Clamp ammeter referred to as clamp meter, is a set of current transformer and ammeter in one instrument, its working principle and current transformer current measurement is the same. Its working part mainly consists of an electromagnetic ammeter and through-centre type current transformer. Through the heart type current transformer core made of movable openings, and into a clamp, so the name clamp ammeter. Is not required to disconnect the circuit can be directly measured circuit AC current portable instrumentation, electrical maintenance in the use of very convenient, widely used.
The working principle of the clamp meter is the same as that of the transformer. The primary coil is through the clamp core wire, equivalent to 1 turn of the primary coil of the transformer, which is a step-up transformer. The secondary coil and the ammeter used for measurement form the secondary circuit. When the wire has an alternating current through, it is this turn of the coil produces an alternating magnetic field, in the secondary circuit produces an induced current, the size of the current and the ratio of the primary current, which is equivalent to the inverse ratio of the number of turns of the primary and secondary coils. Clamp ammeter is used to measure large currents, if the current is not large enough, you can increase the number of turns of the primary conductor in through the clamp meter, at the same time the number of measured current divided by the number of turns. Clamp ammeter through the core of the current transformer winding on the secondary side of the core and connected to the AC ammeter, its primary winding that is through the centre of the transformer measured wire. The knob is actually a range selector switch, and the role of the spanner is to open and close the movable part of the core of the core transformer in order to make it clamp the measured wire. Measurement of current, press the spanner, open the jaws, the measured current-carrying conductor placed in the middle of the wear-centred current transformer, when the measured conductor has an alternating current through the alternating current flux in the transformer vice-side of the winding induces a current, which passes through the coil of the electromagnetic ammeter, so that the pointer is deflected in the dial scale pointed out that the measured current value.
Clamp meter can be changed to different ranges by switching gears. However, the dialling is not allowed to be operated with electricity. Clamp meter general accuracy is not high, usually 2.5 ~ 5 level. In order to facilitate the use of the table, there are different ranges of switch for measuring different levels of current and voltage measurement function. Clamp meter was initially used to measure AC current, but now the multimeter has the function it also has, can measure AC and DC voltage, current, capacitance, diode, transistor, resistance, temperature, frequency and so on.
