Re: Avometer Model 40 Special (7.5mA FSD)
Dave,
From the interior photographs, there are a number of things about your meter which look unusual to me.
The first is the multiplier wound on the glass former; this looks to be longer and of a smaller diameter than in most Model 40s. From memory, it's also considerably later in date than mother Model 40s which used this type of multiplier - most seem to be from the early 1940s. The wire used in those I've seen is very thin, less than 50 swg, which could be whu they're so fragile and seldom seen in useable condition today.
Then, all the other shunts and multipliers a slab wound resistance elements. By 1947, most Avometers were using component resistors for several multipliers. Could the use of slab wound multipliers have been for better temperature stability or higher accuracy, or both?
The cut away apertures in the case would suggest that the meter had been incorporated in some control or monitoring desk or along with other instruments in a test set or jig of some kind.
PMM
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