Tips for buying clamp meters
1: detection object
Choose the model according to different detection objects, AC current, DC current, or leakage current;
2: Detectable conductor specifications
According to the testing site, there are different specifications from 21mm diameter to 53mm diameter.
3: Is true value detection necessary?
The clamp ammeter using the average value mode cannot correctly detect the non-sinusoidal circuit such as the motor and the circuit of the transformer. The clamp ammeter of the true effective value mode should be used to detect this circuit.
4: Other functions
Not only can detect the current, but also a model that integrates the detection function and record output.
The clamp ammeter is called clamp meter for short. Its working part is mainly composed of an electromagnetic ammeter and a feed-through current transformer. The core of the core-through current transformer is made into a movable opening and is shaped like a clamp, so it is called a clamp ammeter. It is a portable instrument that can directly measure the AC current of the circuit without disconnecting the circuit. It is very convenient to use in electrical maintenance and widely used.
Clamp Meter Principle
The clamp meter is an instrument that integrates current and ammeter. It is an important branch of digital, and its working principle is the same as that of measuring current. A clamp meter is a combination of a current transformer and an ammeter. The iron core of the current transformer can be opened when the wrench is tightened; the wire through which the measured current passes can pass through the gap opened by the iron core without being cut off, and the iron core is closed when the wrench is released. 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 is essentially composed of a current transformer, a clamp wrench and a rectifying magnetoelectric system with a reaction force instrument.
A clamp meter works on the same principle as a transformer. The primary coil is the wire that passes through the clamp-type iron 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 loop. When the wire has an alternating current passing through it, it is this turn of the coil that generates an alternating magnetic field, and an induced current is generated in the secondary circuit. The ratio of the magnitude of the current to the primary current is equivalent to the inverse ratio of the turns of the primary and secondary coils. . The clamp ammeter is used to measure large currents. If the current is not large enough, the primary wire can be passed through the clamp meter to increase the number of turns, and at the same time divide the measured current by the number of turns.
The secondary winding of the feedthrough current transformer of the clamp 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 core of the through-type transformer so that it can clamp the wire under test.
