UNI-T insulation tester (megger) guide
An insulation resistance tester ("megger") applies a DC test voltage and measures leakage through the insulation in MΩ or GΩ. The rule of thumb is to test at roughly the working voltage of the equipment, so the test voltage is the first thing to choose.
Which test voltage?
- 250 / 500 V — control wiring, 230 V appliances, small motors and low-voltage cables.
- 1000 V — 415 V motors, LT cables, panels and PV strings. The UT501A (up to 5 GΩ) is the standard contractor's tester; the UT505A / UT505B add data storage, PI/DAR and 20 GΩ range.
- 2500 V — HT motors and 3.3 / 6.6 kV cables: UT502A (20 GΩ, PI, DAR).
- 5000 V — 11 kV and above, transformers and generators: UT513A (1000 GΩ, data storage, auto discharge).
UT501AInsulation Resistance Tester₹5,460 incl. GSTIn stock
UT505AHandheld Insulstion Resistance Tester₹13,450 incl. GST
UT505BHandheld Insulstion Resistance Tester₹21,240 incl. GST
UT502AInsulation Resistance Tester₹8,836 incl. GSTIn stock
UT513AHigh Voltage Insulation Resistance Tester₹25,700 incl. GSTIn stock
UT503PVPV Insulation tester₹25,403 incl. GSTIn stock| Model | Test voltage | Max resistance | PI / DAR | Data storage | Price |
|---|---|---|---|---|---|
| UT501A | 1000V | 5GΩ | — | — | ₹5,460 |
| UT505A out of stock | — | — | — | — | ₹13,450 |
| UT505B out of stock | 1000V | 20GΩ | — | Yes | ₹21,240 |
| UT502A | 2500V | 20GΩ | Yes | — | ₹8,836 |
| UT513A | 5000V | 1000GΩ | — | Yes | ₹25,700 |
| UT503PV | 500V | 4GΩ | — | — | ₹25,403 |
PI and DAR — why they matter
A single MΩ reading depends on temperature and humidity. The Polarisation Index (10-min / 1-min reading) and Dielectric Absorption Ratio (60 s / 30 s) cancel most of that out: PI above 2 is healthy insulation, below 1 means moisture or contamination. Testers with PI/DAR (UT502A, UT505B, UT513A) do the timing for you.
Solar installers
The UT503PV is built for PV: 500–1000 V test voltage, 1000 V DC voltage measurement, a compare function against your pass limit, and timed tests — everything the IEC 62446 commissioning checklist asks for.
Installation testers
If you also need loop impedance and RCD trip-time testing for building certification, the UT526 multifunction installation tester combines insulation (250/500/1000 V), loop, RCD and voltage in one box.
UT526Muitifunction Electric Meter₹14,974 incl. GSTIn stock
UT501EFast Insulation Resistance tester₹16,737 incl. GSTIn stock