Hot Selling Three Phase /Single Phase Intelligent Digital Current Meter Voltage Meter Multi-Function Digital Panel Meter

When measuring current, the ammeter should be connected in series with the circuit under test; When measuring voltage, the voltmeter should be connected in parallel with the circuit under test. When measuring DC current and voltage, attention must be paid to the polarity of the instrument, and the polarity of the instrument should be consistent with the measured polarity. Measurement of high voltage and high current. When measuring high voltages or currents, voltage transformers or current transformers must be used. The range of the voltmeter and ammeter should match the secondary rating of the transformer. The general voltage is 100V and the current is 5A.

Generally, it is possible to directly measure currents in the order of microamps or milliamps. To measure larger currents, the ammeter should have a parallel resistor (also known as a shunt). The measurement mechanism mainly uses a magnetoelectric electric meter. The resistance value of the shunt is such that when the full range current passes through, the ammeter deflects fully, i.e. the ammeter indication reaches the maximum. For a few amperes of current, a dedicated shunt can be installed in the ammeter. For currents above a few amperes, an external shunt is used. The resistance value of a large current shunt is very small. To avoid errors caused by the addition of lead resistance and contact resistance to the shunt, the shunt should be made into a four-terminal form, that is, with two current terminals and two voltage terminals.