Insulation resistance tester

Insulation resistance tester, also known as digital insulation resistance tester, megohmmeter, intelligent insulation resistance tester, etc.



An electrical system is like a piping system, where voltage is like liquid pressure, current is like the flow rate of liquid, and electrical insulation is like the pipe wall. Insulation prevents electrons from leaking from conductors – its effectiveness is expressed by insulation resistance. An effective insulation resistance system has a high resistance value, usually greater than several megohms. A poor insulation system has lower insulation resistance.



2 Product Introduction

The intelligent dual-display insulation resistance tester (two ranges) adopts an embedded industrial microcontroller real-time operating system, perfectly combining an ultra-thin tension wire meter with a graphic dot matrix LCD. This series of testers has multiple voltage output levels (500V, 1000V, 2500V, 5000V), large capacity, strong anti-interference, synchronous pointer and digital display, AC/DC dual use, simple operation, automatic calculation of various insulation indicators (absorption ratio, polarization index), and various measurement results with power-off protection. This series of intelligent dual-display insulation resistance testers is an ideal testing instrument for measuring the insulation resistance of large-capacity transformers, transformers, generators, high-voltage motors, power capacitors, power cables, lightning arresters, etc.



3 Working Principle

  The insulation tester, commonly known as a megohmmeter or high resistance meter, is widely used to measure the insulation resistance of generators, motors, power transformers, wiring, electrical appliances, and other electrical devices (such as cables for control, signal, communication, and power). They are often used in routine maintenance procedures to indicate changes in insulation resistance of motors over months or years. A large change in insulation resistance may indicate a potential fault. Therefore, it is necessary to calibrate the megohmmeter regularly to ensure that the instrument itself has not changed over time.



        The megohmmeter measures resistance by applying a voltage to excite the device under test or network, then measuring the current generated by the excitation, and using Ohm's law to calculate the resistance. A good megohmmeter calibrator includes various selectable resistors, which is not much different from modern calibrators that use synthetic resistance functions to provide resistors. The difference between a megohmmeter calibrator and a DC/low-frequency calibrator lies in the range of resistors required and the voltage withstand capability. For example, compared to the ohmmeter function on a digital multimeter (DMM), these electrical testers apply much higher voltages when measuring resistance. Megohmmeters typically use voltage ranges from 50V up to 5 kV; while typical digital multimeters use voltages generally less than 10 V. For insulation testing, the resistance values to be measured range widely, with an upper limit up to 10TΩ, requiring higher voltages.