Megohmmeter Digital

Megohmmeters are instruments used to measure electrical resistance of insulators. They are referred to as insulation resistance meters or meggers.

The purpose of measuring resistance is to find any breaks or faults in the insulation. Breaks and faults create hazardous situations that may lead to equipment damage, electrical shock, or even death.

The acceptable or “safe” range of insulation resistance readings is between 1 to 10 megohms - which indicate good integrity of cable insulation.

As electrical systems and cables degrade with time, so does the quality of the insulation. Atmospheric conditions such as temperature, moisture, or dust particles are the most common factors contributing to lowering the quality and integrity of an electrical system.

The meter generates high DC voltage during a so called stress test. Typically, voltages of 250, 500 or 1000 volts are used for most of the common wires on low voltage systems. Voltages up to 5000 V are used in an industrial environment, as the cable grade is higher in these high voltage systems.

When voltage is applied to a conductor it will cause a certain amount of current to flow through it. The amount of current is related to voltage applied, as well as system capacitance, resistance and temperature of the material used. The stress test demonstrates if there are any breaks or faults in cables.

In the US there are several manufacturers who make quality meggers. They include, but are not limited to:

AEMC, Amprobe, Extech, Flir, Fluke, General Tools, Greenlee, Ideal Industries, Klein Tools.

It is important to purchase tools from reputable manufacturers, as they implement stringent quality control in their manufacturing process. When you work with electricity, you need to make sure all risk factors are eliminated.