Hi Bill,
I believe that meter is in the 50 mV family -- You can confirm this
supposition by measuring the voltage drop at 1A (full scale). The intrinsic
movement is likely 5mA.
Inside the meter, you should encounter a small series R, slightly less than
ten ohms, connected from one end of the shunt to the coil. Shunt this R with
something around 100 ohms (perhaps, a 200 ohm trimpot?) and you should be able
to bring the meter back into calibration.
73 & Good evening,
Marv WC6W
-- Bill Turner <dezrat1242@ispwest.com> 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
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