Serial number 0506 M90258
Digital battery powered AVOmeter made by Thorn EMI Instruments in Dover, England in March 1986. The multimeter has a clear digital readout on a 45mm X 10mm LCD screen. It will measure AC and DC voltage and current as well as resistance and continuity. Range adjustment is accomplished via two slide switches. The instrument is protected by two fuses (2A and 10A) and powered by a 9 Volt PP3 size battery.
This is a view of the inside, the two printed circuit boards are connected together via two multi pin connectors and the range change switches form part of the left hand circuit board which is attached to the front panel.
This was given to me by Rupert Russell who said it was bought by Cosworth engineering in 1986 to aid servicing the Sierra's but it drove them a bit mad when some internal fuse blew and it had to go back to the maker to mend, twice, as the 1st time the repair failed! The other thing about it that was kind of disappointing was the max volts being 200, so it was unable to record mains volts..! But as home race car diagnostic tool it had been great and reliable, until he tried to calibrate a displacement sensor recently, and the correlation between the 20 and 2 range was too great to inspire confidence, so has been superseded by something from Maplins.
We have not been able to find any information about this instrument, so perhaps it only had a short production run? Do you know anything about the DA 2003? Some digital meters were made by Gossen Metrawatt and re-badged for AVO, though in this case the circuit boards and the casing indicate manufacture in Dover.