Analyzing the Working Principle of the Clamp Ammeter from the Internal Structure
The clamp meter is mainly composed of an electromagnetic ammeter and a feed-through current transformer. The secondary winding of the feedthrough current transformer 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. When measuring the current, press the wrench, open the jaws, and place the measured current-carrying wire in the middle of the feed-through current transformer. A current is induced in the side winding, and the current passes through the coil of the electromagnetic ammeter, causing the pointer to deflect, and the measured current value is indicated on the dial scale. The clamp ammeter must be connected in series with the circuit under test.
In actual operation, the line has to be disconnected, which is obviously very inconvenient. The clamp-on ammeter 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 is widely used.
The clamp meter 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.
Current knowledge
1. The neutral current of the star connection circuit is equal to the phase current.
2. The current in the neutral line of the delta connection method is equal to the double phase current.
3. Calculate the rated current according to the power P of the equipment; Three-phase motor 1KW≈2A Single-phase power consumption 1KW≈4.5A
(A) The tester should wear gloves, hold the meter flat and open the jaws.
(B) Make the wire under test enter the jaws and then close the jaws.
(C) Clamp two wires at the same time, then the indicated current value should be the current of the third wire.
(D) If in a three-phase four-wire system, three phase wires are simultaneously clamped for measurement, the indicated current value should be the current value on the working zero line.
(E) If the current on the wire is too small, the deflection angle of the needle is still very small even if it is measured at the lowest current level (so the reading is inaccurate), you can coil the wire on the clamp arm for several turns (as shown in the figure for four Turns) after measurement, divide the reading by the number of turns, which is the actual measured current of the wire under test.
