Dealing with thermocouples - and building thermocoupls

[C. Brooks]

Hi Roger, the wire run should have only two dissimilar metal junctions  (One
for each lead). The junctions should be physically close to each other to
maintain an equal temperature for each junction. The reason for the equal
temp  is to negate any voltage bias caused by the junctions (Which act like
TC's themselves). In essence, you have three TC's total only one of which,
you are interested in.

In addition to this, the dissimilar metal junctions and the IC doing the CJC
need to be as close as possible for the same reason as above. Any
temperature difference between the junctions, or between the junctions and
the CJC will induce errors in the final output.

Oh yeah Orin about the AD597's....   THANK YOU!! I've been looking for a
single chip solution to thermocouple signal conditioning ever since the
first project!

Charles Brooks
Mid-Atlantic Speed Shop
http://www.massmotorsports.com


----- Original Message -----
From: Roger Heflin <rah at horizon.hit.net>
To: <diy_efi at diy-efi.org>
Sent: Tuesday, June 20, 2000 10:00 AM
Subject: RE: Dealing with thermocouples - and building thermocoupls


> On terminating thermocouples:
> Where the plug is put, the thermocouple is terminated?  And at this
> point you can run normal wire to the computer setup?
>
> I am still trying to understand exactly how these devices work and
> exactly what I need.
>
> I have decided to use a 80C52-basic processor.  It has external
> address lines and can be programmed in basic or assembler and has
> built in a serial interface to get into the chip.   It should be fast
> enough for what I need and I will be playing some addressing tricks to
> allow me to have quite a bit more ram than the 64k it can address
> without tricks.
>
> Roger
>
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