Three situations of effective values of multimeter
The meaning of valid values in a multimeter
For alternating current, its voltage is a changing waveform, and the voltage value usually used to describe it refers to its effective value. For example, in a 220V power supply, the peak voltage is more than 310 volts, and the peak-to-peak voltage is more than 600 volts.
The meaning of valid values in a multimeter
1. Effective value: defined by heat (power). A certain alternating current generates heat through a resistor and another direct current passes through the resistor. If the heat generated in the same time is equal, then the DC voltage value is the alternating current. The effective value of the voltage.
2. True effective value: The definition of effective value is defined by heat generation, but it is difficult to measure the effective value voltage in measuring instruments using this method. Therefore, in most voltage measuring instruments, such as multimeters measuring voltage, The measurement method is not based on the "heat" defined by the effective value. One type of multimeter uses the sine wave as a reference and obtains the effective value (or Deduced from the average value), the effective value obtained by this method is only correct for AC voltages such as sinusoidal waveforms, and will cause deviations for waveforms of other shapes.
Another type of multimeter voltage value is calculated by the square of the effective value of the DC component, fundamental wave and each higher harmonic. This value is similar to the effective value definition. There is no requirement for the shape of the waveform. In order to distinguish this type of effective value from the The difference between the sine wave and the effective value of the instrument is found, and this wave is called the "true effective value" in the measuring instrument.
3. Root mean square value: Another name for the effective value (which should be the true effective value on the measuring instrument).
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The meaning of the effective value of a multimeter_Three situations of the effective value of a multimeter
Source: Electrician World Time: 2021-05-19 09:12:32 Author: Old Electrician Mobile Version >>
Regarding the meaning of the effective value, true effective value and root mean square value in the multimeter, as well as the three situations of the effective value of the multimeter: standard average method, peak detection method, and true effective value method.
The meaning of valid values in a multimeter
For alternating current, its voltage is a changing waveform, and the voltage value usually used to describe it refers to its effective value. For example, in a 220V power supply, the peak voltage is more than 310 volts, and the peak-to-peak voltage is more than 600 volts.
The meaning of valid values in a multimeter
1. Effective value: defined by heat (power). A certain alternating current generates heat through a resistor and another direct current passes through the resistor. If the heat generated in the same time is equal, then the DC voltage value is the alternating current. The effective value of the voltage.
2. True effective value: The definition of effective value is defined by heat generation, but it is difficult to measure the effective value voltage in measuring instruments using this method. Therefore, in most voltage measuring instruments, such as multimeters measuring voltage, The measurement method is not based on the "heat" defined by the effective value. One type of multimeter uses the sine wave as a reference and obtains the effective value (or Deduced from the average value), the effective value obtained by this method is only correct for AC voltages such as sinusoidal waveforms, and will cause deviations for waveforms of other shapes.
Another type of multimeter voltage value is calculated by the square of the effective value of the DC component, fundamental wave and each higher harmonic. This value is similar to the effective value definition. There is no requirement for the shape of the waveform. In order to distinguish this type of effective value from the The difference between the sine wave and the effective value of the instrument is found, and this wave is called the "true effective value" in the measuring instrument.
3. Root mean square value: Another name for the effective value (which should be the true effective value on the measuring instrument).
Three situations of effective values of multimeter:
1. Calibration average method. The calibration average is also called the corrected average, or the rectified average calibrated to the effective value. The principle is to convert the AC signal into a DC signal through the rectification and integration circuit, and then according to the characteristics of the sine wave, Multiply by a factor that, for a sine wave, equals the effective value of the sine wave. Therefore, this method is limited to sine wave testing.
2. Peak detection method, through the peak detection circuit, obtains the peak value of the AC signal, and then multiplies it by a coefficient according to the characteristics of the sine wave. For the sine wave, after multiplying 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, which uses a true RMS circuit to convert the AC signal into a DC signal before measuring. This method is applicable to the true effective value test of arbitrary waveforms. Most multimeters use the first two methods. And there are great restrictions on the frequency of the signal.
