Best Insulation Resistance Testers (Megohmmeters) in 2026
An insulation resistance tester — often called a megohmmeter or “megger” — checks whether the insulation of cables, motors, and equipment is safe and free from degradation. This complete guide explains test voltages, key features, and compares the real Marmonix insulation tester models so you can choose the best megohmmeter in 2026.
How an Insulation Tester Works
It applies a high DC test voltage across insulation and measures the resulting resistance in megohms (or up to teraohms). Low or falling readings reveal moisture, ageing, or damage long before they cause faults.
Key Features to Compare
- Test voltages (250V up to 10kV for HV equipment).
- Resistance range (up to 10–20 TΩ on advanced models).
- Diagnostic modes: PI, DAR, RAMP, FR.
- Safety: auto-discharge and live-circuit monitoring.
Marmonix Insulation Testers Compared
| Model | Test voltage | Range | Highlights | Best for |
|---|---|---|---|---|
| MIR 1000 | 100V–1000V | — | ±0.5%, insulation+continuity+voltage, data hold | General LV electrical |
| MIR 510 | 250V–5000V | 0.5MΩ–10TΩ | Colour touch screen, IP65, auto-discharge | MV equipment, field use |
| MIR 1020 | 250V–10kV | 0.5MΩ–20TΩ | PI, DAR, RAMP, FR tests, auto-discharge | HV diagnostics |
Model Strengths
MIR 1000 — compact 100V–1000V tester with ±0.5% accuracy plus continuity and voltage; ideal for general low-voltage work. MIR 510 — 5kV output, 10TΩ range, colour touch screen, and IP65 ruggedness for medium-voltage field testing. MIR 1020 — up to 10kV and 20TΩ with PI, DAR, RAMP, and Filtered-Resistance diagnostics for high-voltage work. Compare all Marmonix insulation testers.