How to calibrate a clamp ammeter
Measuring instruments commonly used by electricians include megometers, multimeters and clamp-type ammeters. If these instruments are not used correctly or are slightly negligent during measurement, the meter may be burned out, the component being measured may be damaged, and personal safety may even be endangered. Therefore, it is very important to master the correct use of commonly used electrical measuring instruments.
Megohmmeter Megohmmeter, also known as megohmmeter, is used to test the insulation condition of circuits or electrical equipment. The usage and precautions are as follows:
(1) First, select a megometer that is suitable for the voltage level of the component under test. For lines or electrical equipment of 500V and below, a 500V or 1000V megometer 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 megohmmeter, two people should do it.
(3) Before measurement, the power supply of the circuit or electrical equipment under test must be completely disconnected, that is, it is not allowed to measure the insulation resistance while the power is on. And make sure no one is working on the wiring or electrical equipment before proceeding.
(4) The meter wire used by the megohmmeter must be an insulated wire, and double-stranded insulated wire should not be used. The end of the meter wire should have an insulating sheath; the line terminal "L" of the megohmmeter should be connected to the device under test. phase, the ground 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 protective ring or cable insulation sheath to reduce the measurement error caused by leakage current on the insulation surface.
(5) The megohmmeter should be checked for open circuit before measurement. When the "L" end and "E" end of the megohmmeter are unloaded, the pointer of the shaker should point to "∞" when the "L" end and "E" end of the megometer are short-circuited. When the shaker is shaken, the pointer should point to "0". ". It indicates that the megohmmeter functions well and can be used.
(6) The circuit or electrical equipment under test must be grounded and discharged before testing. When testing a line, you must obtain permission from the other party before proceeding.
(7) When measuring, the speed of shaking the handle of the rocker should be uniformly 120r/min; after maintaining a stable speed for 1 minute, take the reading to avoid the influence of absorbed current.
(8) During the test, both hands are not allowed to touch the two wires at the same time.
(9) After the test is completed, the stitches should be removed first and then stop shaking the watch. This is to prevent the electrical equipment from backcharging the megohmmeter and causing damage to the megohmmeter.
(10) During lightning, it is strictly prohibited to test the line insulation.
