Meet Your Match – Choosing the Perfect Insulation Resistance Tester

13 February 2020


If you weren’t thrilled by our spooky blog or you weren’t feeling festive when we threw some holiday cheer at you, then you’re probably going to dislike this week’s blog too. Sorry in advance. But wait, before you leave – just hear us out. In case you didn’t know, Valentine’s Day is on Friday. If you were truly unaware – props to you; they’ve been selling pink and red candy at the store for over a month now, so we are impressed by your disregard for the impending holiday.

Regardless of your relationship status, we aren’t here to sell you chocolates and we definitely can’t help you find a significant other by Friday.

What we can do though is help you find a different kind of love – the perfect insulation resistance tester.

Yes, we said it. It can be difficult to find the perfect one, we know; with endless options, features, applications, and add-ons, the task seems significantly more daunting than it needs to be. We are going to give you some earth-shattering truth though on this Valentine’s Day Eve.

All of our insulation testers perform essentially the same test.

Yep, you read that right. Plus, they do that test in the same reliable and accurate manner, regardless of the model. When it comes to refinements and additional features, that’s where you have a decision to make. Don’t worry though, we are here to help - that’s literally the purpose of this blog. It’s these additional features that separate one model from the next and can help you find a unit that fits your particular application needs – to a t. 

Fortunately, you don’t have to follow your heart when it comes to selecting a tester, you just need to follow these nine simple steps. After you’ve gone through our checklist, your number of potential partners should have dwindled significantly. At this point, it’s up to personal preference, so we’ll give you the go ahead to follow your heart.


So, how do I choose an insulation tester?

1. Test Voltage

The first thing you’re going to need to look at when choosing an insulation tester is your job title. If you don’t know this, do not move on to step 2; do not pass go; do not collect $200. We recommend going to talk to your HR department first, nail down your job title, and then proceed to step 1, again.

Once that’s settled, you’re ready to look at test voltage. If you’re an electrician – only interested in installation testing – you probably only need a single voltage. Whereas, if you’re more of a repair and maintenance technician, you’re likely going to want an instrument with diagnostic capabilities that can compare various tests at different voltages. Right?

You should also base your voltage requirements on the rated voltage of the equipment you are working with, specifically whether or not you will be performing tests at or above rated, i.e. stress tests.

Something to keep in mind is that pervasive insulation damage, such as moisture ingress, is revealed at any voltage; whereas mechanical damage usually requires a higher voltage for detection – capable of arcing an air gap.

With 1 kV, 2.5 kV, and 5 kV models to choose from, this may be the most critical decision you have to make. But keeping our above advice in mind, you’re well on your way to finding your forever.

2. Measurement Range

Unfortunately, you’re not done yet, not even close. If you’re an electrician or repairman – primarily interested in proofing – you can get away with an instrument that provides infinity readings, since you are just concerned with meeting or exceeding a certain resistance, rather than knowing the specific measurement. It’s more of a pass or fail ordeal.

However, if you are working in the realm of predictive maintenance, it’s critical to know exactly how your measurements change over time, specifically in the upper values of resistance. Thanks to recent technology upgrades, certain instruments allow you to test into the tera ohm range (TΩ) – giving you the capability to differentiate between elevated resistance measurements over time. It may be helpful to determine the exact insulation resistance values of your equipment when it’s new, and then choose a tester that can truly measure those values.

3. Power Source

The test is the same, regardless of the power source you’re using. At the end of the day, it comes down to this: alkaline batteries (like AA), hand-cranks, and rechargeable batteries can all deliver the same level of voltage you’re looking for – even 1,000 volts, believe it or not. Like anything, there are advantages and disadvantages to each.

For example, batteries free the operator from physically “cranking”, while hand-cranks take away the dependence on batteries or the possibility of human error. At the same time, hand-cranks can be a literal pain, if you have to run a test for 10 minutes or more (like a Polarization Index test). Unless you were looking for a workout, you ideally don’t want to be cranking for 10 minutes. Rechargeable batteries are likely the most convenient, unless you forget to recharge – then, throwaways are for you!

4. Voltage Detection

Each of our models will detect unwanted voltage on the item under test, which is great. It’s up to you though, whether you want an audible warning signal or a visual display on the monitor.

5. Display

That bring us nicely to the next feature under consideration – display. Digital or analog? Again, it’s largely a question of personal preference. If you’re truly indecisive, some newer models combine both capabilities in a single unit, so look out for those.

6. Ω/kΩ Ranges

Okay, these are commonly referred to as “continuity” and “resistance” ranges, which greatly enhance the depth of your testing capabilities. If you’re looking at two (or more) testers with similar functions, the Ω/kΩ ranges can help you differentiate between the two and solidify your decision. Ohm ranges can help you verify the integrity of circuits and connections, while kilohm ranges are helpful for identifying areas of insulation deterioration.

Electricians, you’re going to want the ohm range; maintenance men and women, check out the kilohm range; and repair people, you’re probably going to want both features!

7. Guard Terminal

If you want to eliminate certain components of leakage from your measurements, you should take the guard terminal into consideration. While electricians likely don’t need this third terminal, maintenance personnel should, and repairmen definitely will.

8. Price

Home stretch, ladies and gentlemen! This is a quick one. From a few hundred to several thousand dollars, we have an insulation tester for every budget. Don’t let the price tag fool you either. Regardless of your budget, you’ll find a model that not only fits your testing requirements, but also offers a range of additional features too.

9. “Extra” Features

Speaking of features, there’s a few extra ones to be aware of.

Please keep the following statement in mind when you are selecting a tester. From one model to the next, the accuracy and reliability of measurements never changes; it’s the additional capabilities and testing flexibility that changes between units.

Newer models offer pre-programmed standardized tests, such as Polarization Index, Step Voltage, and Dielectric Discharge, along with calculation and storage of results, downloading capabilities, timed tests, leakage current measurements, and a “burn mode”.

Depending on your situation, these may or may not be necessary, but they certainly are convenient to have. We recommend that if it fits your budget – go for it!

There you have it. The nine things to consider when looking for your perfect match.    


-Meredith Kenton / Digital Marketing Assistant / Valley Forge, Pennsylvania