Best Insulation Resistance Tester

Electrical insulation is crucial in any power system, even at low voltages. It is what prevents short circuits and possible electrocution that can be fatal. Therefore, it is undeniably crucial to test their effectiveness with reliable devices designed for that before installation. Every insulator used should effectively resist electric current flow.

Testing the insulation resistance is accomplished using a tester or megohmmeter. Some people call it a megger tester or earth tester. But regardless of the name, it is designed to prevent possible electrical shock or short circuits caused by insulation breakdown. Megohmmeters are used to test insulation resistance during and after installation. That is because insulations degrade over time and may lose their effectiveness in resisting current flow.

Most insulation testers in the market double up as multimeters. That means they can also measure current and voltages in energized power systems. But in this review, we will focus on the best insulation testers or megohmmeters in the market without considering their secondary functions. Let’s dive in for more details!

Insulation Resistance Tester

Best Insulation Resistance Tester Reviews

Buying the best megohmmeter can be challenging because of the myriad options in the market. These products have varying features regarding the range of resistance measurements they can take. But many of them are in mega ohm ranges, much higher than what the usual digital multimeter or ohmmeter can measure.

Let’s quickly review the best insulation resistance testers, outlining their capabilities and features that set them apart.

1. Fluke 1507 Digital Megohmmeter

The Fluke 1507 Digital Megohmmeter appears at the top of this list of the best megohmmeters for various reasons. It is compact, versatile, portable, feature-rich, and relatively affordable compared to some high-end megger testers. This device is ideal for insulation resistance measurements, troubleshooting, commissioning, preventive, and maintenance power system applications.

This device can perform insulation tests from 0.01 MΩ to 10 GΩ with the highest accuracy possible. It also measures AC and DC voltages up to 600V. Thanks to its safety features and CAT IV safety ratings. Fluke 1507 Digital Megohmmeter is the ultimate tool for every professional. Refer to the manufacturer’s website for more features and specifications that make it the best megohmmeter.

Insulation Specifications
Measurement range 0.01 MΩ to 10 GΩ
Test voltage 50 V, 100 V, 250 V, 500 V, 1000 V
Test voltage accuracy + 20%, – 0%
Short circuit current 1 mA nominal
Auto discharge Discharge time < 0.5 second for C = 1 µF or less
Live circuit indicator Inhibit test if terminal voltage > 30 V prior to initialization of test
Maximum capacitive load Operable with up to 1 µF load
Measure accuracy 50 V ± (3% + 5)
100 V ± (3% + 5)
250 V ± (1.5% + 5)
500 V ± (1.5% + 5)
1000 V ± (1.5% + 5) to 2000 MΩ, ± (10% + 3) above 2000 MΩ
Earth Bond Resistance Measurement
Range/Resolution 20.00 Ω 0.01 Ω
200.0 Ω 0.1 Ω
2000 Ω 1.0 Ω
20.00 kΩ 0.01 kΩ
Accuracy ± (1.5% + 3)
Overload protection 2 V rms or DC
Open circuit test voltage > 4.0 V, < 8 V
Short circuit current > 200.0 mA

 

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Pros:

  • High resistance test range of up to 10 GΩ
  • Large backlit LCD display
  • True RMS reading
  • Highly accurate
  • Many safety features and certifications, including CAT IV 600V rating
  • Remote test probe for use in hard-to-reach places
  • Long battery life – performs more than 1,000 insulation tests before requiring battery replacement.

Cons:

  • No alligator clips

2. AEMC 2126.53 Digital Megohmmeter

AEMC 2126.53 is a multi-range true megohmmeter that measures insulation resistance from 1kΩ to 4000MΩ. It is one of the best in the market regarding resistance range but nowhere near the first product, which is the best insulation resistance tester on this list.

This device also doubles up as a multimeter for measuring DC voltages up to 1,000V and AC voltages up to 600V. It also features a continuity test function with an audible beep for short circuits or resistances below 35 ohms.

The AEMC 2126.53 is the best choice for testing insulations on switch gears, motors, DC generators, cables, power tools, and small appliances. Like the first choice, it is best for professionals and electricians working with high-voltage power systems.

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Pros:

  • Relatively affordable
  • Lightweight design
  • True megohmmeter
  • CAT IV 600V safety compliance
  • Backlit digital display with bar graph
  • EST LOCK feature for timed measurements up to 15 minutes
  • Auto discharge after insulation test

Cons:

  • Relatively low ohm rating
  • Flimsy housing

3. Klein Tools ET600 Multimeter Megohmmeter

Klein Tools ET600 Multimeter Megohmmeter is the best choice if you are looking for a cost-effective device for insulation resistance testing. It is one of the best megohmmeters on this list for its many features. It would have scored higher if not for its low resistance range. Despite being an accurate device, you can only use it for testing electrical insulation resistances up to 4,000 MΩ.

The Klein Tools ET600 is an auto-ranging true RMS ohm meter that doubles as a multimeter. It can measure AC and DC voltages up to 1,000V in different power systems. This is backed up with many safety features that make it CAT IV 600V and CAT III 1,000V safety compliance. And what’s more? You can choose your preferred voltage range for the application. It is best for insulation resistance testing and electrical system installation and maintenance.

Other features of this device include a backlit LCD display unit, auto-power off, hold function, low battery indicator, etc.

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Pros:

  • Offers multiple measurement options
  • Relatively affordable
  • Lock button for insulation resistance testing
  • Warning alarm and high voltage icon for detection of voltage
  • Auto-power off
  • Automatic ranging true RMS technology for enhanced accuracy
  • Built-in stand and optional magnetic hanger for hands-free operation

Cons:

  • Not ideal for small applications and require experience
  • Short resistance range

4. AEMC 6505 Megohmmeter

If you are ready to break the bank for an insulation resistance tester, AEMC 6505 Megohmmeter is the best choice. It is a true RMS portable device housed in a rugged carrying case for field use. This device can be powered by removable batteries or hooked directly to the power line.

With AEMC 6505 Megohmmeter, you can professionally perform voltage, insulation, and capacitance measurements. It features a large LCD screen that clearly displays the measured values and calculated results, such as Dielectric Absorption Ratio (DAR) and Polarization Index (PI).

For resistance measurements, this device has a measurement range of up to 10 TΩ. It could have been the best megger tester if not for its insanely high price.

AEMC 6505 Megohmmeter also has safety features, including recessed test terminals to ensure your safety. It complies with CAT III 1,000V and other international safety certifications.

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Pros:

  • High resistance measurement range of up to 10 TΩ
  • Many safety features and CAT III 1,000V compliant
  • Accurate and reliable
  • Rugged field case for protection and safety portability
  • Adjustable and programmable test voltage
  • Automatic DAR and IR calculations

Cons:

  • Very expensive
  • Relatively heavy and bulky with the carrying field case

5. UEi IRT807 Advanced Insulation Resistance Tester

UEi IRT807 ohm meter is another portable option if you want an insulation resistance tester. The device offers voltage testing at 50V, 100V, 250V, 500V, and 1000V with a range of 0.01MΩ-2GΩ. Refer to the specification chart below for more ratings and the ability of this megohmmeter. It, however, does not show full capability because other functions are left out.

UEi IRT807 ohmmeter can also measure AC and DC voltages and continuity while ensuring safety. It complies with the high safety ratings of CAT IV 600V and CAT III 1,000V.

This device can also compute polarization index (PI) and dielectric absorption ratio (DAR) and show results on a large backlit LCD screen. You can also use its many reading functions, including zero, hold, lock, and compare. Its other features include a protective rubber boot with a kickstand, test lead holders, and auto power off to conserve battery when not in use.

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Insulation Specifications
Measurement range 0.01MΩ to 2GΩ
Test voltage 50 V, 100 V, 250 V, 500 V, 1000 V
Test voltage accuracy 0 to +20%
Short circuit current 1 mA nominal
Auto discharge Discharge time < 0.5 second for C = 1 µF or less
Live circuit indicator Inhibit test if terminal voltage > 30 V prior to initialization of test
Maximum capacitive load Operable with up to 1 µF load
Measure accuracy 50 V ± (3% + 5)
100 V ± (3% + 5)
250 V ± (1.5% + 5)
500 V ± (1.5% + 5)
1000 V ± (1.5% + 5) to 600 MΩ, ± (10% + 3) above 600 MΩ
Earth Bond Resistance Measurement
Range/Resolution 20.00 Ω 0.01 Ω
200.0 Ω 0.1 Ω
2000 Ω 1.0 Ω
20.00 kΩ 0.01 kΩ
Accuracy ± (1.5% + 3)
Overload protection 2 V rms or DC
Open circuit test voltage > 4.0 V, < 8 V
Short circuit current > 200.0 mA

Pros:

  • Automatic DAR and IR calculations
  • Hold functions
  • Protective rubber boot
  • Kickstand for hand-free operation
  • Test lead holders
  • Safe to use – CAT IV 600V and CAT III 1,000V complaint

Cons:

  • The resistance range should have been better

6. Fluke 1577 Insulation Multimeter

Fluke 1577 is a 2-in-1 device that combines a digital insulation resistance tester with a full-featured true RMS digital multimeter. Apart from being used as a megohmmeter, Fluke 1577 can also measure AC and DC voltages, current, temperature, and resistance. For insulation resistance testing, this device measures up to 600 MΩ. It is not the best, but its accuracy and reliability allow it to feature on this list. Check out detailed specifications on the manufacturer’s official website.

The fluke 1577 is designed and built to work in a challenging environment. It is waterproof and dustproof and ruggedly designed to withstand a 10-foot drop. This device also has safety features that protect you from voltage spikes and ensure your safety.

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Pros:

  • Optional rubber hanger for hand-free operation
  • Waterproof and dustproof – IP67-rated
  • Safe to use – comply with CAT III 1,000V and CAT IV 600V safety standards
  • Multipurpose – measures resistance, voltage, current, capacitance, and frequency
  • Can withstand a 10-feet drop
  • Backlit LCD to enhance readability under low light conditions
  • Long battery life

Cons:

  • Relatively expensive
  • Low resistance range for a device within its price range

7. Extech 380260 Autoranging Digital Megohmmeter

Extech 380260 is an auto-ranging digital megohmmeter designed to measure insulation resistance and also allows you to measure voltages ranging between 250V, 500kV, and 1,000V DC. However, it has a relatively small resistance range of only up to 2,000 MΩ.

Other features of this device include automatic discharge after an insulation resistance test, Lo Ohm function for testing connections, data hold, and lock power function for hands-free operation. You also use it for continuity testing and resistance measurements.

As a bonus, Extech 380260 has a large, easy-to-read dual display for showing readings and test results. The backlit LCD screen makes it suitable for use under low-light conditions.

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Pros:

  • Highly compact for portability
  • Dual backlit LCD display
  • Offers insulation test for voltages up to 1,000V
  • Provides very accurate readings
  • Durable and reliable
  • Lock power on function for hands-free operation
  • Data Hold to freeze displayed reading

Cons:

  • Low resistance range for its price
  • Fewer features compared with competing models

8. REED Instruments R5600 Insulation Tester

REED Instruments R5600 is also one of the best megohmmeter testers for a tight budget. You can consider this device if you don’t have thousands of dollars to spend on an insulation resistance tester.

This device can perform 250V, 500V, and 1,000V tests and has insulation resistance up to 200 MΩ. Other features and functions include a hanging strap for hands-free operation, a lock function, a Lo Ohm function, and a low battery indicator.

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Pros:

  • Large backlit dual LCD display
  • Lo Ω function for testing connections
  • Data hold function
  • Relatively affordable
  • Cat. III, 1000V safety rating

Cons:

  • Low resistance range

9. Supco M500 Insulation Tester

Supco M500 is a handheld, compact megohmmeter designed for affordability. Despite its low price, it remains one of the most accurate insulation resistance testers. This device has a resistance range of 20 to 1000 MΩ at 500 VAC and colored LED lights that instantly verify the condition of the electrical insulation.

The LED display is color-coded to help you interpret different conditions. It is divided into three zones: bad, caution, and red. Red LED indicates damaged insulation resistance of up to 20 MΩ or a short circuit.

On the other hand, yellow lights illuminate for resistances between 40 and 100 MΩ for the caution zone and green lights for resistances between 150 to 1,000 MΩ to show a good zone. All the zoning LEDs go off if the insulation resistance exceeds 1,000 MΩ.

Supco M500 Insulation Tester is ideal for testing motor winding insulation and diagnosing heat damage on different appliances.

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Pros:

  • Affordable
  • Easy to use
  • Clear LED indicators
  • Accurate

Cons:

  • Short resistance range
  • Limited features and functions

10. UNI-T UT501A Insulation Resistance Tester

UNI-T UT501A Insulation Resistance Tester is the last device on this list of the best ohm meters and the most affordable. It can be used for insulation resistance measurements of different electrical equipment and insulation materials, including cables, switches, motors, transformers, etc.

Despite the affordability, this device has impressive specs; refer to the specification chart for detailed information. It also boasts high precision and accuracy, the same as a high-end megohmmeter.

Other functions of UNI-T UT501A include auto range, high voltage indication, low battery indication, auto discharge, and overload indication.

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Insulation Resistance Range Accuracy
Test Voltages 100V, 250V, 500V, 1000V 0 – 10%
 100V Insulation Resistance Ranges 0 to 100MΩ ± (3% + 5)
 250V Insulation Resistance Ranges 0 – 99.9MΩ
100MΩ – 5.5GΩ
± (3% + 5)
± (3% + 5)
 500V Insulation Resistance Ranges  0 – 99.9MΩ
100MΩ – 5.5GΩ
± (3% + 5)
± (3% + 5)
 1000V Insulation Resistance Ranges  0 – 99.9MΩ
100MΩ – 5.5GΩ
± (3% + 5)
± (3% + 5)
 Load/Current 250V (R=250KΩ) 1mA
500V (R=500KΩ) 1mA
1000V (R=1000KΩ) 1mA
2500V (R=2500KΩ) 1mA
0 to 10%
0 to 10%
0 to 10%
0 to 10%
Short Circuit Current <2mA
 AC Voltage ± (2% + 3)
Display type 1,999 count backlit LCD

 

Pros:

  • Very affordable
  • Relatively high resistance range
  • Many features and functions for the price
  • Low power warning and auto-off functions
  • Precise and accurate

Cons:

  • Relatively low build quality

Best Insulation Resistance Tester Buying Guide

Consider the following factors for the best insulation tester:

1. Insulation Resistance Test Range

This parameter defines the capability of the megohmmeter. It will depend on the intended purpose, but a device with a high resistance range in the GΩ or TΩ is the best choice if you switch to higher power systems. Notably, products within this range are expensive.

2. Voltage and Safety Rating

These two parameters define where the device will be used. You cannot use a tool rated for 500V on 600V or 1,00oV power systems. You don’t want to end up with a fried device or get electrocuted. So, choose the appropriate voltage and safety rating to match the intended application.

3. Portability

The overall design of an insulation resistance tester determines its portability. Go for a more compact device since it is easier to carry around.

4. Price and Manufacturer’s Warranty

The best megohmmeters are often pricey, especially if they check all boxes. This may force you to wait until you have enough in your budget for a high-end device that will serve for many years. Additionally, consider the stated manufacturer’s warranty. The higher the period, the more reliable the product is.

FAQs

Q: How is insulation resistance measured?

A: Insulation resistance is measured using Ohm’s law. Testers apply known voltage to the insulation material under test and measure the current around its surface due to the applied voltage. The resistance can then be calculated by applying the formula R=V/I.

Q: Can I use a multimeter instead of an insulation resistance tester?

A: Yes. You can use a multimeter to measure the insulation resistance if it has the resistance range for the application. After all, an insulation resistance tester is a type of ohm meter, which a multimeter can be when the appropriate setting is selected.

Q: Can you megger with a multimeter?

A: No. You can’t megger with a multimeter because it cannot produce high voltages across its terminals needed for the test. Megger meters, on the other hand, generate up to 1,000V DC.

Q: What makes insulation testers different from megohmmeters?

A: Megohmmeters are designed to only measure insulation resistance. On the other hand, most insulation testers double as multimeters. They can also measure voltages, currents, capacitance, and even temperature and conduct continuity and diode tests.

Conclusion

The Fluke 1507 Digital Megohmmeter carries the day as the best insulation resistance tester. It is recommended for professionals for its remarkable features and functions at a price that does not break your bank account. It is also very accurate and safe to use on high-voltage power systems.

The second option is the AEMC 2126.53 insulation tester. Like the first choice, it is also relatively affordable. But it has all features you would expect in a high-end device, including high safety ratings and reliability.

Klein Tools ET600 Multimeter Megohmmeter is not the most affordable device on the list but a cost-effective option. It is one of the most popular insulation testers with proven reliability. And it also has as many features as high-end devices.

You can also use the provided buying guide to decide on the best insulation tester to suit the application.

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