What's the Difference Between the Principle of Measuring Resistance with a Megohmmeter and That with a Multimeter?
A megohmmeter, also known as a shaking table, is mainly used to measure the insulation resistance of electrical equipment. It is composed of components such as the voltage doubling rectifier circuit of the AC generator and the meter head. When the shaking table is shaken, a direct current voltage is generated. When a certain voltage is applied to the insulation material, an extremely weak current will flow through it, which is composed of three parts: capacitive current, absorption current, and leakage current. The ratio of the DC voltage generated by a shaking table to the leakage current is called the insulation resistance test. The test of using a shaking table to check whether the insulation material is qualified is called the insulation resistance test. It can detect whether the insulation material is damp, damaged, or aged, thereby discovering equipment defects. The rated voltage of a megohmmeter is 250, 500, 1000, 2500V, etc., and the measurement range is 500, 1000, 2000M Ω, etc
The insulation resistance tester is also known as a megohmmeter, megohmmeter, or megohmmeter. The insulation resistance meter mainly consists of three parts. It is a DC high voltage generator used to generate a DC high voltage. **It's a measurement circuit. The third is display.
(1) DC high voltage generator
To measure insulation resistance, a high voltage must be applied at the measuring end, which is specified in the national standard for insulation resistance meters as 50V, 100V, 250V, 500V, 1000V, 2500V, 5000V
There are generally three methods for generating high DC voltage. **Type of hand cranked generator. At present, about 80% of the megohmmeters produced in China use this method (the name of the shaking meter comes from). **The method is to increase the voltage through a mains transformer and rectify it to obtain high DC voltage. The method commonly used for a commercial megohmmeter. The third method is to use transistor oscillation or dedicated pulse width modulation circuits to generate DC high voltage, which is commonly used in battery type and mains type insulation resistance meters.
