>KISS
>Why not use a single supply Op-Amp that goes rail to rail (LMC6462
>comes to mind)? Use the + input to bias the output to + full scale
>for temp of 0 in (zero adj), and just invert the A/D conversion in
>software.
>Then you don't need a -5V supply.

>Thomas McGahee wrote:
>>
>> Personally, I would use the AD590 to provide current to an op-amp
>> "current to voltage converter". Scaling is a function of the feedback
>> resistor. For example, you are interested in a range from 0 to 100
degrees
>> centigrade. That is a *change* of 100 degrees Kelvin, which would be
>> a change of 100 ua. Let's say you want to scale this to produce
>> an output that varies from 0-2.50 volts in 1000 steps: you would
>> get .1 degree for each .025 volts. (recall that you get 2048 counts for
>> a 0-5.12 volt input assuming your reference is 5.12 v)

The kiss idea is what I am trying to do. By using a 10K resistor in the
bottom leg of the AD590 you get the current to voltage conversion done nice
and easily in a manner that should feed the A/D in the pic OK. Worst case I
will need a single voltage follower op-amp after a MUX (I will have between
8 and 16 sensors). It converts the 1uA/K to 10mV/K and I am then hoping to
introduce the offsets by setting the Vref+ and Vref- to appropriate values.
As Vref+ to Vref- needs to be 2V min, it looks like I will need to be
setting my values from -50C to +150C, and possibly doing a single constant
subtraction to get it all within an easily convertible range.

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