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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Thermocouple interface?
Date: Mon, 02 Dec 2002 05:10:35 GMT
NNTP-Posting-Date: Mon, 02 Dec 2002 00:10:35 EST
Richard Lamb wrote:
> There area all kinds of resistive sensors for automotive use.
> No problem reading those.
> But thermocouples are something else.
> Any experience or wild ideas?
The trick about thermocouples is that they really indicate the
difference temperature between the measurement couple and a reference
couple (usually assumed ot be at ice temperature). So any interface
not only has to deal with the low level (millivolt) signals, but has
to simulate the other couple at ice temperature to compensate for the
interconnection couples between the thermocouple metals and the
interface metals. This means the ice reference has to generate a
voltage that varies with the temperature of the interface amplifier.
There are specific analog chips that do all of this with very few
Some have A/D converters for digital output:
And some produce an analog output signal:
Or you can build up the whole thing with opamps and a precision
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