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Electrical Tester Contractor edition
March 2016
The next step in insulation testers - Don't over do it

The next step in insulation testers - Don't over do it

02 March 2016

MIT430 in use on circuit boardPortable insulation testers have been around a long time – since 1889 in fact, when the forerunner of the original Megger first became available. The testers used by today’s contractors, however, bear very little resemblance to the earliest instruments, even though they do a similar job. In fact, portable insulation testers have evolved and developed over the years, and that process of development is still going on, with Megger continuing to lead the way.

But what could possibly be done to improve the very capable models that we see today? Actually, even though the current crop of testers are undoubtedly capable of doing a good job, there is still plenty of scope for further improvement.

Consider, for example, the test voltage. You’ve set your instrument to 500 V, but how do you know it is actually delivering that voltage? The IET Wiring Regulations allow for a variation of 0-20% on the test voltage, but do you really want to be carrying out a 500 V test at just 400 V or, even possibly worse, at as much as 600 V!

In fact, for many years the best insulation testers have displayed the test voltage at the same time as the measured insulation resistance value. This is a useful feature, but you still have to remember to check the voltage. The very latest testers, however, provide an even more convenient solution – measured and regulated output voltage, ensuring a far tighter tolerance than anything seen previously. In fact, this is now controlled to +2%.

MIT400 series insulation testerFor some applications, variable test voltage is very useful. For example, when testing some types of electronic equipment, the manufacturer may specify that a particular voltage is to be used for insulation testing. With the best of the new generation test sets, this needn’t be a problem, as some models allow the test voltage to be adjusted in 1 V steps over a very wide range.

Another area of improvement is battery life. There are few things that are more inconvenient than having the batteries in your tester run out while you’re in the middle of checking an installation, so the extended battery life offered by the latest testers is a very useful feature.

Possibly even more useful is the option of using high capacity fast charging rechargeable cells. Not only are these a very convenient source of power, but over time they will also save a lot of money when compared with the cost of purchasing ordinary disposable batteries.

In addition, almost all insulation testers make provision for continuity testing. Here, a fast reaction time is always important, as even a delay of 100 milliseconds or so soon becomes annoying when carrying out a multiple continuity checks.

MIT400 series insulation tester charging adapterIt’s also useful for the instrument to offer testing at both 200 mA and 20 mA, to cater for the widest range of applications. In fairness, many of today’s testers already have this functionality, but the maximum circuit resistance for 200 mA testing is usually limited to 10 Ω. The most recent testers, however, allow 200 mA testing to be carried out in circuits with a resistance up to 20 Ω.

By now you may be thinking that it is time to replace your existing insulation tester and start enjoying the benefits of the most up-to-date models. But where can you find instruments that combine all of the features discussed with robust construction, convenience, ease of use and, of course, exceptional value for money? Actually, that’s not difficult – Megger’s recently introduced MIT400 Mk 2 insulation test sets deliver everything we’ve described and much more.

So if you want the latest and most reliable in electrical testing equipment, without compromising on performance or safety, get in touch with the Megger UK customer support team.

Tags: insulation, insulation test, insulation testers