Brief introduction and use of clamp ammeter
It is worth noting that because the principle of the clamp ammeter is to use the principle of the transformer, whether the iron core is closed tightly or whether there is a large amount of residual magnetism has a great influence on the measurement results. When measuring a small current, the measurement error will increase. . At this time, the measured wire can be wound several times on the iron core to change the current ratio of the transformer to increase the current range.
The principle of the clamp ammeter is based on the working principle of the current transformer. When the iron core of the wrench is loosened and closed, an induced current is generated on the secondary winding according to the principle of the transformer, and the pointer of the ammeter deflects, thereby indicating the measured The value of the current. When the clamp ammeter wrench is gripped tightly, the iron core of the current transformer can be opened, and the wire of the measured current enters the inside of the jaw as the primary winding of the current transformer.
The following points should be paid attention to when using the clamp ammeter:
When observing the timing of the watch, special attention should be paid to keeping the maximum distance between the head and the charged part. The distance between any part of the human body and the charged body should not be less than the entire length of the clamp meter.
When measuring on a high-voltage circuit, it is forbidden to use a wire to connect the clamp ammeter to another meter for measurement. When measuring the current of each phase of the high-voltage cable, the distance between the cable ends should be more than 300mm, and the insulation should be good, and the measurement can only be carried out when it is considered convenient.
When measuring the current of low-voltage fusible fuses or horizontally arranged low-voltage busbars, the fusible fuses or busbars of each phase should be protected and isolated with insulating materials before measurement, so as not to cause short circuits between phases
After the measurement of the clamp ammeter, pull the switch to the maximum range to avoid accidental overcurrent during the next use; and it should be stored in a dry room
It is strictly forbidden to measure when one phase of the cable is grounded. Prevent the occurrence of ground breakdown explosion due to the low insulation level of the cable head and endanger personal safety.
When using a high-voltage clamp meter, attention should be paid to the voltage level of the clamp meter, and it is strictly forbidden to use a low-voltage clamp meter to measure the current of the high-voltage circuit. When measuring with a high-voltage clamp meter, it should be operated by two people. Non-on-duty personnel should also fill in the first type of work ticket. When measuring, they should wear insulating gloves, stand on insulating mats, and do not touch other equipment to prevent short circuits or grounding.
How to use clamp ammeter:
First of all, correctly select the voltage level of the clamp ammeter, check whether its appearance insulation is good, whether it is damaged, whether the pointer swings flexibly, whether the jaw is rusted, etc. Estimate the rated current according to the motor power to select the range of the meter.
The jaws of the clamp meter should be closed tightly during measurement. If there is any noise after closing, you can open the jaws and repeat it again. If the noise still cannot be eliminated, you should check whether the joint surfaces on the magnetic circuit are smooth and clean, and wipe them clean if there is dust. .
The clamp meter can only measure the current of one phase wire at a time, and the wire to be tested should be placed in the center of the clamp window, and multi-phase wires cannot be clamped into the window for measurement.
The voltage of the circuit under test cannot exceed the value marked on the clamp meter, otherwise it may easily cause a grounding accident or cause an electric shock hazard.
Before using the clamp ammeter, you should read the instructions carefully to find out whether it is an AC or AC-DC dual-purpose clamp meter.
Due to the low accuracy of the clamp ammeter itself, the following method can be used when measuring small currents: first wind the wire of the circuit under test several times, and then put it into the jaw of the clamp meter for measurement. At this time, the current value indicated by the clamp meter is not the actual value being measured. The actual current should be the reading of the clamp meter divided by the number of turns of the wire.
Measure the operating current of the cage-type asynchronous motor in operation. According to the magnitude of the current, it can be checked to determine whether the motor is working normally, so as to ensure the safe operation of the motor and prolong its service life.
When measuring, it can be measured once for each phase or once for three phases. At this time, the number on the meter should be zero (because the phasor sum of the three-phase current is zero). When there are two phase wires in the jaw, the meter will display The value is the current value of the third phase. By measuring the current of each phase, it can be judged whether the motor is overloaded (the measured current exceeds the rated current value). Is there a problem, that is, whether the three-phase current imbalance exceeds the limit of 10%.
