An insulation resistance tester (also known as a Megohmmeter or “megger”) is a type of ohmmeter used to evaluate the electrical resistance of insulators.
Faulty insulation is extremely hazardous to both electricians and people nearby – a bad insulation resistance tester is a dangerous (and expensive) waste of time.
On the other hand, a good insulation resistance tester is easy to use, accurate, and has a wide insulation test range.
After meticulously reviewing the best insulation resistance testers & megohmmeters on the market – we’ve found the Top 8 Insulation Resistance Testers of 2021.
Buy with the confidence that you’re investing in one of the best insulation resistance testers available. Let’s jump straight into the reviews.
- Huge resistance test range (up to 10 GΩ)
- Remote test probe for hard-to-reach testing
- Large backlit display
- 2-in-1 insulation tester + multimeter
- CAT IV safety rating up to 600 V
- Excellent build quality
- Top 8 Best Megohmmeter Insulation Resistance Testers
- Fluke 1507 Megohmmeter Insulation Tester – Best Overall
- Fluke 1587 Insulation Tester (2 Gigaohms) – Premium Choice
- Extech 380260 Insulation Tester – Great Value
- Megger MIT230 Insulation Tester (1000 Megaohms)
- Amprobe Insulation Resistance Tester (1000 Megohms)
- AEMC Megohmmeter Insulation Resistance Tester
- Reed Instruments Megohmmeter Insulation Resistance Tester (2000 Megohms)
- Supco M500 Megohmmeter Insulation Tester (1000 Megohms)
Top 8 Best Megohmmeter Insulation Resistance Testers
Fluke 1507 Megohmmeter Insulation Tester – Best Overall
- 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 a 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. If you need any more info, you can read our full in-depth Fluke 1507 review.Check Price
- Huge resistance test range (up to 10 GΩ)
- Several safety features
- Backlit display
- True RMS reading
- Remote test probe for hard-to-reach testing
- Didn’t come included with alligator clips
Fluke 1587 Insulation Tester (2 Gigaohms) – Premium Choice
- 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
Although the Fluke 1587 more expensive than its smaller sibling the Fluke 1507 (which we reviewed above), the Fluke 1587 comes jam-packed with extra features to justify the price. 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.
Its standout feature is its auto-ranging – allowing you to measure insulation resistance, current, voltage, capacitance, frequency, resistance, and temperature, and performs diode tests for testing line insulation on motors, generators, cables, and switchgear.
One of the biggest benefits when comparing the Fluke 1507 vs 1587 is that not only is the Fluke 1587 a digital insulation tester, but it is also a genuine True RMS digital multimeter. This is a huge plus, as with the Fluke 1587 you can now take accurate readings when measuring linear or nonlinear loads where the current or voltage has an undistorted or distorted waveform.
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.
Overall the Fluke 1587 is the highest-quality and most versatile insulation tester on the market. It also functions as a True RMS multimeter, which makes it ideal for those who want an all-in-one tool to carry with them while performing their electrical work.
It costs a bit extra – but it is well worth the price for the professional electrician who will be frequently taking insulation and resistance readings. If you need any more info, you can read our full in-depth Fluke 1587 review. Highly recommended.Check Price
- Low-pass filter blocks unwanted voltages when measuring AC voltage and AC frequency
- CAT IV rated up to 600 V
- Excellent build quality
- True RMS meter provides accurate readings when measuring linear or nonlinear loads
- Certified IP40
- Slightly pricey compared to other options
Extech 380260 Insulation Tester – Great Value
- 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 (unlike Extech’s clamp meter). 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, multimeter 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.Check Price
- Affordable price
- Comes with test leads & hard carrying case
- Accurate readings
- Fewer features than other top models
Megger MIT230 Insulation Tester (1000 Megaohms)
- 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 is an excellent megger insulation tester 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 that 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 the best megger tester available on the market. So if you’re specifically looking for a megger insulation tester, then this is the best option for you.Check Price
- Best Megger Insulation Tester on the market
- Average-sensing meter provides accurate readings when measuring linear loads
- CAT III rated to 600 V
- IP40 ingress protection
- Small display
- Similar competitors available for cheaper
Amprobe Insulation Resistance Tester (1000 Megohms)
- 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 380260 Insulation Tester.Check Price
- Durable and reliable
- Cat III rated to 1000 V
- Memory feature
- Doesn’t come with enough extras
- Pricier than other budget testers
AEMC Megohmmeter Insulation Resistance Tester
- 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 megohmmeter, 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. Overall the AEMC Megohmmeter Insulation Resistance Tester is good but falls short of the Fluke 1507 megohmmeter in terms of features, and is more expensive than the Extech 380260. Only go with this megohmmeter if you’re a diehard AEMC fan.Check Price
- Reasonable price
- IP51 rating
- True Megohmmeter
- Unreliable (made in China)
- Flimsy housing
- Although a true Megaohmmeter, has a low-ohm rating
Reed Instruments Megohmmeter Insulation Resistance Tester (2000 Megohms)
- Test voltage combinations: 250V, 500V or 1000V
- 1mA test current for megaohm range at rated voltage
- 200mA test current for continuity range
The Reed megohmmeter insulation 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 megohmmeter, the Reed R5600 is still a decent choice.Check Price
- Low cost
- Durable construction
- Comes with a carry case and a strap
- Short battery life
- Buttons are stiff
Supco M500 Megohmmeter Insulation Tester (1000 Megohms)
- Measure insulation values up to 1000 me ohms at 500 VAC
- Zone scale to indicate insulation condition
- Hand held
The Supco M500 Megohmmeter 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.Check Price
- Very cheap
- Extremely light
- No LCD screen makes it difficult to use
- Only measures megohms
- Lacks versatility