The structural principle of clamp ammeters and the use of clamp ammeters
A clamp type ammeter is one of the commonly used portable instruments for electricians, which measures the current value by placing a magnetic circuit that can be opened or closed on a conductor carrying the measured current. Composed of a current transformer and an ammeter, it is easy to use and can directly measure the working current of electrical equipment in operation without disconnecting the power and circuit, facilitating timely understanding of the equipment's working condition.
The structural principle of clamp ammeter
The iron core of the transformer is made into a movable opening and in the shape of a clamp. The movable part is connected to the handle 6. When the handle is tightly grasped, the iron core of the current transformer opens, and the measured cutoff wire 4 can be placed in the clamp, making the cutoff wire the primary coil of the current transformer. Close the clamp, and alternating magnetic flux passes through the iron core of the current transformer, generating induced current in the secondary winding 5 of the transformer. The ammeter is connected to both ends of the secondary winding, and the current value indicated by its pointer is proportional to the working current of the clamped cut-off wire. It can directly read the measured current value from the dial.
Special Applications of Clamp Ammeters
(1) When conducting measurements, pinch the wrench tightly with your hand to open it. The position of the measured current carrying wire should be placed in the middle of the clamp to prevent measurement errors. Then, release the wrench to close the iron core, and the meter head will have an indication.
(2) When measuring, it is necessary to first estimate the magnitude of the measured current or voltage, select an appropriate range or choose a larger range for measurement, and then reduce the range based on the magnitude of the measured current and voltage, so that the reading exceeds 1/2 of the scale, in order to obtain a more accurate reading.
(3) To ensure accurate readings, the two faces of the jaws should be well connected. If there is any noise, the jaws can be reopened and closed again. If the sound still exists, check if there is dirt on the joint surface. If there is dirt, it can be wiped clean with gasoline.
(4) When measuring the current of low-voltage fusible fuses or low-voltage busbars, adjacent phases should be isolated with insulation plates before measurement to prevent potential short circuits between phases when the jaws are opened.
(5) Some models of clamp type ammeters come with AC voltage scales, which should be measured separately when measuring current and voltage, and cannot be measured simultaneously.
(6) It cannot be used for high-voltage live measurement.
(7) After the measurement is completed, it is necessary to place the adjustment switch in the maximum current range position to avoid damage to the instrument due to unselected range in the next use.
(8) In order to obtain accurate readings when measuring currents below 5A, if conditions permit, the wire can be wound several more times and placed in the clamp for measurement. However, the actual current value should be the reading divided by the number of wires placed in the clamp.
