Analyzing the working principle of a clamp ammeter from its internal structure
The clamp meter mainly consists of an electromagnetic ammeter and a through core current transformer. The secondary winding of the through core 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 the current, press the wrench, open the clamp, and place the measured current carrying wire in the middle of the through core current transformer. When there is alternating current passing 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 actual operation, it is obviously inconvenient to disconnect the circuit. The clamp shaped ammeter, on the other hand, 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 type 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 core transformer, so as to clamp it onto the measured wire.
Common faults of clamp ammeters
(1) When measuring current or voltage, one or several levels have no indication, while other levels have normal indications. The reason is that the fastening switch screw of the clamp type meter is loose, or the connection on its branch switch is twisted. This type of fault is common. After opening the cover, the broken wire can be connected properly.
(2) The current reading is relatively small, while the voltage reading is normal. Most of the reasons are due to poor contact between the jaws and excessive magnetic leakage. The jaws should be corrected to ensure good contact. This type of fault is sometimes caused by a short circuit between windings, which is more troublesome. Generally, it is necessary to rewind according to the original data and undergo aging treatment
(3) The reading of the current and voltage ranges is low, which often occurs on internal magnetic clamp type ammeters. The reason is that the magnet demagnetizes and should generally be magnetized to solve the problem. It can also be adjusted by reducing the resistance value connected in series with the meter head branch
(4) If one of the readings is inaccurate, the corresponding resistance should be adjusted
(5) The voltage level indication is normal, but the current level is not indicated. Use a multimeter to check the primary switch and secondary winding for any abnormalities
(6) There is no indication at all. The rectifier diode, meter head, switch, and wiring connected to or related to the clamp meter should be checked for any breaks
