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What is a megohm meter

time:2020/6/17   source:华天电力  reading:291 time

Megometer or megometer is an electrical test instrument designed to test extremely high resistance by generating a DC (direct current) voltage of 300 to 15,000 volts. Megometers generate high voltage, low current DC charges, allowing you to test the resistance normally encountered in motor windings or cable insulation tests. Megometers generate this high voltage either through battery-powered internal circuits or manually operated generators.


Due to the extremely high resistance common in these applications, the use of conventional ohmmeters to test the windings, ground or insulation resistance of electrical equipment, machinery or devices may not be accurately realized. In these cases, the resistance may range from a few megoyles to several million megoyles, and the required test voltage is much higher than that used by the smaller ohmmeter. Megom meters use dc voltages of 300 to 15,000 volts to accurately measure these very high resistances. These voltages are provided at very low rated current and are generally not dangerous to Megabyte users.


Insulation Resistance Tester.png


There are two basic types of megometers: one is battery-powered, and the other is powered by a crank or an electric generator. Both megohm models allow accurate insulation resistance testing on installations and equipment with resistance of several megohm (1,000,000 megohm). The battery-powered megom USES a special internal circuit to convert the battery's low voltage to a higher test voltage. These instruments are usually smaller and lighter than generator versions, and have the advantage of single-key operation, one-handed operation, and a variety of operating voltages to choose from. The disadvantage of battery megometers is that they have a short battery life, usually producing a maximum voltage of 5,000 volts.


The generator megohm meter relies on a small internal generator to generate the required high test voltage. These generators are usually operated manually with an external crank handle, but internal motor drivers can be installed. These devices can produce voltages of 300 to 15,000 volts without the need to replace batteries. A disadvantage of using this instrument is that the operation requires two hands and therefore requires the use of clip leads or the help of a second person. They are also usually bulky and provide a single test voltage.


When testing electrical equipment, always keep in mind the high voltage generated by these instruments. The test voltage of the dynamometer should not exceed the operating voltage margin of the equipment under test, or irreversible damage may result. Although the test voltage is provided at very low amperes, care should always be taken to prevent electric shocks when working with megometers.


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