At 11:44 AM 8/14/02 -0700, you wrote:


>Could always just go with a Fluke type-K thermocouple immersion
>probe.  Produces a milivolt/degree C or degree F output.  Scale it
>with an opamp, and read with a PIC.  Not too tough.  Little bit pricy
>though.  I think it would cost about $300USD for the set.  Though if
>you're looking at TIG welding, it could also get that high,
>considering the rates for professional welding...

Probe would be about $75. with a platinum sensor. Signal conditioner
could get it up to the $200 range or higher depending on accuracy
(but they are not that hard to make if you don't need isolation
or industrial-strength EMI immunity). Signal level with RTDs is
about 10* that of a thermocouple.

Thermocouples are not appropriate for that temperature range and
application, the  cold junction compensation contribution will be
as much as the thermocouple, you may as well dump the thermocouple
and stick the compensator down the tube.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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