Introduction to the current clamp application
An ammeter refers to an instrument used to measure the current in AC and DC circuits. In the circuit diagram, the symbol for the ammeter is "circle A". The current value is measured in standard units of "ampere" or "A".
An ammeter is made based on the effect of magnetic field force on an electrified conductor in a magnetic field. There is a permanent magnet inside the ammeter that generates a magnetic field between the poles. There is a coil in the magnetic field, and there are spring springs at both ends of the coil. Each spring is connected to a terminal of the ammeter, and a rotating shaft is connected between the spring and the coil. At the front end of the rotating shaft relative to the ammeter, there is a pointer. When there is current passing through, the current passes through the magnetic field along the spring and shaft, and the current cuts the magnetic induction line. Therefore, under the action of the magnetic field force, the coil deflects, driving the shaft and pointer to deflect. As the magnitude of the magnetic field force increases with the current, the current can be observed by the degree of deflection of the pointer, which is called a magneto electric ammeter.
Clamp on ammeter is a type of ammeter used to measure the current value in a circuit, abbreviated as current clamp.
In electrical and electronic engineering, a current clamp (or current probe) is a type of probe with two openable clamps used to clamp the electrical conductors around electrical equipment. The probe does not need to be in contact with the conductive parts of the equipment, that is, it does not need to disconnect the equipment wires for probe insertion, in order to measure the properties of the current in the conductor. Current clamps are commonly used to measure sine wave currents (alternating current (AC)). Combined with more advanced detection instruments, phase and waveform can also be tested. Generally speaking, very high alternating current (above 1000A) is easy to measure, while direct current and very low alternating current (milliampere level) are difficult to measure accurately.
Usually, when measuring current with a regular ammeter, the circuit needs to be cut off before the ammeter can be connected for measurement, which is very troublesome. Sometimes, this is not allowed for motors that are running normally. At this point, using a clamp type ammeter becomes much more convenient as it can measure current without cutting off the circuit.
The tested circuit wire passing through the iron core becomes the primary coil of the current transformer, and current is induced in the secondary coil through the current. So that the ammeter connected to the secondary coil can indicate the current of the tested circuit. The clamp gauge can be changed to different ranges by shifting the switch. But it is not allowed to operate with electricity when shifting gears.
