Analyze the working principle of the clamp ammeter from its internal structure
The shape meter mainly consists of an electromagnetic ammeter and a through type current transformer. The secondary winding of the through type current transformer is wound around 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 current, press the wrench, open the clamp, and place the measured current carrying wire in the middle of the through type current transformer. When an alternating current passes through the measured wire, the magnetic flux of the alternating current induces a current in the secondary winding of the transformer. This current passes through the coil of the electromagnetic ammeter, causing the pointer to deflect and indicating the measured current value on the dial scale. The clamp ammeter must be connected in series with the circuit being tested.
In practical operation, it is obviously inconvenient to disconnect the line. The clamp type ammeter is a portable instrument that can directly measure the AC current of a circuit without disconnecting it. It is very convenient to use in electrical maintenance and has a wide range of applications.
The clamp 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 as to clamp the measured wire.
Common faults of clamp current meter
(1) When measuring current or voltage, there is no indication for one or several gears, while other gears indicate normally. The reason is that the fastening switch screw of the clamp meter is loose, or the wire on its distribution switch is twisted and broken. This type of fault is most common, and the broken wire can be connected after opening the cover.
(2) The current reading is too small, while the voltage reading is normal. The reason for this is mostly due to poor contact between the jaws and excessive magnetic leakage. The jaws should be corrected to ensure good contact. Sometimes, this fault is caused by a short circuit between the windings, which can be troublesome. Generally, it is necessary to re wind according to the original data and undergo aging treatment
(3) The readings of the current and voltage levels are both low, which often occurs on the internal magnetic clamp meter. The reason is that the magnet demagnetizes, and it should generally be magnetized to solve the problem. It can also be adjusted by reducing the resistance value in series with the meter branch
(4) One of the readings is inaccurate, and the corresponding resistor should be adjusted
(5) The voltage level indication is normal, but there is no indication for the current level. Use a multimeter to check the primary switch and secondary winding for any abnormal phenomena
(6) There is no indication at all. The rectifier diode, meter head, switch, and wiring connected or related to the clamp meter should be checked for any breaks
