At 05:29 PM 06/03/1997 -0500, you wrote:
>Analog Devices used to make a chip like that. I think it was an AD590. It
>did cold junction compensation and gave a linear voltage output for the
>temperature.
>

Sorry no.  AD590 is an expensive but fairly accurate temeprature sensing
device that outputs 10 uA per degree Kelvin.

A thermocouple needs Cold Junction Compensation and linearization in order
to properly function.  ie:  The thermocouple wire is brought to a connector
block that that has a temperature sensor connected to it (like an AD590).
Then the voltage is measured and put into a polynomial to determine the
actual temperature measured at the other end of the thermocouple wire.

Easiest way to do the CJ compensation is to use the LT1025 from Linear
Technologies.  Set a jumper for whcih type of thermocouple you are using and
make it physically close to your terminal block and Voila` It gives you the
value you need for K or J or T type thermocouples.  For a really good
description on how to use thermoouples get an OMEGA catalog.  It's the
definitive description and has all the tables you need.

Regards,

John
Pioneers are the ones, face down in the mud,
with arrows in their backs.
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