Re: Avometer Movements
Sinewave,
As you state, the basic sensitivity of the Model 40 movement is 3mA. I'm sure you know the sensitivity of these movements is set by means of the magnetic shunt, but for the benefit of anyone finding this thread in future, I'll describe these.
For horseshoe magnets the magnetic shunt is in the form of two flat steel strips clamped to the narrow sides of the magnet by a single long screw. (1st Attachment)
For block magnet movements, the magnetic shunt is as shown in the second photograph, actually of a Model 8 X, but the construction is the same.
If the movement sensitivity cannot be brought to the correct value by the magnetic shunt, the magnet should ideally be remagnetised and "artificially aged". The process saturates the magnet then reduces the flux to give the required sensitivity. There are probably still meter repairers with the necessary equipment but finding them may not be easy.
Some people have reported some success by using small auxiliary disc magnets attached to the main magnet, but there is a risk that the field between the pole shoes may be uneven which could affect the scaleshape (linearity) of the movement.
PMM
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