Avometer

Avometer, also styled AVOmeter, is a British electrical-instrument brand best known for analogue multimeters. Its name derives from the three principal quantities represented in the original instrument—amps, volts and ohms—and the brand became sufficiently familiar in Britain that technicians often referred to a multimeter simply as an “AVO.” The product line originated in 1923, when the Automatic Coil Winder and Electrical Equipment Co. developed an instrument based on a concept associated with Donald Macadie, a Post Office engineer working in London. The first meter combined direct-current measurement, direct-voltage measurement and resistance measurement in one compact device. This integrated approach helped establish the multimeter as a practical service tool rather than a collection of separate laboratory instruments. The earliest Avometer used a rotary selector to choose its principal function and range. It was housed in a distinctive combination of wood, ebonite and aluminium. Within several years, the design was revised around a lower-current movement and a moulded insulating body, while the number of available ranges increased. Later generations added alternating-current capability, higher sensitivity and protective features. The 1931 Universal AVOmeter extended the instrument beyond direct-current work by using copper-oxide rectifiers, and subsequent designs expanded the range count through dual-sensitivity circuits and additional voltage and current options. Avometers were designed around straightforward operation. Many versions allowed the user to perform measurements through two main input terminals, with interlocking switches intended to prevent incompatible AC and DC selections. The instruments also incorporated mechanical or electrical protection against overload. Later models added cut-outs, fuses and, in some versions, an off position that both disconnected the terminals and damped or short-circuited the moving-coil movement. These features addressed practical problems encountered in workshops and in transport, including damage caused when earlier meters were left in an undamped switch configuration. The brand’s most recognized products were the Model 7 and Model 8. The Model 7 was developed as a high-sensitivity instrument for radio and electronics servicing, while the Model 8, introduced in 1951, became the best-known member of the range. Model 8 instruments were produced through seven marks and remained in manufacture until 2008. The line included versions with different high-voltage ranges, protection arrangements and compliance features. Some later variants were designed to meet NATO requirements and were issued to military services. Model 9 instruments offered a closely related design using international symbols, and the later Model 8 Mark V incorporated features associated with the Model 9. Avometers were widely used in British manufacturing, maintenance, research and development, education, utilities, government departments and the armed forces. Special instruments were made for customers including the British Admiralty, the Air Ministry and railway organizations. The range also covered automotive meters, compact AVOminor and Multiminor instruments, heavy-duty railway-oriented meters, clamp meters and other specialist equipment. The manufacturing business produced additional electrical instruments, including valve testers, and also made Geiger counters for civil-defence applications during the 1950s and 1960s. Although demand for traditional analogue instruments continued among some users, production of Avometers ended in 2008. The stated reason was increasing difficulty obtaining mechanical components. The final instrument to leave the factory was an AVOmeter Eight Mark 7, later presented by Megger in 2010. Megger now owns the Avometer trademark. The instruments remain significant both as historical test equipment and as collectible examples of British electrical engineering, and some continue to be used where their robust construction, analogue response and familiar operating characteristics are valued.

The Avometer story began in Britain in 1923 with the Automatic Coil Winder and Electrical Equipment Co. The instrument was conceived in connection with Donald Macadie, a Post Office engineer who sought a practical way to combine several electrical measurements in one device. The original meter measured direct current, direct voltage and resistance. It used a multi-position selector and a separate control arrangement, and its construction combined an oak case, an ebonite panel and an aluminium upper section. The initial design was revised after approximately three years of production. A new movement reduced the full-scale current requirement, and the instrument gained a larger set of ranges. The revised construction used a phenolic moulding and a deep-drawn aluminium rear case. A mirror and knife-edge pointer supported more reliable reading, while fuse and overload arrangements evolved as the series matured. The back of the case commonly carried operating information, a characteristic retained across later instruments. Alternating-current measurement was added through the Universal AVOmeter, introduced in 1931 after copper-oxide rectifiers became available. Further development produced expanded range sets and dual-sensitivity circuits. The Universal instruments were followed by Model 40 and by higher-sensitivity products aimed particularly at radio and electronics service work. The Model 7, introduced in the 1930s, offered substantially greater sensitivity than the general-purpose versions and became an important professional instrument. The Model 8 was introduced in May 1951 and ultimately appeared in seven marks. It combined broad current, voltage and resistance coverage with a sensitivity suitable for electronics work. Depending on the version, high-voltage ranges extended to 2,500 or 3,000 volts, although the highest ranges were removed from later variants as safety expectations changed. Later Model 8 versions also improved fuse protection and added an off position that helped protect the movement during storage and transport. Model 9 instruments were closely related but used international symbols rather than letter-based AC and DC markings; their features were later incorporated into the Model 8 family. The product family expanded beyond the principal models. The Model 12 targeted automotive work. AVOminor instruments provided smaller formats, while the AVO Multiminor offered rotary-switch selection in a more portable body. A heavy-duty version was first developed for railway signalling requirements and was later sold commercially. Clamp meters addressed higher-current work. The manufacturer also produced valve testers and Geiger counters, showing that its activities extended beyond multimeters. Avometers became common throughout British manufacturing and service industries, research laboratories, further and higher education, utilities, government organizations and the armed forces. Special versions were supplied to military and public-sector customers, including instruments made to Admiralty and Air Ministry requirements. Later Model 8 versions were designed around NATO specifications and were issued to NATO services. Technical manuals and service documentation frequently used Model 7 or Model 8 readings as reference points. The brand’s long production history ended in 2008. Continued demand was not enough to offset reported supply problems involving mechanical parts. A final Model 8 Mark 7 was subsequently presented in 2010 by Megger, which owns the Avometer trademark. Although no longer produced as a mainstream instrument line, Avometers retain a presence among collectors, restoration specialists and technicians who value the characteristics of traditional moving-coil analogue meters.

• 2010

  Final production meter presented

  [1]Avometeren.wikipedia.org

  Megger presented the final AVOmeter Eight Mark 7 in February 2010.

• 2008

  Model 8 production ends

  [1]Avometeren.wikipedia.org

  Production of Avometer instruments stopped, reportedly because sourcing mechanical parts had become increasingly difficult.

• 1951

  Model 8 introduced

  [1]Avometeren.wikipedia.org

  The Model 8 became the signature Avometer family and remained in production in successive marks until 2008.

• 1939

  Universal AVOmeter Model 40 introduced

  [1]Avometeren.wikipedia.org

  Model 40 developed the general-purpose Universal AVOmeter with expanded ranges and automatic cut-out features.

• 1936

  Model 7 generation begins

  [1]Avometeren.wikipedia.org

  The high-sensitivity 50-range Universal AVOmeter, later known as Model 7, entered the range for radio and electronics servicing.

• 1935

  AVOminor introduced

  [1]Avometeren.wikipedia.org

  The smaller AVOminor was introduced for direct-current, direct-voltage and resistance measurements.

• 1931

  Universal AVOmeter adds AC measurement

  [1]Avometeren.wikipedia.org

  The Universal AVOmeter introduced alternating-current and alternating-voltage capability using copper-oxide rectifier technology.

• 1926

  United States patent follows earlier European filings

  [1]Avometeren.wikipedia.org

  The Avometer concept received a United States patent after earlier patent filings in Czechoslovakia, Austria, France, Germany and Switzerland.

• 1923

  First Avometer introduced

  [1]Avometeren.wikipedia.org

  The first Avometer was made by the Automatic Coil Winder and Electrical Equipment Co. and combined direct-current, direct-voltage and resistance measurement.

Historically positioned as a dependable, versatile and easy-to-use professional measuring instrument for industrial maintenance, electronics servicing, education, utilities and military applications. The brand emphasized broad measurement capability, mechanical robustness, analogue readability and practical protection features.

• General-purpose analogue multimeter · 1923

  The AVOmeter

  The original 1923 instrument measured direct current, direct voltage and resistance. It used a single selector to choose function and range and was built in a distinctive wood, ebonite and aluminium enclosure. Its design established the integrated measurement format that defined the later Avometer family.

• General-purpose analogue multimeter · 1939

  Universal AVOmeter Model 40

  Model 40 was a development of the Universal AVOmeter, with AC and DC capability, broad current and voltage ranges, and automatic cut-out protection. It served general industrial and service applications and remained available for decades.

• High-sensitivity electronics multimeter · 1936

  AVOmeter Model 7

  Model 7 evolved from the high-sensitivity 50-range Universal AVOmeter and was intended principally for radio and electronics servicing. Its sensitivity and optional accessories made it suitable for detailed electrical testing beyond basic industrial measurements.

• Professional analogue multimeter · 1951

  AVOmeter Model 8

  Introduced in 1951, Model 8 was the best-known Avometer family. Across seven marks it offered AC and DC voltage and current ranges, resistance measurement, high sensitivity and progressively improved overload and fuse protection. Later versions were designed with contemporary safety and NATO requirements in mind.

• Professional analogue multimeter

  AVOmeter Model 9

  Model 9 was closely related to Model 8 but used international symbols instead of letter markings for its AC and DC controls. It included high-voltage capability in its principal configuration and was eventually superseded as Model 8 incorporated related features.

• Automotive multimeter

  AVOmeter Model 12

  Model 12 was designed for automotive testing. Its range structure addressed vehicle-related voltage and current measurements, with accessory shunts extending current capability for particular applications.

• Compact analogue multimeter · 1935

  AVOminor and Universal AVOminor

  The AVOminor family provided smaller instruments than the main Avometer models. The original AVOminor focused on DC and resistance functions, while the Universal version added AC capability selected through dedicated sockets.

• Portable analogue multimeter

  AVO Multiminor

  The AVO Multiminor replaced the earlier Minor instruments with a compact meter using a rotary selector for its functions and ranges. It was intended as a portable alternative for lower-current and general electrical testing.

• Rugged industrial multimeter · 1948

  Heavy Duty AVOmeter

  The Heavy Duty AVOmeter was developed in response to railway signalling requirements and was first supplied after the Great Western Railway had become part of British Railways. Its rugged construction and industrial range set later supported commercial use.

• Clamp meter

  AVO clamp meter

  The Avometer clamp meter addressed higher-current AC measurements without requiring the conductor to be disconnected. Its published range included current capacities up to 1,200 amperes together with several AC voltage ranges.

• Electronic test instrument

  AVO valve testers

  The manufacturing company associated with Avometer produced valve, or vacuum-tube, testers alongside its multimeters. These instruments supported testing and servicing of electronic valves during the period when vacuum-tube equipment was widely used.

• Radiation measuring instrument

  AVO Geiger counters

  The company also manufactured Geiger counters for civil-defence applications during the 1950s and 1960s. They represented an adjacent measurement-instrument activity rather than the core multimeter range.

• 2008

  End Avometer productionStrategy

  Background

  Traditional analogue instruments continued to have users, but the manufacturer reportedly faced increasing difficulty obtaining mechanical components.

  Action taken

  Production of the Avometer line was stopped, ending the manufacturing run of the Model 8 Mark 7.

  Aftermath

  Avometers continued primarily as legacy, collectible and specialist instruments, while the trademark remained owned by Megger.

  Source

• 1951

  Introduce the Model 8Product launch

  Background

  Avometer required a high-sensitivity professional instrument capable of serving electronics technicians and other users who needed a broad set of analogue measurement ranges.

  Action taken

  The company launched the Model 8, which became the central product family and was developed through seven successive marks.

  Aftermath

  Model 8 became the most widely recognized Avometer model and remained in production for more than five decades.

  Source

• 1931

  Expand the range with the Universal AVOmeterProduct launch

  Background

  The original and early revised Avometers were primarily DC instruments. The availability of copper-oxide rectifiers created an opportunity to add alternating-current and alternating-voltage measurement.

  Action taken

  The company introduced the Universal AVOmeter and subsequently expanded its range count through dual-sensitivity circuitry.

  Aftermath

  The Universal design broadened the brand's usefulness across industrial maintenance, radio servicing and electrical education.

  Source

• 2010

  Final AVOmeter Eight Mark 7 presented by Megger[1]Avometeren.wikipedia.org

  Other

  The last meter to leave the factory was an AVOmeter Eight Mark 7, which Megger presented to the winner of a company competition in February 2010.

• 2008

  Production of Avometer instruments ends[1]Avometeren.wikipedia.org

  Other

  Manufacture of the Avometer range ended after reported difficulties obtaining mechanical components. The Model 8 Mark 7 was the final major production version.

1. 1Avometeren.wikipedia.org