Insulation Resistance & Megohmmeters

Insulation resistance testers — commonly called megohmmeters or meggers — measure the resistance of electrical insulation in motors, cables, transformers, switchgear, and wiring systems. By applying a DC test voltage (typically 500 V to 15 kV) and measuring the resulting leakage current, these instruments calculate insulation resistance in megohms or gigohms, revealing deterioration, moisture ingress, contamination, or physical damage before failures occur.

Modern megohmmeters support advanced diagnostic tests including Polarization Index (PI), Dielectric Absorption Ratio (DAR), Step Voltage testing, and Dielectric Discharge analysis. These tests provide maintenance engineers with a comprehensive assessment of insulation health and support planned preventive maintenance programs in power utilities, industrial plants, and commercial facilities.

Typical Applications

Routine maintenance testing of electric motors and generators in industrial plants
Cable insulation testing for medium- and high-voltage distribution systems
Transformer acceptance and periodic maintenance testing in power utilities
Switchgear and panelboard insulation verification
Commissioning and acceptance testing of new electrical installations

Popular Brands

Megger is the industry-leading manufacturer of insulation resistance testers, offering instruments from portable 500 V handheld units to 15 kV diagnostic testers such as the S1-1568 series. Fluke, Hioki, and Kyoritsu also produce well-regarded megohmmeters suited to field maintenance, laboratory diagnostics, and high-voltage testing applications.