[Amps] Calibrate a panel meter?

[Dr. David Kirkby]

Bill Turner wrote:
> I have a Simpson 923A panel meter, 1 amp full scale. It is reading 
> low by about 6%. When it has 800 ma through it, it indicates about 
> 750 ma. I'll be using it in my 8877 amp at 800 ma and I'd like it to 
> be more accurate.
> 
> If it were reading high, I could just shunt it, but reading low...???
> 
> Is there a way to calibrate it by adjusting anything inside? Moving 
> the magnets around, etc? I'm sure the factory calibrates them somehow 
> but I've never read anything in the ham literature about how to do it.
> 
> Suggestions appreciated.
> 
> 73, Bill W6WRT

I'm not aware of being able to calibrate them, but if you don't mind 
making your own scale, you can avoid that. With a graphics package you 
can add your own scales, but green, yellow and red areas for good, 
warning, danger etc. Personalise it somewhat. Solves the problem and 
makes it look better too.

I wonder if it has been repaired and a few turns removed from the moving 
coil? If it is not a moving coil.