Can you send the circuit (ASCII art) or put it on a website somewhere. It
sounds a bit as if the input resistances to the opamp + and - terminals are
different and a change in bias current with temperature is giving you an
offset. - Otherwise the input offset voltage may be changing with
temperature and you may need to go to a better opamp or provide external
compensation. (I don't know the specs of the CA3130 opamp sorry)

And are you sure that it's not the air heating inside the (sealed ?)
submarine that not giving you the pressure offset?

Richard P




In a message dated 23/09/2002 15:06:57 GMT Daylight Time,
Steve.Goring@BSKYB.COM writes:


> I have a problem - I am taking the differential o/p of a wheatstone
bridge
> measuring
> pressure to a ca3130 op amp.
>
> I have managed to scale it nicely from .02v to 4.8v for i/p to a Pic A/D
-
> however
> when the op amp changes temperature the o/p changes dramatically !!!
>

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