Extech MG310 Digital Insulation Tester

The Extech MG310 is engineered for field and workshop use, offering a balance of portability and performance for insulation testing. It supports three selectable insulation test voltages (250 V, 500 V, 1000 V) and automatically ranges insulation resistance from 0 Ω up to 5.5 GΩ. A built-in Polarization Index (PI) mode and Dielectric Absorption Ratio (DAR) testing allow users to assess insulation quality over time and detect latent insulation degradation.

When not performing insulation tests, the MG310 functions as a standard electrical tester. It measures AC voltage from 30 to 600 V, checks continuity with beeper and zero offset (for low resistance), and handles resistance measurements up to 200 Ω. Safety features include an auto-discharge mechanism to safely bleed test voltage after execution, and overload/high-voltage warnings. The unit is rated CAT III 600 V, suitable for most distribution-level applications. It ships with test leads, alligator clips, six AA batteries, a hard snap-on cover, and a soft carry pouch.

Features

• Insulation Test Voltages — 250 V, 500 V, and 1000 V selectable
• High Insulation Range — Up to 5.5 GΩ auto-ranging
• PI & DAR Testing — Polarization Index and Dielectric Absorption Ratio modes for insulation quality evaluation
• AC Voltage Measurement — 30 to 600 V range
• Continuity & Low Resistance — Beeper, zero function for small resistance measurements
• Auto-Discharge & Warnings — Discharges residual voltage and flags overvoltage or overload conditions
• Safety Rating — CAT III 600 V
• Display & Interface — Large dual 2000-count backlit display
• Portability — Compact with included protective cover and carry pouch
• Complete Kit — Comes with test leads, alligator clips, batteries, cover, pouch

Includes

• Test leads
• Alligator clips
• 6 x AA batteries
• Hard cover,
• Soft carrying case