can still be found in regular use. The earlier versions of models 7, 8 and 9 had a design flaw which resulted in many instruments sustaining damage to the movement in transit. Users would habitually 'switch off' the instrument by setting the AC switch to 'DC' and the DC switch to 'AC'. With the switches at these settings, the movement is completely undamped. The operating manuals for the affected instruments did contain a note that they should not be switched to 'AC' and 'DC' (or the blank position either side of the 'AC' and 'DC') though failed to explain why. The problem was solved on later instruments by providing the DC switch with an 'OFF' position (see illustration above). Present times Despite continuing demand from customers, production was stopped in 2008, reportedly due to increasing problems with suppliers of mechanical parts. The last meter to leave the factory was an AVOmeter Eight Mk 7 (Serial Number 6110-610/081208/5166) which was presented in February 2010 to the winner of a competition run by the Megger company. Principal models General purpose multimeters "The AVOmeter" - 1923 to 1928 7 ranges direct current, direct voltage and resistance (DC) AVOmeter - 1928 to 1939, Originally 13 ranges, later extended to 22 ranges through use of "divide by two" push button switch Universal AVOmeter - 1931 to 1939, originally 20 ranges, later extended 34 and 36 ranges through use of "divide by two" push button switch, replaced by Model 40 Universal AVOmeter Model 40 1939 to c. 1986. A development of the 36-range Universal AVOmeter incorporating automatic cut-out and internal construction similar to the Model 7 (Basic ranges to 12 A and 1200 V, the former extendable with accessory current shunts). 167 ohms/volt. "High Sensitivity" meters principally for Radio and Electronics Universal AVOmeter 50-range Later known as Model 7 (1936 to c. 1986): A "High Sensitivity" multimeter for radio servicing. (Basic ranges to 10 A and 1000 V, the former extendable with accessory current shunts. A power factor and wattage unit was also available). 500 ohms/volt with divide by two button in normal position, 1000 ohms per volt with divide by two button pressed. AVOmeter model 8: May 1951 to November 2008 (7 'Marks') (Basic ranges to 10 A and 1000, 2500 or 3000 V depending on Mk.). 20,000 ohms/volt DC, 1000 ohms/volt AC. AVOmeter model 9: Essentially similar to model 8 but with international symbols