waveform factor KF; The ratio of peak to effective value is called peak factor KP. For sine waves, the crest factor KP=root 2 (constant), and the waveform factor KF=2 times root 2 (constant). And for non sinusoidal values, it will change. It is obvious that people are concerned about the effective value, but it is difficult to measure, while the average and peak values are easy to measure. Therefore, ordinary multimeters (including voltmeters, etc.) indirectly measure the effective value (according to the relationship of sine waves) by measuring the average or peak value. As for the peak measurement table, if the measured value is 10V, it should display 7.07V (effective value). These two types of meters display valid values, but measure "false" valid values. Obviously, using these types of meters to measure sine waves is still relatively accurate, but measuring non sine waves is incorrect. A more accurate table can directly measure the effective value (there are many methods), which means that it displays the effective value and measures the effective value. Therefore, this type of table produces correct results regardless of the waveform being measured. To distinguish between the first two tables, it is called true significant value.
