Insulation Tester

What is an Insulation Tester?

An insulation tester (also called a megger or megohmmeter) is a device that applies a high DC voltage to electrical equipment and measures resistance in megaohms (MΩ) or gigaohms (GΩ). Higher readings indicate better insulation health.

Why is insulation resistance testing important?

Insulation resistance testing helps detect deterioration caused by moisture, heat, aging, dust and contamination. Regular testing prevents electric shock hazards, equipment breakdown, fire risks and costly downtime.

Where are insulation testers used?

Insulation testers are widely used for:

• Motor and generator insulation testing
• Transformer winding resistance checks
• Power cable commissioning
• Switchgear and control panel maintenance
• Industrial plant electrical audits

What test voltages are available?

Common insulation test voltages include:

• 250V / 500V – Domestic and low voltage applications
• 1KV – Industrial panels and motors
• 5KV – High voltage equipment
• 10KV & above – Heavy industrial and utility applications

What is a good insulation resistance value?

As a general rule, insulation resistance should be at least 1 MΩ per kV of operating voltage. However, acceptable values depend on equipment type and industry standards.

What is PI and DAR in insulation testing?

Advanced digital insulation testers measure:

• Polarization Index (PI) – Indicates long-term insulation condition
• Dielectric Absorption Ratio (DAR) – Evaluates insulation moisture content

Safety precautions before testing

Always ensure the equipment is completely de-energized and discharged before testing. Never perform insulation testing on live circuits. Follow lockout/tagout procedures for safe operation.

How to choose the right insulation tester?

Select a tester based on required voltage range, testing environment, safety category (CAT rating), data logging needs and application type (motor, transformer, cable or panel testing).

Visit our offline store:
Industrial Supply Syndicate
54, Ezra Street, Kolkata – 700001
Phone: 8961089611
Email: info@indiameters.in

Buy high-quality digital insulation testers online in India with warranty and technical support from IndiaMeters.