Best High Voltage Megger: Three Insulation Resistance Testers Compared

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A high voltage megger is an insulation resistance tester. It applies a DC test voltage across cable, motor winding, transformer or switchgear insulation and reads the leakage resistance in megohms or gigohms. The person typing “high voltage megger” usually wants one instrument that can apply a test voltage of 2,500 V or more and report the result in a usable range. This guide compares the three insulation testers in our research set that meet that description. It also explains why four other items from the same search were removed.

Quick answer

Choose the highest test voltage your equipment needs, not the highest a listing shows. Fluke Learn notes that some handheld testers supply only up to 1,000 V DC while others supply 5,000 V DC or more.
The ETCR3500B lists the widest voltage set in this group, up to 10 kV, plus polarization index, DAR, step and ramp tests.
The GOLDCHAMP GCCA-6688B lists 5,000 V and a 200 GΩ range, and adds an AC voltmeter function.
The PEAKMETER EC-MS5205 lists a 2,500 V maximum and a 100 GΩ range, with automatic PI and DAR calculation.
Only test de-energized circuits. The test voltage can damage the equipment connected to the circuit under test.

What a high voltage megger measures

An insulation resistance test checks how well insulation keeps current from leaking through it. The tester applies a known DC voltage and measures the very small current that flows. Resistance is then calculated from the voltage and the current. The Tektronix application note on leakage current and insulation resistance states that insulation resistance measurements are returned in units of ohms, so a result in megohms or gigohms is simply a larger number of the same quantity.

Fluke Learn describes insulation testers as instruments that apply a test voltage and measure insulation resistance in megohms or gigohms. Its article “Improve uptime by sharing insulation resistance test data” makes a point that matters for any buyer: both voltage and temperature are not steady during a test, so both must be compensated before a result can be compared with an earlier one. A tester that stores test voltage and temperature with each reading is therefore more useful than one that stores only the resistance value.

The same article says Fluke’s insulation resistance testers calculate the polarization index (PI) and the dielectric absorption ratio (DAR) automatically. The Fluke guide “Guide to Insulation Resistance Testing” describes PI as a ratio of a 10-minute reading to a 1-minute reading. DAR is a shorter ratio, based on readings at 60 seconds and 30 seconds. Both ratios look at how the reading changes over time, so they can reveal moisture or contamination that a single reading may hide. Several of the testers below list PI and DAR as functions.

How to choose a test voltage

The test voltage is the most important setting on a high voltage megger, and the right value depends on the equipment rating. Fluke Learn’s article “Insulation Tester vs Megohmmeter” recommends basing the voltage on the manufacturer’s specification for the equipment. It also gives a set of minimum test voltages attributed to NETA practice: 500 V DC for 250 V equipment, 1,000 V DC for 600 V and 1,000 V equipment, and 2,500 V DC for 5,000 V and 15,000 V equipment. These are minimums to start from, not a substitute for the equipment’s own test specification.

Two practical points follow from this. First, a higher voltage does not automatically give a better answer. A tester that can reach 10 kV can still be set to 500 V for a low-voltage motor. Second, the tester’s own voltage range should cover the highest voltage you expect to use, because a test at 2,500 V cannot be run on a tester whose top setting is 1,000 V.

Test voltage is also a safety question. The Tektronix application note describes insulation resistance as a measurement that must be made on a circuit that is isolated from its supply. A higher test voltage increases the energy in the test circuit, so the equipment’s rating and the tester’s own category rating should both be checked before the leads are connected.

How to read the results

A single reading is a snapshot. The reading depends on the test voltage, the test duration and the temperature when it was taken. Fluke’s guidance is to record the test voltage and temperature with each result, and to compare new readings with earlier readings from the same equipment at the same settings. A drop from one test to the next, even when the value is still high, can be more informative than the absolute number.

Polarization index is the most common ratio for rotating machines. Healthy insulation usually shows a rising resistance over the 10-minute test, because the charging and absorption currents decay. A flat curve can point to moisture or oil contamination. The same logic applies to DAR, which is a faster check. Because the calculation is easy to get wrong by hand, a tester that calculates PI and DAR automatically, such as the PEAKMETER EC-MS5205 and the ETCR3500B listings describe, removes one source of error from the procedure.

Resistance also varies with temperature and humidity. The Fluke article on sharing test data lists temperature compensation as a stored value that should be recorded with each test. Readings taken at very different temperatures should be corrected before they are compared. Our sources do not give a single correction factor that applies to every insulation type, so use the equipment manufacturer’s data for correction when it is available.

Safety and procedure

Insulation testing is done on equipment that is de-energized, locked out and tagged out. The Fluke Learn article on sequential insulation resistance tests says that tests should be run only after lockout and tagout, with the circuit de-energized. It also notes that electronic controls and other devices connected to the circuit should be isolated first, because the test voltage can damage them. A motor should not be returned to service until the insulation has been checked for a short to ground.

The Klein Tools ET600 and Keysight insulation tester material we looked for could not be read in the sources we opened, so this section relies on the Fluke articles. Those sources repeat the same basic rule: confirm the circuit has no live voltage before the test starts, and treat the equipment as charged after the test. Capacitive loads hold a charge after the test. Several listings in this group include an automatic discharge function, which is useful, but it does not remove the need to discharge the equipment with the leads still connected.

Use the tester’s own live-voltage check if it has one. The ETCR3500B listing says it measures live voltage and prohibits testing when the measured voltage exceeds 36 V. That is a helpful interlock, but it is a feature of that model, not a substitute for isolating the circuit.

Why four items were removed from the list

The search for this keyword returned seven listings. Four of them are not insulation resistance testers, so they are not compared here.

Fluke 80K-40 High Voltage Probe (B000LDQ672): a voltmeter probe. Its listing describes it as a hand-powered accessory for a voltmeter. It has no test voltage source, so it cannot measure insulation resistance.
Fluke 80K-6 High Voltage Probe (B000LDCP4U): a voltmeter probe that extends measuring capability to 6,000 V peak. Its listing states that it requires a voltmeter with at least 10 megohm input resistance. It measures voltage only.
HVP-40 High Voltage Probe (B0H9QG5WD4): a 1000:1 divider probe for a digital multimeter. Its listing gives ZIBOO as the manufacturer. It measures voltage and is not a megger.
Klein Tools HVNCVT-1 Dual-Range Non-Contact High-Voltage Tester (B015KU2EXU): a non-contact voltage detector. Its listing describes audible and visual signals that indicate the presence of voltage. It does not measure insulation resistance.

How we chose

We kept an item only if its listing describes a device that applies a DC test voltage and reports insulation resistance. We then compared the three remaining testers on four points that the listings state directly: the set of test voltages, the resistance range, the calculated ratios (PI and DAR), and the storage or interface features. We did not rank the testers by price, rating or sales data, and we did not use customer review counts. Where a listing did not state a value, we say so below rather than filling the gap.

The three testers compared

1. ETCR3500B 10 kV High Voltage Insulation Tester (ETCR)

This is the highest-voltage unit in the group. The listing gives rated voltages of 50 V, 250 V, 500 V, 1,000 V, 2,500 V, 5,000 V and 10 kV. The insulation resistance range is listed as 0.005 MΩ to 10.00 TΩ, and the short-circuit current is listed as 5 mA maximum. The listing also gives a custom output voltage setting from 40 V to 10 kV and a custom test time from 10 s to 3,600 s.

Its listed functions include polarization index, DAR, step voltage and ramp tests. The unit stores 1,000 groups of test data with date and time, and the listing says the records can be uploaded to a computer over USB. The host is battery powered, and the listing gives an IP65 rating for the closed case and IP40 with the case open. The listed host weight is 3,344 g, and the total weight with all accessories is 5.6 kg. The listed safety standards are IEC 61010-1 and IEC 61326-1. A temperature and humidity monitor and a real-time current display are also listed.

The listing says the tester is designed for long cables and for electromagnetically noisy sites such as substations. These are manufacturer statements. We could not confirm them with an independent source, so they are listed under what we could not verify.

2. GOLDCHAMP Digital Megohmmeter GCCA-6688B (GOLDCHAMP)

This is a battery-powered megohmmeter with selectable output voltages of 100 V, 250 V, 500 V, 1,000 V, 2,500 V and 5,000 V. The listing gives a resistance range of 0.1 MΩ to 200 GΩ with auto-ranging, an accuracy of 3% to 10% plus 5 digits, and an approximate short-circuit output current of 1 mA.

The unit also works as an AC true-RMS voltmeter from 1 V to 750 V, with a listed frequency range of 40 Hz to 400 Hz. It has a backlit 1,999-count display and a data hold function. A built-in shield terminal (COM) is listed as a way to reduce surface-leakage errors. The listing refers to IEC-1010 double insulation and an overvoltage category II rating, and it describes a high-voltage LED warning that flashes during output. The TEST/STOP button is listed as stopping the output immediately, followed by automatic discharge of capacitive residual charge. The listing states a one-year quality assurance period.

Two points need checking before purchase. The listing says that for readings below 5 MΩ at any rated voltage, the test should be limited to 10 seconds, so the manual should be followed for that limit. The color code in the listing (GC-6688B-OR) is different from the model number (GCCA-6688B), so confirm the exact model on the box.

3. PEAKMETER EC-MS5205 2500V Megohmmeter (PEAKMETER)

This is a battery-powered insulation tester with a 2,500 V maximum test voltage. The listing gives a range of 0.01 to 100 GΩ and describes the unit as both digital and analog, with a digital display and an analog indicator.

Functions in the listing include automatic PI and DAR calculation, a compare function, automatic discharge for capacitive loads, a timer and a lock function for insulation tests, DC and AC voltage measurement, and continuity testing. The listing gives a weight of 1 kg, a one-year warranty, and CE, RoHS and UL marks. Because the compare function is listed, repeat tests on the same equipment can be checked against a stored reference during a maintenance cycle.

The listing does not state the exact test-voltage steps, the accuracy figure or the output current. Those values are unverified and should be checked against the manual before purchase.

How the three compare

The ETCR3500B is the only unit in this group that lists a 10 kV test voltage and the step and ramp test functions. It is the best fit for large cable or switchgear work, where the 1,000-group data store and USB export matter. Its listed host weight of 3.3 kg is also the highest of the three.

The GOLDCHAMP GCCA-6688B lists a 5,000 V top voltage and a 200 GΩ range, plus an AC voltmeter function. It is a practical choice for motor and transformer checks where 5 kV is enough, and where a single meter that also reads AC voltage is useful on the same job.

The PEAKMETER EC-MS5205 lists a 2,500 V top voltage and a 100 GΩ range. Its PI and DAR calculation, compare function and lock function suit repeat tests on the same equipment. If the job never needs more than 2,500 V, it covers the listed need with the fewest extra features.

A simple way to decide is to write down the highest voltage your equipment requires, the lowest resistance you need to read, and whether you need the ratio functions. If the answer is 2,500 V or less, the PEAKMETER and GOLDCHAMP are the closest fits. If it is 5 kV or more, the ETCR3500B or the GOLDCHAMP is the only option in this group.

Acceptance values

There is no single pass or fail value that applies to all equipment. Fluke Learn’s guidance is to compare new readings with previous readings for the same equipment at similar settings and temperature. A reading that falls sharply from one test to the next is a warning sign even if the value is still above a common reference number.

The minimum polarization index also depends on insulation class and on the standard that applies to the equipment. Fluke’s Learn material cites IEEE 43 for these minimums, but the sources we opened do not agree on a single value for every class, and the current edition should be checked before a pass or fail decision is made. Our sources do not give a value that we can apply to the three testers in this guide.

Buying notes

Pick the highest test voltage your equipment needs, not the highest the listing shows. A 10 kV tester is more than most low-voltage work requires, and the extra range can make low-voltage settings less convenient to read. Confirm the weight, the battery type and the accessory set, because the listings differ on those points. The Amazon product links are not included in this draft because none of the three models above is in our product list.

If you are new to insulation testing, read the related guides on this site before buying. The insulation resistance tester guide covers lower-voltage models for motors and wiring, and the insulation resistance test equipment guide explains the accessories that go with a megger. Use them to decide whether a high voltage unit is needed at all.

What we could not verify

The ETCR3500B listing’s claims on long-cable stability and electromagnetic interference are manufacturer statements and are not confirmed by an independent source.
The GOLDCHAMP listing’s 10-second limit for readings below 5 MΩ is stated in the listing. The manual, which we did not have, should be checked for the exact limit.
The PEAKMETER listing does not state its exact test-voltage steps, its accuracy or its output current.
No source we opened gave a single correction factor for temperature that applies to all insulation types.
The Klein Tools ET600 and Keysight insulation tester manuals were not readable in our sources, so no value from those manuals is used here.

FAQ

What is a high voltage megger used for?

It is used to measure insulation resistance on cable, motor windings, transformers and switchgear. The tester applies a DC voltage and reports the leakage resistance. A high reading usually means the insulation is holding well, but the trend across repeat tests is often more useful than a single number.

What test voltage should I choose?

Start from the equipment’s own specification. Fluke Learn’s article on insulation testers and megohmmeters gives minimum starting points for several equipment voltages, including 500 V DC for 250 V equipment and 2,500 V DC for 5,000 V equipment. Use a voltage that the equipment’s specification allows, and do not exceed the tester’s category rating.

What is polarization index?

Polarization index is the ratio of the 10-minute insulation resistance reading to the 1-minute reading. It shows whether the resistance is rising over time, which healthy insulation usually does. Many of the testers in this group calculate it automatically.

Does temperature change the reading?

Yes. Fluke Learn notes that voltage and temperature are not steady during a test and must be compensated before readings are compared. Record the temperature with each test and compare readings taken at similar temperatures.

Can I use a non-contact voltage tester instead?

No. A non-contact tester only indicates that voltage is present. It does not apply a test voltage and cannot measure insulation resistance. The non-contact voltage tester versus multimeter comparison explains what each instrument can and cannot do.

Why were the Fluke probes removed?

They are voltmeter accessories. They extend a meter’s voltage range and do not apply a test voltage, so they cannot measure insulation resistance.

Bottom line

Choose the lowest test voltage that the equipment specification allows, and then choose the tester whose range covers that voltage with a margin. If you need 5 kV or more, the ETCR3500B or the GOLDCHAMP GCCA-6688B are the options in this group. If 2,500 V is enough and you want automatic PI and DAR, the PEAKMETER EC-MS5205 is the simplest fit.

Sources

Fluke Learn, “Guide to Insulation Resistance Testing”: https://www.fluke.com/en-us/learn/blog/insulation-testers/use-insulation-resistance-testing-data-to-avert-unexpected-downtime (opened 2026-10-28)
Fluke Learn, “What is an Insulation Multimeter?”: https://www.fluke.com/en-us/learn/blog/insulation-testers/what-is-an-insulation-multimeter (opened 2026-10-28)
Fluke Learn, “Reduce Motor Downtime: Sequential Insulation Resistance Tests”: https://www.fluke.com/en-us/learn/blog/insulation-testers/reduce-motor-downtime-with-sequential-insulation-resistance-tests (opened 2026-10-28)
Fluke Learn, “Insulation Tester vs Megohmmeter”: https://www.fluke.com/en/learn/blog/insulation-testers/insulation-tester-or-megohmmeter (opened 2026-10-28)
Fluke Learn, “Improve uptime by sharing insulation resistance test data”: https://www.fluke.com/en-us/learn/blog/insulation-testers/improve-uptime-sharing-insulation-resistance-test-data (opened 2026-10-28)
Tektronix application note, “Leakage Current Test and Insulation Resistance Measurements”: https://www.tek.com/en/documents/application-note/leakage-current-and-insulation-resistance-measurements (opened 2026-10-28)