
Megger Group Limited (also known as Megger) is a British manufacturing company that manufactures electronic test equipment and measuring instruments for electrical power applications.
Megger is known for its
electrical insulation
Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...
testers. It supplies products related to the following areas:
cable
Cable may refer to:
Mechanical
* Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof
* Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
fault locating,
earth/ground testing, low
resistance measuring,
power quality
Electric power quality is the degree to which the voltage, frequency, and waveform of a power supply system conform to established specifications. Good power quality can be defined as a steady supply voltage that stays within the prescribed range, ...
, electrical wiring, insulation testers,
multimeter
A multimeter (also known as a multi-tester, volt-ohm-milliammeter, volt-ohmmeter or VOM, avometer or ampere-volt-ohmmeter) is a measuring instrument that can measure multiple electrical properties. A typical multimeter can measure voltage, elec ...
s,
portable appliance testers, clamp-on meters,
current transformer
A current transformer (CT) is a type of transformer that reduces or multiplies alternating current (AC), producing a current in its secondary which is proportional to the current in its primary.
Current transformers, along with voltage or poten ...
s, etc.
History
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
Acton Green is a residential neighbourhood in Chiswick and the London Borough of Ealing, in West London, England. It is named for the nearby Acton Green common. It was once home to many small laundries and was accordingly known as "Soapsuds Is ...
, 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
A trademark (also written trade mark or trade-mark) is a form of intellectual property that consists of a word, phrase, symbol, design, or a combination that identifies a Good (economics and accounting), product or Service (economics), service f ...
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
Bakelite ( ), formally , is a thermosetting polymer, thermosetting phenol formaldehyde resin, formed from a condensation reaction of phenol with formaldehyde. The first plastic made from synthetic components, it was developed by Belgian chemist ...
case, with special foldable handle for driving the
dynamo
"Dynamo Electric Machine" (end view, partly section, )
A dynamo is an electrical generator that creates direct current using a commutator. Dynamos employed electromagnets for self-starting by using residual magnetic field left in the iron cores ...
. 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
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, 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
A multimeter (also known as a multi-tester, volt-ohm-milliammeter, volt-ohmmeter or VOM, avometer or ampere-volt-ohmmeter) is a measuring instrument that can measure multiple electrical properties. A typical multimeter can measure voltage, elec ...
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.
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
Dallas () is a city in the U.S. state of Texas and the most populous city in the Dallas–Fort Worth metroplex, the List of Texas metropolitan areas, most populous metropolitan area in Texas and the Metropolitan statistical area, fourth-most ...
,
Texas
Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
. 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
The ISO 9000 family is a set of international standards for quality management systems. It was developed in March 1987 by International Organization for Standardization. The goal of these standards is to help organizations ensure that they meet ...
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
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
.
The AVO Electrical Engineering Division was created in 2002 and it specialises in power system studies, specifically
arc flash
An arc flash is the light and heat produced as part of an arc fault (sometimes referred to as an electrical flashover), a type of electricity, electrical explosion or discharge that results from a connection through air to ground or another vol ...
hazard analysis.
Thorn Electronics/EMI
In 1970, along with other members of the George Kent Group the company was acquired by
Thorn Electrical Industries
Thorn Electrical Industries Limited was a British electrical engineering company. It was listed on the London Stock Exchange, but merged with EMI Group to form Thorn EMI in 1979. It was de-merged in 1996 and became a constituent of the FTSE 100 ...
founded in 1936.
The company was taken over by Thorn EMI in 1967 (linked with company
EMI
EMI Group Limited (formerly EMI Group plc until 2007; originally an initialism for Electric and Musical Industries, also referred to as EMI Records or simply EMI) was a British transnational conglomerate founded in March 1931 in London. At t ...
), 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.
Present times
Megger
Megger Instruments Limited was based at AVO's Dover site, in Archcliffe Road, Dover, CT17 9EN, Kent, England, which is also the present location of the UK branch of the company.
In 1991, the company changed its name to AVO Megger Instruments Limited. In 2000 the company became known as AVO International Holdings Limited and in 2002 as AVO International Limited.
Finally it changed its name to Megger Group Limited in 2002, as it is known today.
The Dover site employs around 230 people.
In total (including the sales channels) Megger Group Limited employs around 1500 people worldwide.
Biddle
For many years, the James G. Biddle Company in
Pennsylvania
Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...
, was the United States importer of Megger products, as well as a manufacturer of equipment under their own name. In 1989, using concepts introduced by
Commonwealth Edison Company
Commonwealth Edison, commonly known by syllabic abbreviation as ComEd, is the largest electric utility in Illinois, and the primary electric provider in Chicago and much of Northern Illinois. Its service territory stretches roughly from Iroquoi ...
of
Chicago
Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...
, Biddle started development of a range of equipment to test the integrity of large
battery systems, which led to the BITE (Battery Impedance Test Equipment) line of products.
In 1991 Biddle, Megger and MultiAmp joined together to form AVO International. The use of the Biddle trademark was retained for many of products still available today. Biddle was one of the first companies to provide commercial cable fault locators.
States
Megger Group Ltd. owns the US site in
Dallas
Dallas () is a city in the U.S. state of Texas and the most populous city in the Dallas–Fort Worth metroplex, the List of Texas metropolitan areas, most populous metropolitan area in Texas and the Metropolitan statistical area, fourth-most ...
,
Texas
Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
. They manufacture terminal blocks and test switches under the trademark States (existing since the 1940s).
PowerDB
PowerDB was acquired in autumn 2005. They provide "acceptance and maintenance test data management software" which is compatible with many Megger products.
Programma
Programma Electric AB was a
Swedish electrical test and measurement equipment manufacturer founded in 1976.
It provided products including: circuit breaker analysers, battery load testers, primary injection testers,
vacuum interrupter testers,
micrometers
The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...
and
protective relay test instruments. The production plant facility was located in
Täby
Täby () was previously a trimunicipal locality, with 76,700 inhabitants in 2024. However, as from 2016, Statistics Sweden has amalgamated this locality with the Stockholm urban area. It is the seat of Täby Municipality in Stockholm County, Sw ...
, Sweden.
In March 2001 Programma was sold to
GE Energy
GE Power (formerly known as GE Energy) was an American energy technology company owned by General Electric (GE). In April 2024, GE completed the spin-off of GE Power into a separate company, GE Vernova. Following this, General Electric ceased t ...
and joined Megger Group Ltd. in June 2007
as Megger Sweden AB. The company was relocated in April 2013 from Täby to
Danderyd
Danderyd Municipality (; ) is a municipality north of Stockholm in Stockholm County in east central Sweden. It is one of the smallest municipalities of Sweden, but the most affluent. Its seat is located in Djursholm and it is located within Sto ...
.
Pax Diagnostics
In October 2008 Megger Group Ltd. acquired Pax Diagnostics in Sweden. Pax manufactures
transformer
In electrical engineering, a transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple Electrical network, circuits. A varying current in any coil of the transformer produces ...
testing and insulation diagnostics equipment. Pax Diagnostics was founded in 2004 by former employees of Programma Electric, and it is also based in Täby.
SebaKMT
In July 2012 Megger acquired SebaKMT specialising in power cable fault location and testing, and pipe leakage detection.
[Electrical Digest / Megger acquires SebaKMT](_blank)
/ref>
SebaKMT has main development and manufacturing sites in Germany and the USA. This acquisition meant substantial increase of Megger's turnover. As a result, the Group's position on the market of test equipment for the electrical power sector increased significantly.
/ref>
SebaKMT developed and introduced the arc-reflection method for testing electrical faults in cables.
Baker Instrument
The business was acquired by Megger from the SKF Group on 19 August 2018. The UK test equipment manufacturer Megger Group has entered into agreement with SKF to purchase its Baker Instrument business which makes equipment for testing and diagnosing electric motors and other rotating machines. The terms of the deal have not been disclosed.
SKF acquired Baker for $14m in 2007. At that time, the Colorado-based business employed 62 people and had annual sales of around $11m. SKF said that the move into motor diagnostics was important to its energy efficiency business, and was in line with its move to support its customers sustainability efforts.
In 2018, SKF sold the Baker factory to the world leader Megger. This was a leverage to the Baker factory who are still the leaders on the market. There are many companies trying to copy their software for Surge test diagnostic, but they failed their tests.
Megger's CEO Jim Fairbairn, says: “We are excited to acquire a recognized industry leader with equipment and online testing capability that will complement Megger’s product range. We look forward to working with the Baker team to drive continued growth and innovation.”
Intellectual property
Trademarks
The first trademark of the company, the name Megger was registered in 1903 and it remains the intellectual property
Intellectual property (IP) is a category of property that includes intangible creations of the human intellect. There are many types of intellectual property, and some countries recognize more than others. The best-known types are patents, co ...
of the Megger Ltd.
Most of the names and trademarks of the acquired companies are now owned by Megger Group Ltd. Apart from "Megger" itself, the best known ones are: AVO, Biddle, Biddle AVO, Biddle Megger, States, PowerDB, and recently Programma and Pax Diagnostics.
However, some of the names of the products are also protected: Megger, AVO, DLRO, MFT, MIT, MPRT, etc.
The Group publishes a copyright
A copyright is a type of intellectual property that gives its owner the exclusive legal right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, ...
ed but distributed for free quarterly magazine titled "Electrical tester" aimed at electrical engineers who might use products from the Megger range.
Patents
It is difficult to assess the actual number of patents, because some of them were obtained before acquired companies joined Megger Group. The original Megger insulation tester patent is over 100 years old.
The table shows a timeline of some typical devices introduced by Megger Group companies (not necessarily covered with patents). In recent years the company has also paid more attention to the ergonomics
Ergonomics, also known as human factors or human factors engineering (HFE), is the application of Psychology, psychological and Physiology, physiological principles to the engineering and design of products, processes, and systems. Primary goa ...
and design of their products.
Awards
In 2011 Megger's MFT1700 Multifunction Tester won the "Innovative Test & Measurement Product of the Year", at the Electrical Industry Awards. Three other products were also nominated: hand-held micro-ohmmeter
An analog ohmmeter
An ohmmeter is an electrical instrument that measures electrical resistance (the opposition offered by a circuit or component to the flow of electric current). Multi-meters also function as ohmmeters when in resistance-meas ...
MOM2 (category Innovative Power Product of the Year), professional portable appliance tester PAT400 (Innovative Test & Measurement Product of the Year), and digital earth clamps DET14C / DET24C (Innovative Commercial/Industrial Product of the Year).
Megger also won in earlier editions, for instance in 2007 these were: multifunction tester MFT 1553 and portable cable fault location PFL40.
In 2012 Megger won an award for its TDR1000/3 time-domain reflectometer
A time-domain reflectometer (TDR) is an electronic instrument used to determine the characteristics of electrical lines by observing reflected pulses. It can be used to characterize and locate faults in metallic cables (for example, twisted pai ...
.
Products
Manufacturing
Megger Group has manufacturing sites and sales centres in several countries worldwide. The main production sites are in: Dover, Dallas, Valley Forge and Danderyd.
Certificates of Conformity are supplied with most instruments. Depending on product and site the metrology
Metrology is the scientific study of measurement. It establishes a common understanding of Unit of measurement, units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to stan ...
can be traceable to:
*ANSI/NCSL Z540-1
*Nuclear 10CFR Appendix B PART 21
*NIST
*MIL STD 45662-A
* ISO 10012
*ISO 17025
ISO/ IEC 17025 General requirements for the competence of testing and calibration laboratories is the main standard used by testing and calibration laboratories. In most countries, ISO/IEC 17025 is the standard for which most labs must hold accr ...
* National Physical Laboratory
Dover site has its own EMC laboratory and SMD machines. However, many of the mechanical parts are purchased from other suppliers. (This was one of the factors why production of AVO Model 8 was discontinued.)
All manufacturing sites have ISO 9001:2000 and Dover and Danderyd sites are certified to ISO 14001
The ISO 14000 family is a set of international standards for Natural environment, environment management systems. It was developed in March 1996 by International Organization for Standardization. The goal of these standards is to help organizations ...
.
Sales and technical support
The Group has over 1000 distribution points in 132 countries. 85% of sales are made via the distribution network. There are sales centres in several countries and products are also sold via specialised distributors including RS Components and more recently Test Equipment Connection Corporation.
There are total of 15 sales and technical support offices in the US, Canada, Dover, Paris
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
, Mumbai
Mumbai ( ; ), also known as Bombay ( ; its official name until 1995), is the capital city of the Indian state of Maharashtra. Mumbai is the financial capital and the most populous city proper of India with an estimated population of 12 ...
, Sydney
Sydney is the capital city of the States and territories of Australia, state of New South Wales and the List of cities in Australia by population, most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Syd ...
, and Bahrain
Bahrain, officially the Kingdom of Bahrain, is an island country in West Asia. Situated on the Persian Gulf, it comprises a small archipelago of 50 natural islands and an additional 33 artificial islands, centered on Bahrain Island, which mak ...
.
Types of products
Megger produces over 1000 products in around 25 groups:
#Battery test equipment
#Cable fault locating equipment
#Circuit breaker testers
#Data communication testers
#Fiber optic testers
#Ground resistance testers
#Insulation power factor testers
#Insulation resistance testers
#Line testing equipment
#Low resistance ohmmeters
#Motor and phase rotation testers
#Multimeters
#Oil testers
#Partial discharge test equipment
#Portable appliance and tool testers
#Power quality instruments
# Recloser test equipment
#Relay testers
#T1 network testers
#Tachometers and speed measurement instruments
# Time domain reflectometry testers
#Transmission impairment testers
#Watt-hour meter tester
#States terminal block and test switches
#Professional hands-on technical and safety training programs
The equipment is roughly divided into three groups: Power, Building and Wiring, and Telecommunications.
Research
In the UK, Megger regularly sponsors first year projects at the University of Kent
The University of Kent (formerly the University of Kent at Canterbury, abbreviated as UKC) is a Collegiate university, collegiate public university, public research university based in Kent, United Kingdom. The university was granted its roya ...
,
as well as collaborating with other universities.
Charity
Megger donated 5% of its Chinese sales revenue (for three months) to the local Red Cross after the 2008 Sichuan earthquake
An earthquake occurred in the province of Sichuan, China at 14:28:01 China Standard Time on May 12, 2008. Measuring at 8.0 (7.9–8.3 ), the earthquake's epicenter was located boxing the compass, west-northwest of Chengdu, the provincial ...
. This was also preceded with 15% reduction on all their equipment sold in China immediately after the earthquake.
Over $9,000 of electrical testing equipment has been donated to Mesalands Community College's North American Wind Research and Training Center (NAWRTC).
Megger donates equipment to NAWRTC
/ref>
References
External links
{{commons category, Megger
Megger Group Ltd.
Electronic test equipment manufacturers
Electronics companies of the United Kingdom
Manufacturing companies of the United Kingdom
Companies based in Kent
British brands