Structure and principle of transformer type clamp meter
Clamp meter is an instrument that combines current transformers and ammeters, and is an important branch of digital multimeter; It is a portable instrument that can directly measure the AC current of a circuit without disconnecting the circuit.
Structure and principle
The clamp type meter is essentially composed of a current transformer, clamp type wrench, and a rectifier type magnetoelectric system reaction force instrument.
The working principle of a clamp type meter is the same as that of a transformer. The primary coil is a wire that passes through a clamp type iron core, equivalent to the primary coil of a 1-turn transformer, which is a step-up transformer. The secondary coil and the ammeter used for measurement form the secondary circuit. When there is alternating current passing through the wire, it is this turn of coil that generates an alternating magnetic field, causing induced current in the secondary circuit. The magnitude of the current and the proportion of the primary current are equivalent to the inverse ratio of the turns of the primary and secondary coils. A clamp type ammeter is used to measure large currents. If the current is not high enough, the number of turns of a wire passing through the clamp type ammeter can be increased, and the measured current can be divided by the number of turns.
The secondary winding of the through core current transformer of the clamp type ammeter is wound around the iron core and connected to the AC ammeter. Its primary winding is the measured wire passing through the center of the transformer. The knob is actually a range selection switch, and the function of the wrench is to open and close the movable part of the core of the through core transformer, in order to clamp it onto the measured wire.
When measuring current, press the wrench, open the clamp, and place the measured current carrying wire in the middle of the through core current transformer. When there is alternating current passing through the measured wire, the magnetic flux of the alternating current induces a current in the secondary winding of the transformer. This current passes through the coil of the electromagnetic ammeter, causing the pointer to deflect, and indicating the measured current value on the dial scale.
After placing the measured wire into the window through the iron core button, it is important to ensure that the two faces of the clamp are well matched and that no other objects are placed in the middle;
The z small range of the clamp meter is 5A, and when measuring a small current, the display error will be larger. This can be achieved by winding the energized wire on a clamp gauge for a few turns before measuring, and dividing the reading value by the number of turns to obtain the desired result.
