Current Clamp Application Introduction
Ammeter refers to the 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 in "A" or "A" as the standard unit.
The ammeter is made according to the action of the current-carrying conductor in the magnetic field by the magnetic field force. There is a permanent magnet inside the ammeter, which generates a magnetic field between the poles. There is a coil in the magnetic field. There is a hairspring spring at both ends of the coil. Each spring is connected to a terminal of the ammeter. The spring and the coil are connected by a rotating shaft. On the front of the ammeter, there is a pointer. When a current flows, the current passes through the magnetic field along the spring and the rotating shaft, and the current cuts the magnetic induction line. Therefore, under the action of the magnetic field force, the coil is deflected, which drives the rotating shaft and the pointer to deflect. Since the magnitude of the magnetic field force increases with the increase of the current, the magnitude of the current can be observed through the deflection of the pointer, which is called a magnetoelectric ammeter.
Clamp-on ammeter is a kind of ammeter, which is used to measure the current value in the circuit, referred to as current clamp.
In electrical and electronic engineering, a current clamp (or current probe) is a probe with two openable clamps, which is used to clamp electrical conductors around electrical equipment, and the probe does not need to be in contact with the conductive part of the equipment, that is, it does not need to be disconnected The device lead is used for probe insertion to measure the properties of the current flowing through the conductor. Current clamps are commonly used to measure sinusoidal currents (alternating current (AC)). Cooperating with more advanced testing instruments, phase and waveform can also be tested. Generally speaking, very high AC current (above 1000A) is easy to measure, while DC current and very low AC current (milliamp level) are difficult to measure accurately.
Usually, when using an ordinary ammeter to measure the current, the circuit needs to be cut off before the ammeter can be connected for measurement, which is very troublesome, and sometimes a normal operating motor does not allow this. At this time, it is much more convenient to use a clamp-on ammeter, which can measure the current without cutting off the circuit.
The measured circuit wire passing through the iron core becomes the primary coil of the current transformer, and the current is induced in the secondary coil by passing the current. So that the ammeter connected to the secondary coil has an indication ----- measure the current of the line under test. The clamp meter can be changed to different ranges by changing the gear of the switch. But it is not allowed to operate with electricity when shifting gears.
The clamp meter is generally not high in accuracy, usually 2.5 to 5 grades. For the convenience of use, there are switches of different ranges in the meter for the function of measuring different levels of current and measuring voltage.
