Principle of operation and safety measures for clamp meters
The clamp meter is an instrument that combines an ammeter and a current transformer, and it operates on the same principles as a current transformer to measure current. A clamp meter combines an ammeter with a current transformer. When the wrench is tightened, the iron core of the current transformer can be opened, allowing the wire carrying the measured current to pass through the gap without being severed. When the wrench is loosened, the iron core closes.The measured circuit wire that passes through the iron core transforms into the primary coil of the current transformer, and the passage of the current induces current in the secondary coil. Measure the current flowing through the line being tested so that the ammeter attached to the secondary coil can display a reading.
By changing the gear of the switch, the clamp meter's ranges can be adjusted. However, using power while changing gears is prohibited. The clamp meter's accuracy is typically between 2.5 and 5, which is not very high. The meter has switches with various ranges for the functions of measuring voltage and different levels of current for ease of use.
Originally intended to measure AC current, the clamp meter today performs the same tasks as a multimeter, including measuring AC and DC voltage, current, capacitance, diode, transistor, resistance, temperature, frequency, and other variables.
How to use the clamp meter
(1) Mechanical zero adjustment is required before measurement
(2) Select the appropriate range, choose the large range first, and then select the small range or see the nameplate value for estimation.
(3) When the minimum range is used to measure and the reading is not significant, the measured wire can be wound for several turns, and the number of turns should be based on the number of turns in the center of the jaw, then the reading = indicated value × range / full deviation × turns number
(4) After the measurement is completed, the switch should be placed at the maximum range.
(5) When measuring, the wire under test should be in the center of the jaws, and the jaws should be closed tightly to reduce errors.
Clamp Meter Precautions
(1) The voltage of the line under test should be lower than the rated voltage of the clamp meter.
(2) When measuring the current of a high-voltage line, wear insulating gloves, wear insulating shoes, and stand on an insulating mat.
(3) The jaws should be closed tightly and the range cannot be changed with electricity
How to use the electrician to measure the clamp meter and matters needing attention
Clamp ammeters are divided into high and low voltage, which are used to directly measure the current in the line without disconnecting the line. Its usage is as follows:
(1) When using a high-voltage clamp meter, attention should be paid to the voltage level of the clamp ammeter, 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-duty personnel should also fill in the second type of work ticket when measuring. They should wear insulating gloves when measuring, stand on insulating mats, and do not touch other equipment to prevent short circuit or grounding.
(2) When observing the timing of the watch, special attention should be paid to maintaining a safe distance between the head and the live part. The distance between any part of the human body and the live body should not be less than the entire length of the clamp meter.
(3) When measuring on a high-voltage circuit, it is forbidden to use wires 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. The measurement can only be carried out when the measurement is convenient.
(4) 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 to avoid short-circuit between phases.
(5) It is strictly forbidden to measure when one phase of the cable is grounded. Prevent personal safety from being endangered due to ground breakdown explosion due to low insulation level of the cable head.
(6) Pull the switch to the maximum range after the measurement of the clamp ammeter to avoid accidental overcurrent during the next use; and keep it in a dry room
