When choosing a clamp meter, the most frequently heard questions are mostly "how accurate" and "accurate". There are many factors that affect the accuracy of a clamp meter. Design/workmanship, bandwidth, frequency response, including whether a suitable range is selected, will all affect the readings. However, among all these factors, one of the most important factors is true RMS measurement, especially for industrial users with a wide variety of electrical equipment and complex electrical environments.
Non-true RMS, that is, the average response instrument, is mainly aimed at the measurement of the sine wave of the standard power frequency. A common implementation principle is to convert the measured arithmetic mean reading x1.1 into a sine wave 'RMS' reading. This is completely fine in environments where electrification is relatively simple, such as buildings and properties.
In a wider industrial environment, especially the use of more and more frequency conversion, rectifier, inverter and other equipment, the actual waveforms are becoming more and more diverse, and even more and more high-frequency noise is introduced. Accurate measurement, true RMS becomes one of the most important factors.
When it comes to noise or harmonics, another important concept has to be mentioned: low-pass filter (LPF). The implication is that only the low-frequency current and voltage can be measured, and the high-frequency part will be cut off and not calculated. It can be said that only a true RMS clamp meter with low-pass filtering is a truly valuable 'true RMS'.
