Best Insulation Resistance Tester: Top 8 of 2019

Faulty insulation is extremely hazardous to both electricians and people nearby. Using an accurate insulation resistance tester is essential to ensuring that your insulation is performing as required.

A good insulation resistance tester is easy to use, accurate, and has a wide insulation test range. A bad insulation resistance tester is a dangerous (and expensive) waste of time.

After reviewing the best insulation resistance testers on the market – we’ve found the Top 8 Insulation Resistance Testers of 2019. Buy with the confidence that you’re investing in one of the best insulation resistance testers available. Let’s jump straight into the reviews.

best overall rating
Fluke 1507 Insulation Tester
  • Huge resistance test range (up to 10 GΩ)
  • Remote test probe for hard-to-reach testing
  • Large backlit display
premium choice rating
Fluke 1587 Insulation Tester
  • 2-in-1 insulation tester + multimeter
  • CAT IV safety rating up to 600 V
  • Excellent build quality
great value rating
Extech 380260 Insulation Tester
  • Affordable price
  • Wide range of test voltages
  • Comes with test leads & hard carrying case

Best Insulation Resistance Tester

Fluke 1507 Insulation Tester – Best Overall

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Fluke 1507 Digital Megohmmeter Insulation Resistance Tester
  • Repetitive or hard-to-reach testing is easy with the remote test probe
  • Live circuit detection prevents insulation test if voltage greater than 30-Volts is detected for added user protection
  • Read measurements easily with large, backlit display

Our first choice is the Fluke 1507, and this is one of the best insulation testers around, combining a mid-range price point with a variety of features that make it capable and user-friendly. This model can test the resistance of insulation between a range of 0.01 megaohms to 10 gigaohms.

There are also a wide range of test voltages that this model can work with, from 50 V at the minimum, and climbing incrementally to 100 V, 250 V, 500 V, and finally 1000 V. As an added safety feature, the Fluke 1507 won’t let you conduct a test if the live circuit detection system sees a voltage higher than 30 V.

As an added safety improvement, the device automatically discharges capacitive voltage to reduce the likelihood of the user being shocked. The display is another advantage, as it’s larger than on competing models. This makes it easier to see your readings, and it’s also backlit to make it easier to work in the dark.

While this insulation resistance tester is capable, it’s also relatively compact and lightweight, so you won’t have any trouble fitting it into your toolbox. Weighing only 3.2 pounds, you can carry the Fluke 1507 around a worksite all day without any fatigue.

The Fluke 1507 also features a longer battery life than other models in its price range. With a brand new set of cells, it should be able to perform around 1000 insulation tests before they need to be replaced. This product comes included with the four AA batteries that are required for it to function.

With a safety rating of Cat IV, you can rest assured that this device is rated to work with higher voltages. The combination of redundant safety features and accurate readings make this one of the best insulation resistance testers for professionals.

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What We Like
  • Huge resistance test range (up to 10 GΩ)
  • Several safety features
  • Backlit display
  • True RMS reading
  • Remote test probe for hard-to-reach testing
What We Don’t Like
  • Didn’t come included with alligator clips

Fluke 1587 Insulation Tester – Premium Choice

Fluke 1587 Insulation Multimeter, LCD Display, 2 Gigaohms Insulation...
  • Manual- and auto-ranging digital insulation multimeter measures insulation resistance, current, voltage, capacitance, frequency, resistance, and temperature, and performs...
  • True RMS meter provides accurate readings when measuring linear or nonlinear loads where the current or voltage has an undistorted or distorted waveform
  • Insulation test voltages of 50, 100, 250, 500, and 1000V and insulation measurement range of 0.01 megohms to 2 gigohms

The Fluke 1587 is a lot more expensive than its smaller sibling that we just reviewed, but it’s also a lot more capable. If you like the build quality of Fluke devices and you need an insulation tester with a wide range of features, this model is designed with users like you in mind.

This product combines the features of an insulation tester with those of a multimeter, giving you a few more capabilities than the other models on this list. You can use this device manually, but the auto-ranging feature does a lot of the work for you, and the product can take a wide range of readings.

You can carefully analyze insulation resistance, temperature, frequency, current, capacitance, and more. You can even perform diode tests using this insulation tester. To ensure that you can take accurate measurements regardless of the conditions, the Fluke 1587 also comes equipped with a True RMS meter.

The range of insulation test voltages is the same as the Fluke 1507, ranging from a minimum of 50 V up to a maximum of 1000 V. The insulation measurement range on this device is between 0.01 megohms to 2 gigohms. This model features a CAT III safety rating up to 1000 V and a CAT IV rating up to 600 V.

Much like with the previous Fluke insulation tester, this model won’t let you perform a test if it detects a voltage higher than 30 V. Another similarity is that this tester features a large, backlit display, which ensures that you’ll be able to see the results of your tests without having to strain your eyes.

To ensure that the battery lasts as long as possible, this device will automatically shut down after 20 minutes of inactivity, ensuring that it won’t burn through cells. There is even a helpful low-battery indicator that will let you know when the time has come to replace them.

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What We Like
  • More versatile than other insulation resistance testers
  • CAT IV rated up to 600 V
  • Excellent build quality
  • True RMS meter
What We Don’t Like
  • Slightly pricey compared to other options

Extech 380260 Insulation Tester – Great Value

Extech 380260 Autoranging Digital Insulation Tester
  • Measures insulation resistance up to 2000M
  • 250V, 500V and 1000VDC test voltages
  • Measures AC voltage up to 750V and DC voltage up to 1000V

So far, this insulation tester from Extech is the most affordable of the bunch, which is a stark contrast to the Fluke 1587 that we just reviewed. Despite being a lot cheaper than a lot of the competition, this insulation tester from Extech is a reliable choice for the electrician on a budget.

While the Extech insulation tester gives up a few bells and whistles for a more affordable price point, it retains what counts: excellent build quality, accurate readings, and extra safety features. The insulation resistance testing range for this model is between 200 megohms and 2000 megohms.

The voltage range for testing ranges from 250 V, 500 V, up to 1000 V. Like with the last two insulation resistance testers, this model also features a backlit display with large readings so that you can see them from further away. The screen shows both the test voltage and insulation resistance.

The ability to lock this device on continuous mode means that you don’t have to keep hold of it so that it can do its job. This is handy when you’re working alone, and you need to divert your attention to something else. To keep the user safe, the device will automatically discharge at the end of every test.

With a basic accuracy level of +/- 3%, this is one of the most accurate models in its price range, and we didn’t notice any glaring errors while we were using it. Surprisingly for an affordable model, it also comes included with everything that you need to get started, including 6 AA batteries, test leads, alligator clips, and a carry case.

To ensure that this device can withstand the rigors of the worksite, it has a double molded housing which can protect the internal components from impacts. Weighing only 24.6 ounces, this is also one of the lightest insulation resistance testers available.

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What We Like
  • Affordable price
  • Reliable
  • Comes with test leads & hard carrying case
  • Accurate readings
What We Don’t Like
  • Fewer features than other top models

Megger MIT230 Insulation Tester

Megger MIT230-EN Insulation Tester, 1000 Megaohms Resistance, 250V,...
  • Insulation tester for testing insulation resistance, voltage, and continuity in electrical installations
  • Average-sensing meter provides accurate readings when measuring linear loads, where the current or voltage has a sinusoidal waveform
  • Dual digital display with analog arc function to replicate response of analog meters

Moving back to mid-range products, the MIT230 from Megger is a relatively capable device with a few features that set it apart from the pack. The inclusion of an average sensor means that you can measure linear loads without having to calculate the average readings yourself.

Moving back to mid-range products, the MIT230 from Megger is a relatively capable device with a few features that set it apart from the pack. The inclusion of an average sensor means that you can measure linear loads without having to calculate the average readings yourself.

While this device features a digital display, it is also equipped with an analog-style meter so that users of both types of insulation testers can be comfortable with it. This model can measure insulation resistance from 0 to 1000 megohms, and it can read voltages ranging from 25 V to 600 V.

Ensuring that the user is safe, the MIT230 is CAT III rated up to 600 V. The device itself is also IP40 rated so that obstacles in the work area can’t damage it. This tester features a simple set of controls which are all outlined, making it an excellent choice for beginners.

The compact design of this insulation tester also makes it more portable than other models in its price range. However, a few key issues hold it back from being one of our top three. The most significant problem is that the screen on this tester is much smaller than on the other three that we’ve reviewed so far.

Another problem is that this model doesn’t offer any distinct advantages over the Fluke 1507, despite being quite a bit more expensive than it. Despite these issues, this is still an excellent insulation tester; it just doesn’t offer the same value for money as the best ones available.

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What We Like
  • Average sensor for linear loads
  • CAT III rated to 600 V
  • IP40 ingress protection
What We Don’t Like
  • Small display
  • Similar competitors available for cheaper

Amprobe Insulation Resistance Tester

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Amprobe AMB-25 Digital Insulation Resistance Tester
  • Insulation resistance meter to test insulation of wires, cables, transformers, and electrical motors
  • Digital meter with automatic range selection
  • Internal memory stores up to 9 test results

Going back to affordable products, this insulation resistance tester is just a little more expensive than our top budget choice from Extech. This is one of the better budget insulation resistance testers available, as it comes equipped with some helpful features like internal memory and automatic range selection.

The memory feature allows you to save up to nine sets of results so that you can reference them later. This can come in handy when you don’t have anywhere to mark down the results, or if you don’t want to have to fumble around with your phone or with a note pad to remember them.

The Amprobe tester can measure resistance between 0 and 1000 megohms, and it features DC test voltages of 250 V, 500 V, and 1000 V. This is also one of the safest budget resistance testers available, as it features a CAT III rating up to 1000 V.

This insulation resistance tester features a rugged housing that is designed to put up with plenty of abuse on the job. Unlike many of its competitors, the Amprobe resistance tester is also extremely reliable, as these devices are known to keep working correctly for years.

Unfortunately, this resistance tester is more expensive than the Extech model, and it doesn’t come included with as many extras. While this would make sense if there were a significant performance gap between the two models, you’re essentially getting less for more when you compare this to the Extech tester.

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What We Like
  • Durable and reliable
  • Cat III rated to 1000 V
  • Memory feature
What We Don’t Like
  • Doesn’t come with enough extras
  • Pricier than other budget testers

AEMC Insulation Resistance Tester

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AEMC 2126.53 Digital Megohmmeter, 1000V
  • True Megohmmeter
  • Insulation test voltage selections of 250V, 500V and 1000V
  • EST LOCK feature for timed measurements up to 15 minutes

Moving on to yet another budget resistance tester, this model from AEMC is an excellent option for customers that are looking to save money. You have a choice of three insulation test voltages when using this device: 250 V, 500 V, and 1000 V. As for resistance, the device can measure between 1 kΩ and 4000 MΩ.

The continuity test feature has a beeper so that you can hear the results if your resistance is under 35 Ω. The device also features overload protection rated at 600 Vrms. If you’re trying to perform extended tests, you can lock the test button for up to 15 minutes, ensuring that you won’t have to tire your hands.

This model is also one of the lightest insulation resistance testers in its price range, only weighing 24 ounces. If you need something portable that you can easily bring with you to your job, then you shouldn’t have any trouble carrying around this insulation tester for longer periods.

The backlit digital display allows you to work with this insulation resistance tester in the dark, and it has a rating of IP51 so that it can resist dust and drops of water. This resistance tester also has a longer battery life than its competitors, though it uses six AA batteries, as opposed to the four used by some other testers.

Unfortunately, this resistance tester isn’t as reliable as some of the other models on this list, and you may have to sometimes restart it before it starts working again.

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What We Like
  • Reasonable price
  • IP51 rating
  • Lightweight
What We Don’t Like
  • Unreliable
  • Flimsy housing

Reed Insulation Resistance Tester

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REED Instruments R5600 Insulation Tester and Multimeter (Megohmmeter),...
  • Test voltage combinations: 250V, 500V or 1000V
  • 1mA test current for megaohm range at rated voltage
  • 200mA test current for continuity range

The Reed insulation resistance tester has a few more features that you would expect from a model of its price. A few of them help make it easier to use. Combined with the low price, they make this product an attractive choice for beginners who have never purchased an insulation resistance tester before.

The large display clearly outlines the insulation resistance and the test voltage, and it’s also backlit so that you can easily see it in the dark. With test voltages of 250 V, 500 V, or 1000 V, this model is also versatile, and you can tests insulation resistance up to 2000 megohms.

The lock feature allows the resistance tester to operate continuously without your finger being held down, making it easier to conduct long-term tests. There is also a hold key so that you can retain the data on the screen for later reference, though keep in mind that the device shuts off automatically to conserve its battery.

Unlike other budget resistance testers, this one is built to last, and it features a double molded housing that protects it from impacts and other physical damage. This is also one of the safest products at its price point, as it has a CAT III safety rating at up to 1000 V.

Unfortunately, this product suffers from poor battery life, even with its auto-shutdown feature. It is much less efficient than some of the other products that we’ve already gone over. However, if you’re looking for a budget resistance tester, the Reed  R5600 is still a decent choice.

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What We Like
  • Low cost
  • Durable construction
  • Comes with a carry case and a strap
What We Don’t Like
  • Short battery life
  • Buttons are stiff

Supco M500 Megohmmeter

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Supco M500 Insulation Tester/Electronic Megohmmeter with Soft Carrying...
  • Measure insulation values up to 1000 me ohms at 500 VAC
  • Zone scale to indicate insulation condition
  • Hand held

The M500 from Supco is one of the most uncomplicated products on this list, as it doesn’t feature a digital display like the rest of the competition. It can measure the resistance of insulation ranging from 0 to 1000 megohms, and the simple interface lets you know the result through a series of lights.

Despite being far simpler than the other kinds of insulation resistance testers, this model is also more reliable as there are fewer components that can fail. Since this device is far simpler than many of the other ones that we’ve looked at, it’s also a lot more affordable, being the cheapest option on this list by far.

For such a low price, you would expect to face issues with durability and long-term reliability, but we were impressed by how robust this model is. The Supco megohmmeter is built to higher standards than most budget models, and we didn’t run into any issues when we were testing it out.

Since it’s far simpler than other insulation resistance testers, this megohmmeter is also lighter than the competition, weighing only 12 ounces. The M500 also comes included with a soft carry case so that it can be stored safely when it is not in use.

Despite these advantages, this model is just too simple to compete with the top three choices on this list. Since this device can only read resistance, it is a lot less versatile than competing models which are also capable of taking voltage readings. Taking a reading at a glance is also complicated by the way the results are displayed.

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What We Like
  • Very cheap
  • Extremely light
What We Don’t Like
  • No screen
  • Only measures megohms
  • Lacks versatility


About Blake Sutton

Blake has worked as an electrician for over 10 years, receiving his Journeyman Electrician license in 1998. Looking to take his professional electrical career further, in 2008 he received his Bachelor of Science in Electrical Engineering (BSEE) from the University of Texas in Austin. Blake now works full time as an electrical engineer, specializing in power systems.