April 2020
The Man Behind the Insulation Tester

The Man Behind the Insulation Tester

20 April 2020

When you google “Sydney Evershed” the first thing that pops up is Sir Sydney Herbert Evershed an English brewer and cricketer – quite the combination of talents, but not the man we were looking for.

The next Sydney Evershed is an English brewer and politician. Again, weird combination, but apparently a popular profession in the late 1800s!

Still, not the guy we’re looking for though.

Don’t lose hope though – there’s still more things to click on.

And there it is – the third listing down – Sydney Evershed, English electrical engineer, inventor, and co-founder of Evershed and Vignoles. It’s about time.

The Father of Insulation Test Equipment

In 1889, the Mr. Evershed, not a brewer nor a cricket player nor a politician, but the father of insulation test equipment invented the insulation tester.

Big thanks to this man, right?

We’re still not sure why his rank on Google is so bad. But it’s okay – we’re over it now.

Evershed was a pretty big figure in the UK electrical industry back in his day – serving as the Vice-President of the Institution of Electrical Engineers (IEEE) from 1924 to 1925.

Unexpectedly, he had no formal education, as he spent most of his time helping his Dad with his “tanning” business – manufacturing tanning oil to turn animal hide into leather.

Regardless, he was excited by electricity, and particularly in-awe of incandescent electric lamps used for street lighting.

At the same time, he was disappointed – to say the least – in the quality of installation work of these electric cables.

So, how did he get into the electrical industry?

From manufacturing tanning oil to manufacturing test equipment – sounds like a tricky career switch, right? Well, not for Evershed. In 1885, he became the manager at Goolden and Trotter – a London manufacturer of hot wire voltmeters.

From there, he really started making some pretty big career moves, so listen carefully.

We don’t have all the details – since it was the late 1800s and people weren’t tweeting, posting Facebook statuses, or taking photos every 10 seconds – but we’re taking an educated guess that Evershed was climbing the proverbial corporate ladder. Additionally, he wasn’t wasting his free time watching Netflix (or whatever people did for fun in the late 19th century), he was learning electricity, experimenting with electrical equipment, and inventing new measuring instruments.

In 1895, Evershed and his assistant E B Vignoles purchased Goolden and Trotter’s instrument department – renaming it Evershed and Vignoles.

But what about the insulation tester?

We’re getting to that part of the story – patience, please.

By the way, the instrument industry was just starting to take off, as a relatively new branch of engineering, and a new batch of inventors were beginning to take the stage.

So, at this point in time, many were already testing insulation by applying a low voltage and detecting the resulting current flow with a galvanometer. Unfortunately, as pointed out by Mr. Evershed, there were quite a few issues with this method.

Not only was it difficult to apply in the field, but at such a low voltage, this method failed to identify insulation issues that would present themselves when the circuit was in it’s normal working voltage environment.

This was just the motivation Evershed needed to create something better – the world’s first megohmmeter. Using a hand-crank generator, the megohmmeter made insulation resistance measurements at a voltage comparable with the normal working voltage of the unit under test.

In 1903, under the registered trademark “Megger”, Evershed’s invention took the market by storm.

The insulation tester you know (and love) today is a direct descendant of the very first megohmmeter. How neat is that?

Did Evershed do anything else?

Yes, of course! Despite Google’s lack of acknowledgement towards Evershed, he was also interested in magnets and he wrote – get this – a 130-page paper titled “Permanent Magnets in Theory and Practice”, which he presented to IEE.

Evershed & Vignoles later became Megger, as you know it today. If you’re interested in learning more about that history and the evolution of Megger, we’ve got all those details here.

And there you have it – the man behind the insulation tester.

What now?

Well, insulation testing has definitely taken off, since that original invention. While instruments have evolved with sleeker exteriors, technology has improved, and testing capabilities have grown, the theory has remained the same – thanks to good ole Sydney Evershed.

Following in Evershed’s footsteps, Megger continues to be at the forefront of electrical testing and education – especially when it comes to insulation resistance testing. With hundreds of products on the market, numerous test methods to choose from, and endless applications, getting started can be a challenge, but we’re here for you! View our latest webinar - Fundamentals of IR Testing - or check out our Guide to Insulation Resistance Testing

To view our range of insulation testing products, please visit -

Tags: electrical, electrical equipment, electrical testing, insulation, insulation resistance testing, insulation tester, insulation testing, IR testing