VULCAN20 wrote:
> The sensor may be located as far as 100 FT away. and temprange of  32
> deg to200 deg F( approx 0C to 100C)
>
> What I am looking for from the group is this:
> Does anyone have Hands on  experience with temperature control
> sensors and could recomend a better temperatur sensor.  We would like
> to imerse it in the water.

Whatever sensor you use, I think you should convert to digital close to the
sensor, then send only digital information over the 100ft link.  This can
include checksums so that the receiver knows when something gets corrupted.
Even something like a 10F222 might be good enough, but a little bigger PIC
with 10 bit A/D and UART will be easier.  The current demands should be so
low that you could send 10V or so, linearly regulate that down to 5V at the
sensor, then send back a digital data stream.  If you're worried about
noise, send the data back differentially.  Since temperature changes slowly,
you can use a very slow baud rate and still have it be instantaneous from
the application point of view.  That would require a total of 4 wires:
Power, ground, and 2 differential data lines.


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