Square AC voltmeter 84L4-V refers to a meter used to measure the effective value of AC voltage. In the field of strong electricity, AC voltmeters are often used to measure the voltage of the monitoring line.
The selection of common AC voltmeters should generally make the displayed value about 2/3 of the full scale of the dial. For example, 380V should use a voltmeter with a full scale of 500V, and 220V applications should choose a voltmeter with a full scale of 300V or 400V. High voltage voltmeters are used together with voltage transformers. For example, 6kV should use the voltmeter marked 6000/100 on the dial, and 10kV should use the 10,000 / 100 voltmeter marked on the dial. We call 6000/100 and 10000/100 the transformation ratio, and the transformation ratio of the voltage transformer is the same. The wiring of AC voltmeters is non-polar, but in a system, all voltmeter wiring should be consistent, especially 220V or voltmeters using transformers must comply with this rule. The AC voltmeter and its voltage transformer circuit must be equipped with fuses to prevent short circuits.
Embeddedly installed on ships, locomotives, power stations, mines, metallurgy, petrochemicals or other mobile power equipment, measuring AC current voltages with rated operating frequencies of 50, 400, and 427 Hz.