10 Steps to Calibrate a Clamp Meter
Measuring instruments commonly used by electricians include shaker meters, multimeters, and clamp ammeters. If these instruments are not used correctly or are slightly negligent during measurement, the meter will either be burned out, or the components under test will be damaged, and even personal safety will be endangered. Therefore, it is very important to master the correct use of commonly used electrical measuring instruments.
Megger Megger, also known as megohmmeter, is used to test the insulation condition of lines or electrical equipment. The usage and precautions are as follows:
(1) First, select a megger suitable for the voltage level of the component under test. For lines or electrical equipment of 500V and below, a 500V or 1000V megger should be used. For lines or electrical equipment above 500V, a 1000V or 2500V megger should be used.
(2) When testing the insulation of high-voltage equipment with a megger, it should be carried out by two people.
(3) Before the measurement, the power supply of the tested circuit or electrical equipment must be completely disconnected, that is, it is not allowed to measure the insulation resistance with power on. And it can only be carried out after confirming that no one is working on the line or electrical equipment.
(4) The meter wire used by the meter must be insulated wire, and it is not suitable to use twisted insulated wire. The end of the meter wire should have an insulating sheath; the line terminal "L" of the meter should be connected to the device under test. The grounding terminal "E" should be connected to the equipment shell and the non-measured phase of the equipment, and the shielding terminal "G" should be connected to the protection ring or the cable insulation sheath to reduce the error caused by the leakage current on the insulation surface.
(5) The megger should be checked for open circuit before measurement. When the "L" end and "E" end of the shaker meter are empty, shake the shaker meter, and its pointer should point to "∞"; ". It means that the shaker function is good and can be used.
(6) Before testing, the tested circuit or electrical equipment must be grounded and discharged. When testing the line, you must obtain the permission of the other party before proceeding.
(7) When measuring, it is advisable to shake the handle at a uniform speed of 120r/min; after maintaining a stable speed for 1min, take the reading to avoid the influence of the absorbed current.
(8) During the test, both hands shall not touch the two wires at the same time.
(9) After the test, the stitches should be removed first, and then stop shaking the watch. In order to prevent electrical equipment from reversely charging the megger and causing damage to the megger.
(10) During lightning, it is strictly forbidden to test the line insulation.
