1 Introduction
Insulation resistance meter, also known as megameter, table, and Meg, the insulation resistance meter is mainly composed of three parts; The first is the dc high voltage generator to produce the dc high voltage; The second is to measure the special instrument used to measure the maximum resistance, insulation resistance, absorption ratio and polarization index. Its scale unit is megohm, which has a high voltage power supply. Loop; The third is display. A special instrument used to measure the maximum resistance, insulation resistance, absorption ratio and polarization index. Its scale unit is megohm, which has a high voltage power supply.

2 Structure and composition

(1)DC high voltage generator.

(2)Measuring circuit

In the table above, the measurement loop and the display part are one. Than it is to have a flow meter, to complete the meter in the header, there are two Angle 60 ° of coil (or so), is one of the coil and the voltage at both ends and the other coil is string in the measurement circuit. Header pointer deflection Angle is determined by the current ratio of the two coils, different represent different resistance, deflection Angle measuring resistance, the smaller the greater the string in the coil current measurement circuit, then the pointer deflection Angle is bigger. Another method is to use a linear ammeter as a measurement and display. Use than flow meter in front of the header because the coil in the magnetic field is uniform, when the pointer in the infinity, current coil is just where the strongest magnetic flux density, so despite the resistance being very high, being measured current flows through the coil current is small, the coil deflection Angle is bigger. When the measured resistance is small or 0, the current in the current coil is larger, and the coil is deflected to a place where the flux density is small, and the deflection Angle caused by this is not very large. So we have a nonlinear correction. Generally, the resistance of the meter header is several orders of magnitude. But when using linear current meter head string directly into the measuring circuit is washed-up, when high value scale of all crowded together, unable to distinguish, in order to also to achieve the nonlinear correction must be in the measurement circuit using nonlinear components. Thus, the shunt function is achieved when the small resistance value is obtained. There is no shunt in high resistance, which results in several orders of magnitude. With the development of electronic technology and computer technology, digital display table is gradually replacing pointer instrument.
The digital measurement technology of insulation resistance has also been developed, among which the voltage ratio meter circuit is one of the better measuring circuit, and the voltmeter circuit is composed of the voltage bridge circuit and the measuring bridge circuit. The signals output by these two Bridges are converted by A/D conversion and directly converted into digital values by single chip processing.
The insulation resistance meter is used to measure the voltage value, and the other is the range that needs to be measured to meet the needs. If measurement is very frequent, it is best to choose alarm setting function.