Re: Op-Amp ----- any experts around this afternoon?

["Nick" <nick@xxxxxxxxxxxxxxx>]

> just a  correction. There is no need
> for the diode as the ouput is in
> Kelvin. Subtract 2.73 from the reading
> and you get Celsius. Sorry for that.
>
> /Ake

Ake, I must be getting there because I was just about to ask why I
needed the diode!  You beat me to it with your second post.

Thanks for the link.  That shows three resistors which if I am
calculating correctly, should be:

Rf = 20k
Rin = 2.2k

to get the gain of ten (Equally I guess I could use 200k and 22k,
and I'm not sure how to choose).  Then:

Rz = 0.5k

as it suggests a value "equal to the parallel combination of Rf and
Rin" which, if I remember rightly is the sum of the reciprocals.

How am I doing so far?  If I am understanding ok so far, then I
think I have the gain aspect sorted, giving me 1 volt per 10 degrees.

I am not sure how to achieve the "offset" so that the 0-5v values
that Comfort expects are at a sensible place within the device's
spectrum.  In other words, what I have so far, I think, will still
give 0v at 0 degrees kelvin and 5v at +50 degrees Kelvin.

What I need is 0v at -10 degrees Centigrade and 5v at +40 degrees
Centigrade.

Hope that makes sense.  Thanks again,

Nick

PS, once I get this sorted, I'll publish the results as it sounds
like a very cheap way of getting temperatures into Comfort (etc).