AVOmeter is a British trademark for a line of multimeters and electrical measuring instruments; the brand is now owned by the Megger Group Limited. The first Avometer was made by the Automatic Coil Winder and Electrical Equipment Co. in 1923, and measured direct voltage, direct current and resistance. Possibly the best known multimeter of the range was the Model 8, which was produced in various versions from May 1951 until 2008; the last version was the Mark 7. The multimeter is often called simply an AVO, because the company logo carries the first letters of 'amps', 'volts' and 'ohms'. The design concept is due to the Post Office engineer Donald Macadie, who at the time of the introduction of the original AVOmeter in 1923 was a senior officer in the Post Office Factories Department in London. Technical features The original AVOmeter was designed to measure direct current (3 ranges, 0.12, 1.2 & 12 A), direct voltage (3 ranges, 12, 120 & 600 V) and resistance (single range, 0 - 10,000 ohms, 225 ohms mid-scale). All ranges could be selected by a single rotary switch which set both the function and the range value. A second switch brought a rheostat into circuit in series with the instrument and could be used to control the current through a device under test and the meter. The movement drew 12 mA for full-scale deflection and used a "universal shunt" permanently in parallel with the movement which increased the input terminal full-scale current to 16.6 mA, corresponding to 60 ohms per volt. It had a knife edge pointer and an anti-parallax mirror. Additional patents were taken out in Czechoslovakia (1923), Austria, France, Germany, and Switzerland (1924). A US patent followed in 1926 The case of the original AVOmeter was a comb-jointed oak box with an ebonite lower front panel. The upper part of the front panel was cast aluminium. After around three years production, the volume of sales was sufficient to justify a redesign of the instrument, now with a movement whose full-scale current was 6 mA. The redesigned meter had 13 ranges and was constructed on a one piece phenolic moulding with the characteristic "kidney" shaped window. The back case was a deep drawn aluminium can on the back of which was a summary of the operating instructions, a feature of all future AVOmeters. The movement was originally protected by a short length of