Keith Wilson - Electrical engineer
There’s no doubt that Sydney Evershed was a genius. He invented the first practical insulation tester – “the Megger” – and thereby made possible the safe installation and working of electrical distribution systems. In the early years of the twentieth century, he was one of the most eminent figures in the UK electrical industry, serving as Vice-President of the Institution of Electrical Engineers (the IEE, now the IET) from 1924 to 1925.
Yet if someone were to apply for a job with Megger today, having the same qualifications that Evershed held as a young man, it is unlikely they would even get an interview. That’s because Evershed had no qualifications. He had little formal schooling and his obituary in The Engineer reports that “he never passed an examination nor even attempted to do so”!
Evershed’s father was a tanner – someone who processes animal hides to turn them into leather – and, because of problems in his father’s business, Evershed spent most of his early years manufacturing tanning oil rather than attending school. Nevertheless, he always took a keen interest in electricity and, in an article he wrote for the Jubilee issue of the Journal of the IEE, he recalls a visit he made in 1881 to Godalming, the first town in England to have a public electricity supply.
He mentions being much impressed by Swan’s incandescent electric lamps (though American readers might consider them to be Edison’s), which were used in the town’s street lighting. He was less impressed by the quality of the installation work, noting “the cables were laid in the gutter, with nothing but their innocence to protect them from the wheels of carts or the hoofs of cart horses.” Maybe this was the observation that spurred his interest in finding ways to improve the safety of electrical installations?
Be that as it may, just four years later in 1885 Evershed successfully applied for the post of manager at Goolden and Trotter, a London company engaged among other things in the manufacture of Cardew hot-wire voltmeters. In 1895, in conjunction with his assistant E B Vignoles, Evershed purchased the company’s instrument department and renamed it Evershed and Vignoles Ltd.
Evershed was one of the first to realise that the methods of testing insulation then in use, which involved applying a low voltage and detecting the resulting current flow with a sensitive galvanometer, had serious limitations. This technique was not only difficult to apply in the field but also fundamentally unsatisfactory as it failed to reveal problems that might show themselves when the circuit was subjected to its normal working voltage.
As a result, he developed the world’s first direct-reading megohmmeter. Energised by a small hand-cranked generator, this revolutionary instrument made measurements at a voltage comparable with the normal working voltage of the circuit under test. The first versions became available in 1889 and by 1903 they were being sold as Megger insulation testers. These groundbreaking instruments are the direct antecedents of every insulation tester in use in the world today.
While Evershed is, with good reason, best remembered for his work relating to insulation and insulation testing, he also had a lifelong interest in magnets and magnetic materials. Just a few years before his retirement in 1923, he presented a two-part paper to the IEE with the title Permanent Magnets in Theory and Practice.
Since this paper runs to over 130 pages, it’s impossible to even summarise the content here, but its clear that Evershed felt that work was needed in relation to the manufacture of permanent magnets as, in his introduction, he states, “It would be hard to find a manufacture more entangled in occult molecular phenomena”, which doesn’t sound like a resounding vote of confidence!
Evershed was, according to his IEE obituary, which appears to have been written by E B Vignoles, “full of quaint quips and odd humour”. It has to be said that this is open to a wide range of interpretations. He died in September 1939, but the company that he and E B Vignoles founded lives on and continues to thrive as the very successful Megger Group.
The world should be grateful to Sydney Evershed for making electricity safer to use, and it would be fitting for those of us who work in the electrical industry to remember his name from time to time when we hit the “test” button on our insulation test set – or, indeed, crank the handle!
Electrical Tester would like to thank the IET Archive Department for providing the material on which much of this article is based.