Clamp Meter (Clamp Meter) Usage and Precautions
Clamp meter is essentially made up of a current transformer, a clamp spanner and a rectified magneto-electric system with a reaction force meter.
A clamp meter works on the same principle as a transformer. The primary coil is the wire that passes through the clamp 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 form the secondary circuit. When the wire has an alternating current through, it is this turn of the coil produces an alternating magnetic field, in the secondary circuit produces an induced current, the size of the current and the ratio of the primary current, which is equivalent to the inverse ratio of the number of turns of the primary and secondary coils. Clamp ammeter is used to measure large currents, if the current is not large enough, you can increase the number of turns of the primary conductor in through the clamp meter, at the same time the number of measured current divided by the number of turns.
Clamp ammeter through the core of the current transformer winding on the secondary side of the core and connected to the AC ammeter, its primary winding that is through the centre of the transformer measured wire. The knob is actually a range selector switch, and the role of the spanner is to open and close the movable part of the core of the core transformer in order to make it clamp the measured wire.
Measurement of current, press the spanner, open the jaws, the measured current-carrying wires placed in the middle of the wear-centre type current transformer, when the measured conductor has an alternating current through the alternating current flux in the transformer vice-side of the winding induces a current, which passes through the coil of the electromagnetic ammeter, so that the pointer is deflected in the dial scale pointed out that the measured current value.
Usage
(1)Zero mechanically before measurement.
(2) Choose the appropriate range, first select the large, then select the small range or look at the nameplate value to estimate.
(3) When using the minimum range measurement, the reading is not obvious, the measured wire can be wound around a few turns, the number of turns to the jaws of the central number of turns shall prevail, then the reading = indication value × range / full bias × number of turns
(4) Measurement is complete, to put the changeover switch on the * large range.
(5) Measurement, the measured wire should be in the centre of the jaws, and make the jaws close tightly to reduce the error.
Precautions
(1) The voltage of the measured line should be lower than the rated voltage of the clamp meter.
(2) When measuring the current of high voltage line, wear insulated gloves, insulated shoes and stand on insulated mat.
(3) Clamp jaws should be closed tightly can not be charged to change the range
The use of electrician measuring clamp meter and the use of precautions
Clamp ammeter is divided into high and low voltage two kinds, used in the case of not dismantling the line to directly measure the current in the line. Its use is as follows:
(1) the use of high-voltage clamp meter should pay attention to the voltage level of the clamp ammeter, is strictly prohibited to use low-voltage clamp meter to measure the current of high-voltage circuits. Measurement with a high-voltage clamp meter should be operated by two people, non-duty personnel measurement should also fill out the first work ticket, measurement should wear insulated gloves, stand on insulating mats, and shall not touch other equipment in order to prevent short-circuit or grounding.
(2) Observe the meter time, pay special attention to maintain a safe distance between the head and the charged part, the distance between any part of the human body and the charged body shall not be less than the whole length of the clamp meter.
(3) When measuring on the high-voltage circuit, it is prohibited to use a wire to connect another meter from the clamp-on ammeter to measure. Measurement of high-voltage cable current of each phase, the distance between the cable head line should be more than 300mm, and good insulation, to be considered convenient to measure before.
(4) Measurement of low-voltage fusible fuse or horizontally arranged low-voltage busbar current, should be measured before the phases of fusible fuse or busbar with insulating materials to protect the isolation, so as not to cause phase-to-phase short circuit.
(5) Measurement is strictly prohibited when one phase of the cable is grounded. Prevent the occurrence of low insulation level due to the cable head to ground breakdown explosion and endanger personal safety.
(6) Clamp ammeter measurement after the end of the switch to the maximum range gear, so as to avoid the next use of inadvertent overcurrent; and should be stored in a dry room
