The story
Over the years there were several companies whose names were associated with Megger.
Evershed & Vignoles
Sydney Evershed (1858–1939) and Ernest Vignoles (1865–1948) bought the instrument section of Golden Trotter (where they both worked) and founded Evershed & Vignoles Limited on 5 February 1895. However, it is likely that the origins of Megger can be traced back to 1889. The company was based at Acton Lane Works, Acton Green, London, where it moved from Westbourne Park in 1903.
Sydney Evershed applied for several patents for various electric devices. One of them was for a "hand dynamo", which allowed the generation of voltages high enough to measure resistance in the megohm range and facilitated the construction of the first portable insulation tester. The Megaohm Meter was then named the Megger, and the word became a trademark name, registered on 25 May 1903. The invention became a popular method of insulation testing and, by the 1920s, it was "well-known" by other engineers.
Due to electromagnetic interference, the first Megger insulation testers were built as two separate boxes – one for voltage generation, and one for measurement. They were later integrated into a single device in a Bakelite case, with special foldable handle for driving the dynamo. The most popular was the so-called "Wee Megger" (voltage up to 500 V and resistance up to 20 megohms), but there were larger devices like the "Major Megger", "Meg", or "Megger insulation tester", which could generate up to 2500 V and measure resistance up to 20,000 megohms. The modern version of Megger – model MJ15 – can generate up to 5 kV.
In the 1920s, the company employed approximately 500 people. That number rose to 1,000 during the Second World War, reaching its peak of 1,870 in 1967.
In 1965, Evershed & Vignoles Ltd. became a part of the George Kent Group.
H.W. Sullivan Ltd
The company (established in 1922) was producing precision laboratory equipment (e.g. resistors, inductors, shunts, galvanometers, etc.). H.W. Sullivan Ltd was incorporated into Megger in 2002.
AVO
The invention of the first multimeter is attributed to Donald Macadie (1871–1955) who was the manager of the Post Office Telephone Factory in Holloway, North London. He was granted Patent GB 200977 on 26 July 1923. It has often been stated that Mr. MacAdie devised the Avometer because he became dissatisfied with having to carry many separate instruments required for the maintenance of the telecommunication circuits. This story may be based on a paper "The History of the Avometer" by PR P Hawes. However the accuracy of the story may be questioned because it is unlikely that a senior Post Office Engineering manager would have been carrying around his own instruments. Macadie invented a first instrument, which could measure Amps, Volts and Ohms, so the multifunctional meter was then named as AVO.
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The Automatic Coil Winder and Electrical Equipment Company (ACWEECO,)was formed in 1922, principally by R H Rawlings, to exploit both the Avometer patent and that for an automatic coil winder also designed by MacAdie (GB199417). The first AVO was put on sale in 1923, and although it was initially a DC-only instrument many of its features remained almost unaltered right through to the last Model 8.
ACWEECO later became known as AVO Limited and manufactured instruments with the AVO trademark.
Instruments derived from the original AVO multimeter were manufactured continuously from 1923 until the final model (AVO Model 8 Mk 7) was made in October 2008. Its production was terminated only due to increasing problems with obtaining some mechanical parts for the movement. The AVO Model 8, a 20,000 ohm per volt universal instrument, was introduced in 1951 and versions of this model were extensively used, especially in British industry, education and research, for 57 years without major modifications to the functions it provided.
With the intention of promoting export sales, Avo produced several other types of multimeter (Models 10, 14, 15, 16 and 20/21), which might be considered more modern in design than their traditional types but considered the British market more conservative and, initially at least, these instruments were not offered on the home market. The Model EA113 was an excellent electronic multimeter, sold in the UK and abroad, in the same style as the Model 14 to 21 range.
Avometer model numbers were first used by the company from 1936 (Avometer Model 7) and were used to distinguish designs with different ranges and functionality. Several "Models" were in production contemporaneously. Some designs were produced especially for specific industries (e.g. Model 12 for Auto-electrical work) and at the request of large companies, the British armed forces and later NATO.
The company also designed and made other electronic instruments such as signal generators, valve (vacuum tube) testers and valve characteristic meters and specialist equipment for radio servicing. Many of these were intended for both military and commercial use and were made to a very high standard.
AVO Training Institute
In 1963 Multi-Amp and AVO created Multi-Amp Institute. In 2004 the Institute became AVO Training Institute, Inc. with the headquarters in Dallas, Texas. AVO Training Institute was established for providing training in electrical engineering, particularly regarding safety, maintenance and testing of electrical equipment, also by using instruments from competitive manufacturers.
In 1996 the Institute was certified with ISO 9001 and so far over 230,000 electrical maintenance and testing technicians and engineers from around the world have attended training courses.
The Institute has a Technical Resource Center – an online store offering books, standards, training materials, Personal Protective Equipment, and tools.
The actual training can be organised in different sites around the world, for example at the Megger facility in Paris.
The AVO Electrical Engineering Division was created in 2002 and it specialises in power system studies, specifically arc flash hazard analysis.
Thorn Electronics/EMI
In 1970, along with other members of the George Kent Group the company was acquired by Thorn Electrical Industries founded in 1936.
The company was taken over by Thorn EMI in 1967 (linked with company EMI), which at the same time also bought AVO Limited.
In 1987 the name of the company was for the first time changed to Megger Instruments Limited.
From Wikipedia’s article on Megger, shared under CC BY-SA 4.0.5