Introduction to the Use of Current Clamp
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 amperes or amperes.
An ammeter is made based on the effect of magnetic field force on an energized conductor in a magnetic field. There is a permanent magnet inside the ammeter that generates a magnetic field between the poles. In the magnetic field, there is a coil with a wire spring at each end of the coil, which is connected to a terminal of the ammeter. The spring is connected to the coil by a shaft, and there is a pointer relative to the front end of the ammeter on the shaft. 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 magnetic field force increases with the increase of current, the magnitude of current can be observed by the degree of deflection of the pointer, which is called a magneto electric ammeter.
A clamp ammeter is a type of ammeter used to measure the current value in a circuit, abbreviated as a current clamp.
In electrical and electronic engineering, current clamps (or current probes) are two clamp type probes that can be opened to clamp the electrical conductors around electrical equipment, and the probes do not need to come into contact with the conductive parts of the equipment, that is, they do not need to disconnect the equipment wires for probe insertion, to measure the properties of current in the conductors. Current clamp is commonly used to measure sinusoidal current (alternating current (AC)). Combined with more advanced detection instruments, it can also test phase and waveform. Generally speaking, very high AC current (above 1000A) is easy to measure, while DC current and very low AC current (milliampere level) are difficult to measure accurately.
Usually, when measuring current with a regular ammeter, it is necessary to cut off the circuit before connecting the ammeter for measurement, which is very troublesome. Sometimes, normally running motors are not allowed to do so. 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 the current is induced in the secondary coil through the current. So that the ammeter connected to the secondary coil has an indication - to measure the current of the tested circuit. The clamp meter can be changed to different ranges by shifting the gear of the switch. But it is not allowed to operate with electricity when shifting gears.
