Aaron wrote...

>Basically, I need to interface a couple of sensors to a PIC with A/D. The
>PIC and A/D side I can take care of, but these sensors are setup such that
>they are a variable resistance to ground. For example, one of them is an
>automotive pressure sensor with a 10-187 ohm resistance to ground, and I
>would like to convert that to a variable voltage. Oh, and most of the
>sensors are linear.
>
>I was thinking about trying to use the sensor as part of a voltage divider
>and 2 op amps to offset and amplify the voltage to a 0-5V range, then I
>could simply handle the unit conversion in software. This would be the
>correct way to do it, right?

Yes, that's probably the easiest way to do it--though you could
get by with only one opamp per channel, arranged as a
non-inverting amplifier referenced to ground, if you're willing
to put up with an output range slightly narrower than 0-5V.

>I was trying to find a simpler way of interfacing these sensors because I
>will have several of them, each with different resistance ranges, so trying
>to setup and calibrate the resistance values for each one seems like a big
>pain.
>
>Should I just shut up and start trying to setup the op amps for each of
>these sensors, or is there an easier way? Maybe someway to utilize the fact
>that they are resistance to ground?
>
>Any help or pointers to information is greatly appreciated.

I think you're going about it the right way; I can't think of any
other approach that would be much simpler.

HTH...

Dave

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