The clamp meter is essentially composed of a current transformer, a clamp wrench and a rectifying magnetoelectric system with reaction force meter.
The working principle of a clamp meter is the same as that of a transformer.
The primary coil is the wire passing through the pincer core, which is equivalent to the primary coil of a 1-turn transformer, which is a step-up transformer. The secondary coil and the ammeter for measurement constitute the secondary circuit.
When an alternating current passes through the wire, it is this coil that generates an alternating magnetic field, and an induced current is generated in the secondary loop. The ratio of the current to the primary current is equivalent to the inverse ratio of the turns of the primary and secondary coils. .
The clamp-type ammeter is used to measure large current. If the current is not large enough, the primary wire can be passed through the clamp-type meter to increase the number of turns, and at the same time, the measured current is divided by the number of turns.
The secondary winding of the through-core current transformer of the clamp-type ammeter is wound on the iron core and connected to the AC ammeter, and 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 iron core of the through-core transformer, so as to make it clamp the conductor under test.
When measuring the current, press the wrench, open the jaws, and place the measured current-carrying wire in the middle of the through-core current transformer, when there is an alternating current passing through the measured wire;
The magnetic flux of the alternating current induces a current in the secondary winding of the transformer, and the current passes through the coil of the electromagnetic ammeter to deflect the pointer and indicate the measured current value on the dial scale.
About the structure and principle of clamp meter
Instructions
(1) Mechanical zero adjustment is required before measurement
(2) Select the appropriate range, first select the large range, then select the small range or look at the nameplate value for estimation.
(3) When using the range measurement, when the reading is not obvious, the wire under test can be wound a few turns, the number of turns should be based on the number of turns in the center of the jaw, then the reading = indicated value × range / full deviation × number of turns
(4) After the measurement is completed, place the switch at the range.
(5) When measuring, the conductor under test should be in the center of the jaws, and the jaws should be closed tightly to reduce errors.
