Re: AVO Model 7 Restoration
Ian,
Temperature compensation was advertised as one of the characteristics of the Model 7 in the advertisements which announced its introduction so it seems certain that it was used from the beginning until the movement design changed.
It was patented, GB 476682, application date 12th May 1936, Complete Specification accepted 13th December 1937. The Model 7 was introduced in August 1936.
The complete specification states:
"The chief object of the invention is to provide means for compensating for changes in ambient temperature and to provide some correction for overheating due to misuse of the meter, whereby the accuracy of the reading may be retained within the limits of temperature compensation possible with the device".
I have never seen another Avo instrument which uses this form of compensator. This could be because the Model 7 was the most sensitive "full-size" Avometer until the Model HR was introduced around 1948, but the HR had a block magnet movement which perhaps did not need temperature compensation. The first HR which I obtained did however have temperature compensation using a thermistor. It had been fitted with a Model 8 Mk III movement in what seemed to have been a factory repair.
PMM
|