Voltage measurement instrument selection principle - Solutions - Huaqiang Electronic Network

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The voltage in the electronic circuit has the characteristics of wide frequency range, wide voltage range, various waveforms, coexistence of AC and DC, and even noise interference. In addition, the measurement purpose is different (engineering measurement or accurate measurement), so when formulating the measurement scheme, According to the purpose and requirements of the measurement, the measuring instrument should be reasonably selected to achieve the expected measurement result. The principle of selecting a voltage measuring instrument is:

1. Select according to the frequency range of the measured voltage

The frequency of the voltage in the electronic circuit varies from zero to hundreds of megahertz. The measuring DC voltage can be selected with a high-sensitivity multimeter or DC millivoltmeter; the operating frequency is in the range of 20Hz~1MHz, usually the transistor millivoltmeter is selected; the operating frequency is In the range of 5 to 300 MHz, an ultra-high frequency transistor millivoltmeter can be selected.

2. Select according to the range of magnitude of the measured voltage

In electronic circuits, voltage measurements of microvolts or millivolts are often encountered, so voltmeters with higher sensitivity should be used for measurement. As an engineering measurement, the DA-16 transistor millivoltmeter can meet the requirements. The multi-digit digital voltmeter has a wide voltage measurement range, but the price is high.

3. Select according to the equivalent resistance of the circuit under test

Since the input resistance of the measuring instrument is the extra load of the circuit under test, considering the influence of the instrument's access on the circuit under test, the measuring instrument is required to have a high input resistance.

4. Select according to the waveform of the measured voltage

In addition to the sinusoidal voltage measured in the electronic circuit by the transistor voltmeter, the non-sinusoidal voltage (including the pulse voltage) is often measured by the transistor voltmeter to cause a large waveform error. Therefore, the non-sinusoidal voltage value is usually measured by an oscilloscope.

5. Select according to the requirements of the circuit under test for measurement accuracy

In engineering surveys, both the accuracy requirements and the economic costs must be taken into account. Therefore, under the premise of meeting the accuracy requirements, we should try to choose instruments with low prices.

6. Notes

(1) The DC component of the measured AC voltage must not exceed the allowable value of the meter.

(2) When directly measuring the mains, it is possible to electrify the casing and must pay great attention to avoid danger.

(3) After use, the power should be turned off, the input terminal should be shorted, and the range selector switch should be placed in the maximum range.

(4) When the meter is found to be inaccurate, the meter should be calibrated.