Automatic Coil Winder and Electrical Equipment Co.
Wellington House, Buckingham Gate, London, SW1 (1923)
Winder House, Douglas St, London SW1. (1939)
Avocet House, 92-96 Vauxhall Bridge Road, London SW1 (1953)

Avo Ltd.
Avocet House, 92-96 Vauxhall Bridge Road, London, SW1 (1957)
Archcliffe Road, Dover, Kent CT17 9EN (1967)

Megger Instruments Ltd.
Archcliffe Rd, Dover, Kent CT17 9EN (1987)

AVO Megger Instruments Ltd.
Archcliffe Rd, Dover, Kent CT17 9EN (1991)

AVO International Holdings Ltd.
Archcliffe Rd, Dover, Kent CT17 9EN (2000)

AVO International Ltd.
Archcliffe Rd, Dover, Kent CT17 9EN (2002)

Megger Group Ltd.
Archcliffe Rd, Dover, Kent CT17 9EN. (2024)

AVO, founded in 1923 as the Automatic Coil Winder and Electrical Equipment Company (ACWEECO), revolutionised electrical measurement with the introduction of the first Avometer. This multimeter measured direct voltage, current, and resistance. The company expanded rapidly, relocating several times to accommodate growth.

During World War II, AVO doubled its workforce and produced crucial electrical instruments for the war effort. The iconic Model 8 Avometer was launched in 1951, becoming a staple in the industry. Over the decades, AVO underwent several name changes and acquisitions, including becoming part of the Thorn Group in 1967. In 1987, it became Megger Instruments Limited after a management buyout.

The company continued to innovate and expand its product range, maintaining its position as a leader in electrical measurement technology until the present day.

Founding and Early Days

1922: The Automatic Coil Winder and Electrical Equipment Company (ACWEECO) was formed, primarily by R H Rawlings, to exploit both the Avometer patent and that for an automatic coil winder designed by Donald Macadie.

May 23, 1923: ACWEECO was officially registered as a private company with a capital of £10,000 in £1 shares. The company's purpose was to acquire from S. H. Rawlings the benefit of certain existing inventions relating to an automatic coil winding machine and an instrument for registering electrical current and resistances, to be called an "Avometer".

The first directors were:

• F. B. Larkworthy (chairman)
• S. H. Rawlings
• F. C. G. Larkworthy

The registered office was at 9, Victoria Street, S.W.1. [1]

May 23, 1923: H Rawlings made an Application for the Avometer No 427,638, Class 8, trademark. [2]
1923: The first Avometer was put on sale. It was initially a DC-only instrument that measured direct voltage, direct current, and resistance.

Expansion and Innovation

1927: The factory moved to new premises at Winder House, Rochester Row, London SW1.
1930: The factory relocated again to Winder House, Douglas St, London SW1.
1933: The Universal model was introduced, adding AC measurement capabilities.
1936: The Model 7 was introduced with an exceptional 1,000 ohm per volt DC sensitivity.
1939: The factory expanded to new premises at AVOCET House 92/96 Vauxhall Bridge Road, London SW1.

World War II Effort

During World War II, the Automatic Coil Winder and Electrical Equipment Company (ACWEECO) significantly contributed to the war effort by:

1. Increasing production: The company expanded its workforce from approximately 500 people before the war to 1,000 during World War II.  This increase in manpower allowed for greater production of essential electrical equipment.
2. Manufacturing critical instruments: ACWEECO continued to produce its flagship product, the AVO meter, which was crucial for electrical and electronic work in various military applications. The company also designed and manufactured other electronic instruments such as signal generators, valve (vacuum tube) testers, and valve characteristic meters.
3. Producing specialized equipment: ACWEECO developed and manufactured specialist equipment for radio servicing, intended for both military and commercial use. These instruments were made to very high standards, suitable for wartime requirements.
4. Supporting military operations: The company's instruments, particularly the AVO meters, were likely used in various military contexts, including the maintenance and repair of electrical and communications equipment essential for the war effort.

While specific details about ACWEECO's wartime production are limited, the company's expansion and focus on high-quality electrical instruments undoubtedly played a significant role in supporting the United Kingdom's technological and industrial needs during World War II.

Post-War Developments

1951: The first AVO Model 8 was launched in May, which would become one of the best-known multimeters of the range.
1957: The company became public and was renamed Avo Ltd. [3]
1958: Avo Ltd acquired Taylor Electrical Instruments Ltd of Slough.
1959: Metal Industries Ltd acquired Avo Ltd, including its subsidiary Taylor Electrical Instruments Ltd.

Expansion and Acquisitions

1962: The company acquired land in Dover for a new factory.
1964-1966: The factory on Vauxhall Bridge Rd and the new factory at Archcliffe Rd, Dover, Kent ran in parallel. By 1966, production had fully moved to the Dover factory.
1967: Thorn Electrical Industries took over Metal Industries, and AVO Ltd became part of the Thorn Group of Companies.
1972: H W Sullivan, another member of the Thorn group, was incorporated into AVO Ltd.
1986: AVO Ltd acquired part of Evershed and Vignoles Ltd.

Corporate Restructuring

1987: After a management buyout, the name changed to Megger Instruments Limited.
1991: The company changed its name to AVO Megger Instruments Limited. In the same year, the Thyssen Bornemisza Group took over the company along with Biddle (USA) and others.
2000: The company became known as AVO International Holdings Limited.
2002: The name changed to AVO International Ltd.

Recent History

2008: The last version of the Model 8 (Mark 7) was produced, ending a 57-year production run.

Present day: The company is now part of the Megger Group, with the UK branch remaining at Archcliffe Rd, Dover, Kent.

Throughout its history, the Avometer and its parent companies have been at the forefront of electrical measurement technology, continuously innovating and adapting to changing market needs. The Avometer's basic design principles, established in the 1920s, remained influential in multimeter design for decades, a testament to the ingenuity of its original concept.

Macadie History;

Donald Macadie (1871-1955) played a pivotal role in the development of the Avometer and the subsequent formation of the Automatic Coil Winder and Electrical Equipment Company (ACWEECO). Here's how he fits into the detailed history:

Early Career and Invention

Donald Macadie was a British Post Office engineer who, in 1920, became frustrated with carrying multiple separate instruments for his work on telecommunication circuits.

This frustration led him to invent the world's first true multimeter, which he called the Avometer (derived from Amps, Volts, and Ohms).

Key Contributions

• Conceptualization and Design: Macadie designed a single portable device that could measure direct current, direct voltage, and resistance.
• Patent: He patented his innovative design for the multimeter..
• Naming: Macadie coined the term "AVOmeter" for his invention.

Commercialization and Company Formation

In 1923, the Automatic Coil Winder and Electrical Equipment Company (ACWEECO) was founded to manufacture Macadie's inventions. The company produced not only the Avometer but also an automatic coil winding machine, another of Macadie's patented inventions.

Continued Involvement

Despite being a shareholder in ACWEECO, Macadie continued to work for the Post Office until his retirement in 1933. After retirement, he devoted considerable time to the activities of ACWEECO..

Legacy and Later Life

1. Family Involvement: Macadie's son, Hugh S. Macadie, joined ACWEECO in 1927 and became Technical Director.
2. Recognition: Donald Macadie was awarded an MBE (Member of the Order of the British Empire) for his contributions.
3. Passing: Macadie died in 1955 at the age of 83, leaving behind a legacy that transformed electrical measurement technology.

The Avometer that Macadie invented went on to become one of the most recognized and widely used multimeters in the industry, with various models produced over several decades. His invention laid the foundation for modern multimeters and significantly impacted the field of electrical measurement.

[1] The Electrical Review Jun 1, 1923, Page 866.
[2] The Electrical Review Jun 1, 1923, Page 858.
[3] The Electrical Review Jun 5, 1957, Page 20.