Tester. This instrument is suitable for measuring the insulation resistance of various transformers, motors, cables, switches, electrical equipment and insulation materials.
High voltage insulation resistance tester is commonly known as megohmmeter, or shaking table, high resistance meter, insulation resistance tester, etc. Insulation resistance meters are widely used in power websites and electrical equipment to detect insulation resistance, which is of great significance to ensure product quality and personal and equipment safety in operation. The insulation performance of electrical products is one of the important signs to evaluate its insulation quality, which is reflected by insulation resistance.
product mix
1, the high voltage insulation resistance tester is mainly composed of three parts.
The first one is a DC high voltage generator, which is used to generate DC high voltage.
The second is the measuring loop.
The third is to show.
(1) DC high voltage generator
In order to measure the insulation resistance, high voltage must be applied at the measuring end, which is specified as 50V, 100V, 250V, 500V, 1000V, 2500V, 5000V…
There are usually three ways to generate DC high voltage. The first kind of manual generator. At present, about 80% megohmmeters produced in China adopt this method (source of shaking table name). The second is to boost the voltage through the main transformer and rectify it to obtain DC high voltage. Methods adopted by general commercial megohmmeter. The third is profit.
The methods of generating DC high voltage by transistor oscillation or special pulse width modulation circuit generally include battery type and commercial power type insulation resistance meter.
(2) Measuring circuit
In the above-mentioned shaking table (megohmmeter), the measuring circuit and the display part are combined together.
For example. It is completed by the flowmeter head, which consists of two coils with an included angle of 60 (about 60), one of which is connected in parallel at both ends of the voltage, and the other is connected in series in the measuring circuit.
The deflection angle of the pointer on the meter head is determined by the current ratio in the two coils. Different deflection angles represent different resistance values. The smaller the measuring resistance, the larger the coil current in the measuring loop and the larger the pointer deflection angle. in addition
One method is to use linear ammeter as measurement and display. Because the magnetic field in the coil is uneven in the meter head of the ammeter used before, when the pointer is at infinity, the current coil is just where the magnetic flux density is the strongest, so although
The measured resistance is very large and the current flowing through the current coil is very small. At this time, the deflection angle of the coil will be large. When the measured resistance is small or zero, the current flowing through the current coil is very large, and the coil has been deflected to a place where the magnetic flux density is very small, which is determined by the following formula.
The deflection angle caused by this will not be very large. In this way, nonlinear correction is realized. Generally, the resistance display of megohmmeter header needs to span several orders of magnitude. But when the linear ammeter head is directly connected in series with the measuring circuit, it will not work.
The scales at the high resistance are crowded together and can't be distinguished. In order to realize nonlinear correction, nonlinear components must be added to the measuring circuit. So as to realize the shunt effect when the resistance value is small. Do not generate high resistance.
Shunt, make the resistance display reach several orders of magnitude. With the development of electronic technology and computer technology, digital display meter gradually replaces pointer instrument.
Digital measurement technology of insulation resistance has also been developed, among which voltage comparator circuit is one of the better measurement circuits, which consists of voltage bridge and measurement bridge. The signals output by these two bridges are converted into digital values by A/D respectively, and then displayed by single chip microcomputer.
Product alias:
Double display insulation resistance tester, high voltage insulation resistance tester, insulation resistance tester, digital megger, electronic megger, insulation meter, megger.