Insulation Resistance Testers Compared: 3 Listings
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An insulation checker is a meter that applies a set test voltage and reports how well the insulation of a cable, winding or device holds back the current. This page compares three listings that name an insulation resistance tester or megohmmeter in their titles. It covers the stated test voltages, the resistance ceilings, the safety ratings, the included parts and the extra functions each listing names.
The three listings share a 250 V lowest test voltage and differ on everything above it. Each section below keeps the figures from one listing separate from the others. Listing data was checked on 2026-10-20.
Quick answer
The Fluke 1535 states the highest resistance figure in this group, up to 500 GΩ, and it states a CAT IV 600V rating with no CAT III figure beside it. The NJTY T6125 states a range from 0.01 MΩ to 200 GΩ with four test voltages, and it adds low resistance testing from 0.01 Ω to 60 Ω. The AOPUTTRIVER states the lowest resistance ceiling of the three, 200 MΩ at 250 V and 500 V and 2000 MΩ at 1000 V.
If you need a continuity buzzer, the AOPUTTRIVER listing is the one that states it, below 50 Ω. If you need automatic polarization index and dielectric absorption ratio calculations, the Fluke and NJTY listings both state them.
Comparison table
| Listing | Stated test voltages | Stated resistance ceiling | Safety rating | Included |
|---|---|---|---|---|
| NJTY T6125 digital insulation resistance tester, 2500V (first listing) | 250, 500, 1000 and 2500 V (bullets); AC voltage 10 to 600 V | 0.01 MΩ to 200 GΩ (title and bullets); low resistance 0.01 Ω to 60 Ω (bullets) | IEC 61010-1, CAT III 1000V, CAT IV 600V (specification field) | Eight AA batteries, silicone leads, alligator clips, bag, manual (highlight and specification field) |
| Fluke 1535 insulation tester (second listing) | 250 V to 2500 V (title) | Up to 500 GΩ (title) | CAT IV 600V (specification field and bullets) | Fluke 1535, TL1550B test lead set and carrying case (specification field) |
| AOPUTTRIVER megohmmeter 1000V (third listing) | 250, 500 and 1000 V (bullets); DC to 1000 V and AC to 750 V (bullets) | 200 MΩ at 250 V and 500 V; 2000 MΩ at 1000 V (bullets) | UL 61010-1, IEC 61010-2-030, CE (specification field) | Six AA batteries (bullets); manual (specification field) |
The first listing: NJTY T6125 digital insulation resistance tester
The listing names NJTY and model T6125, with a title that gives 2500 V and a range from 0.01 MΩ to 200 GΩ. Its specification fields give battery power, a minimum operating voltage of 10 volts, a maximum operating voltage of 2500 volts, a yellow color and a weight of 1.2 pounds. The measurement types listed are ammeter, LCR meter, multimeter, ohmmeter and voltmeter, and the dimensions are 3.7 x 1.68 x 6.3 inches.
The bullets describe four selectable output voltages, 250 V, 500 V, 1000 V and 2500 V, and say the tester measures AC voltage from 10 V to 600 V. They give low resistance testing from 0.01 Ω to 60 Ω, a data hold function, an over-range alarm and an automatic shutdown after inactivity. They describe a large LCD with gray-white backlighting, and a shockproof, dustproof and moisture-proof structure with a protective case.
- Test voltages: 250, 500, 1000 and 2500 V (bullets)
- Resistance: 0.01 MΩ to 200 GΩ (title and bullets)
- Low resistance: 0.01 Ω to 60 Ω (bullets)
- Safety: IEC 61010-1, CAT III 1000V, CAT IV 600V (specification field)
The listing includes eight AA batteries, silicone leads, alligator clips, a 5.5 mm plug, a bag and a manual, according to the highlight and specification fields. It is the only one of the three that also states a low resistance range.
The second listing: Fluke 1535 insulation tester
The listing names Fluke and model FLUKE-1535. Its title describes an insulation tester for industrial and electrical insulation testing, with test voltages from 250 V to 2500 V and resistance measurements up to 500 GΩ. The specification fields give battery power, a minimum operating voltage of 250 volts, a measurement type of ohmmeter, a style of safety, a yellow color and a weight of 6.07 pounds. The dimensions are 7.3 x 8.3 x 3.7 inches.
The bullets say the tester checks the integrity of cables, motor and transformer windings and other equipment. They state that it calculates the polarization index (PI) and dielectric absorption ratio (DAR) automatically, and that it has a fast measurement design for steadier resistance readings. They also state a voltage alarm and compliance with CAT IV 600V. The included components are the tester, a TL1550B test lead set and a carrying case.
- Test voltages: 250 V to 2500 V (title)
- Resistance: up to 500 GΩ (title)
- Functions: automatic PI and DAR calculation (bullets)
- Safety: CAT IV 600V (specification field and bullets); voltage alarm (bullets)
This listing gives the highest resistance ceiling of the three and the heaviest unit, at 6.07 pounds. It is the one to check if you need a carrying case and a listed test lead set in the same package.
The third listing: AOPUTTRIVER megohmmeter 1000V
The listing names AOPUTTRIVER and model “Megaohm Meter 1000V”. Its title describes a 1000V megohmmeter with AC voltage to 750 V. The specification fields give battery power, a minimum operating voltage of 250 volts DC, a measurement type of ohmmeter, a compact style and a weight of 1.28 pounds. The dimensions are 6.69 x 2.48 x 6.93 inches, and the listed color code is T6-VC60B-US.
The highlight field and bullets state test voltages of 250 V, 500 V and 1000 V, with DC voltage up to 1000 V and AC voltage up to 750 V. The bullets give insulation resistance up to 200 MΩ at 250 V and 500 V, and up to 2000 MΩ at 1000 V. They describe a resistance range up to 2 kΩ at ±(0.8%+6) accuracy, a continuity buzzer that sounds below 50 Ω, and a continuous test lock. The bullets also say the unit is powered by six AA batteries, which are included, and they give a size of 175 x 110 x 62.5 mm and a weight of 580 g.
- Test voltages: 250, 500 and 1000 V (highlight and bullets)
- Resistance: 200 MΩ at 250 V and 500 V; 2000 MΩ at 1000 V (bullets)
- Continuity: buzzer below 50 Ω; resistance up to 2 kΩ (bullets)
- Power: six AA batteries, included (bullets)
The specification field lists the included components as a manual only, while the bullets say the six batteries are included. Confirm which is correct on the product page before you rely on it.
How these three were chosen
Each listing above has a title that names an insulation resistance tester or megohmmeter. Other products in related results, including GFCI outlet testers, battery testers, automotive circuit testers and USB testers, are left out because they are not insulation testers. Figures come from each listing’s own fields and bullets, and all three were checked on 2026-10-20.
Worked example: the top reading in each listing
Take the highest stated reading in each listing. The Fluke states 500 GΩ, the NJTY states 200 GΩ and the AOPUTTRIVER states 2000 MΩ at 1000 V, which is 2 GΩ. The Fluke’s ceiling is 2.5 times the NJTY’s and 250 times the AOPUTTRIVER’s. Those ratios describe stated maximums only, and they are not a measure of how the instruments perform at those readings.
The test voltages for the same top figure also differ. The NJTY and Fluke both reach 2500 V on their stated range, while the AOPUTTRIVER stops at 1000 V. A reading taken at 1000 V on the AOPUTTRIVER therefore sits at the top of its stated test voltage span, not the middle of a wider set.
What the listings do not say
- The Fluke listing does not state the individual test voltages behind its 250 V to 2500 V span, so the steps between them are unknown.
- None of the three states an accuracy figure for its high-resistance readings, apart from the AOPUTTRIVER’s accuracy for its 2 kΩ resistance range.
- The AOPUTTRIVER specification field and its bullets disagree on included batteries.
- The NJTY listing does not state the battery type beyond the AA count.
- None of the three states a response time or a reading update rate.
Related buying guides
For a wider view of insulation work, the insulation resistance test equipment guide covers the broader group of testers, the insulation resistance tester guide covers the main models, and the megohmmeter tester guide covers meters with a megohm range.
FAQ
Which listing states the highest resistance ceiling?
The Fluke 1535 states up to 500 GΩ in its title. The NJTY states 200 GΩ and the AOPUTTRIVER states 2000 MΩ at 1000 V.
Which listing states a continuity buzzer?
The AOPUTTRIVER states a continuity buzzer that sounds below 50 Ω. The NJTY states low resistance testing from 0.01 Ω to 60 Ω, and the Fluke does not state a continuity function.
Which listings calculate PI and DAR?
The Fluke 1535 and the NJTY T6125 both state automatic PI and DAR functions. The AOPUTTRIVER does not state them in its listing text.
Do all three start at 250 V?
Yes. The NJTY lists 250 V as its lowest output, the Fluke title begins at 250 V, and the AOPUTTRIVER lists 250 V as its lowest test voltage.
What should I confirm before buying?
Confirm the test voltage you need and the resistance ceiling at that voltage, whether you need a continuity buzzer, and whether batteries are included with the unit you buy. Check the product page for each, since the AOPUTTRIVER listing disagrees with itself on batteries.
Bottom line
For the highest stated resistance and a carrying case, the Fluke 1535 is the strongest match on its own figures. The NJTY T6125 offers four test voltages, low resistance testing and a stated CAT IV 600V rating in one listing. The AOPUTTRIVER is the one with a stated continuity buzzer and a 1000 V top test voltage, with a conflict on included batteries. Pick by the resistance ceiling and test voltage your equipment needs, then confirm the rest on the product page.
