Little knowledge about digital AC ammeter
AC ammeter is a new generation of programmable intelligent instrument. It adopts large-scale integrated circuit and high-brightness and long-life LED display, and applies digital sampling technology to measure the phase voltage, line voltage, phase current, line current, active power Real-time measurement display and control of power, reactive power, apparent power, frequency, power factor, active energy, reactive energy and four-quadrant energy.
The AC ammeter mainly adopts the measuring mechanism of the electromagnetic system ammeter, the electric system ammeter and the rectifier type ammeter. The low range of the measuring mechanism of the electromagnetic system is about tens of milliamperes. In order to increase the range, the number of coil turns should be reduced proportionally and the wire should be thickened. When the ammeter is composed of an electric system measuring mechanism, the moving coil and the static coil are connected in parallel, and its low range is about tens of milliamperes. In order to increase the range, the number of turns of the static coil should be reduced, and the wire should be thickened, or the two static coils should be connected in parallel instead of series, then the range of the ammeter will be doubled. When measuring AC current with a rectifier ammeter, the ammeter reading is correct only when the AC is a sine wave. A shunt can also be used to expand the measuring range. In addition, high-frequency currents can also be measured with thermoelectric meters. Most of the large-range AC ammeters used in power systems are 5A or 1A electromagnetic ammeters, and are equipped with current transformers with appropriate current transformation ratios.
The difference between DC and AC
DC ammeters and AC ammeters are very different, and measurements cannot be exchanged, and there is no way to exchange measurements. For high-current ammeters, a DC ammeter is actually just a 75 millivolts DC voltmeter (which measures the millivolts on the shunt. volts), and the internal resistance of the AC ammeter is very small (the measurement is the short-circuit current of the secondary of the transformer), which is a short circuit for the circuit, and the current can allow AC 5 amperes to flow.
