The test voltage must match the circuit, not the other way round
An insulation tester applies a known direct voltage — commonly 250 V, 500 V or 1000 V — and measures the resistance that flows across it, in megohms. The selectable test voltage is the specification that decides whether the instrument suits the circuits you work on, because applying too high a voltage to sensitive equipment damages it. Most also do low-resistance continuity. We compare available test voltages, resistance range, continuity testing, the stated measurement category, and automatic discharge after a test.
Insulation resistance · multiple ranges · manual selection · backlit LCD
The entry point into insulation testing: a megohmmeter with several selectable ranges, manual measurement modes and a large backlit display.
Best for: Learning what an insulation test looks like, on equipment that is disconnected and safe to experiment on.
125 / 250 / 500 / 1000 V test · 0–4000 MΩ · CAT III 1000 V · dual display
Four selectable test voltages from 125 to 1000 V, insulation measurement to 4000 MΩ, continuity, AC and DC voltage — and a stated CAT III 1000 V rating.
Best for: Installation work where the test voltage has to match the circuit and the category has to be known.
50 / 100 / 250 / 500 / 1000 V · insulation to 20 GΩ · resistance 0.01 Ω–20 kΩ
Five test voltages from 50 to 1000 V and an insulation range reaching 20 GΩ — five times the ceiling of the PeakTech — with low-resistance measurement from 0.01 Ω.
Best for: Testing across a wide span of equipment, from electronics at 50 V to fixed wiring at 1000 V.
500 and 1000 V test · 600 MΩ · combined insulation tester and multimeter
A combined insulation tester and digital multimeter with 500 V and 1000 V test voltages and a 600 MΩ range, at the top of this hub by a factor of four.
Best for: Carrying one instrument instead of two, in a trade where that trade-off is worth the price.
≈ $799
The insulation test voltage depends on the nominal voltage of the circuit being checked. An instrument that does not offer it does not allow the expected test.
An instrument that tops out at twenty megohms cannot tell good insulation from excellent. The stated resistance range decides what the measurement allows you to conclude.
An insulation test leaves a charge on a long cable, and discharging is a safety step. A stated automatic discharge function is what protects the next person to touch it.
Imperatively, and the installation locked off. The insulation measurement is made dead, never otherwise.
Yes: the test voltage can destroy electronics left connected. The most expensive mistake of this test.
It depends on the circuit's nominal voltage and is set out in the applicable standards. Not a setting to guess at.
The thresholds are set by the standards in force according to the type of circuit. A raw value cannot be judged without that reference.
No. The instrument applies a high DC voltage, incompatible with an installation under voltage.
It gets you out of trouble. Dedicated instruments offer the standard voltages and a measurement more stable over time.
It signals a degradation that is a matter for a professional. Measuring it does not say where the fault is or how to treat it.
No: the test applies a high direct voltage and assumes a circuit that is dead and disconnected. Serious instruments refuse to start if they detect voltage, and that is a function worth looking for.
The measurement is made dead and locked off, with appliances disconnected: the test voltage destroys electronics left connected. The voltage applied and the acceptable threshold come from the standards, not from judgment — and low insulation is a matter for a professional.
A column is raised only if four instruments in five publish the value. Below that, it would be measuring the silence of the manuals.
| Model | Price | Insulation test |
|---|---|---|
| Fluke 1577 | $799 | 500 and 1000 V test · combined insulation tester and multimeter |
| GOYERRNES GR-VC60B+ | — | Insulation resistance |
| PeakTech P 2695 | — | 125 / 250 / 500 / 1000 V test |
| Voltcraft ET-200 | — | 50 / 100 / 250 / 500 / 1000 V · insulation to 20 GΩ |
Specifications: manufacturer sheets for measuring instruments and the matching Amazon product pages. Prices and availability: Keepa. Every figure in this table names its source.
Most recent revision in this category: August 31, 2026.
Prices quoted in these summaries are dated readings. The live price is shown next to each product.
