How to use voltmeter？
A voltmeter is an instrument for measuring voltage. The symbol of a commonly used voltmeter-voltmeter is "V". The traditional pointer-type voltmeter includes a sensitive ammeter. There is a permanent magnet in the sensitive ammeter. A coil made of wire is connected in series between the two terminals of the ammeter. The coil is placed in the magnetic field of the permanent magnet and Connected with the pointer of the watch through the transmission device. Most voltmeters are divided into two ranges. The voltmeter has three binding posts, a negative binding post, and two positive binding posts. The positive terminal of the voltmeter is connected to the positive terminal of the circuit, and the negative terminal is connected to the negative terminal of the circuit.
The traditional pointer voltmeter and ammeter are based on a principle that is the magnetic effect of current. The greater the current, the greater the magnetic force generated, which is the greater the swing of the pointer on the voltmeter. There is a magnet and a wire coil in the voltmeter. After passing the current, the coil will generate a magnetic field. After the coil is energized The deflection occurs under the action of the magnet, which is the header part of the ammeter and voltmeter. .
Because the voltmeter should be connected in parallel with the measured resistance, if the ampere meter is used directly as the voltmeter, the current in the meter is too large, which will burn the meter. At this time, a large resistance needs to be connected in series in the internal circuit of the voltmeter.
After this modification, when the voltmeter is connected in parallel in the circuit again, due to the effect of resistance, most of the voltage applied to the two ends of the ammeter is shared by the series resistance, so the current through the ammeter is actually very small, so It can be used normally. The symbol of the DC voltmeter should add a "_" under V, and the symbol of the AC voltmeter should add a wavy line "~" under V.