Dealing with thermocouples - and building thermocoupls

[C. Brooks]

Hi Roger, National has an IC "LM335" (Which is actually a temp sensor in and
of itself) which can be used for cold junction compensation. Application
Note 225 on the National site explains in detail how to go about
accomplishing that. You can take the output signal from any of the circuits
provided in the appnote and run it through an opamp to bring it up to
whatever voltage your ADC requires.

For signal conditioning on a budget, I HIGHLY recommend the "Active Filter
Cookbook", "The IC OP-AMP cookbook", and a book titled (I believe) "The
hobbyists guide to the 555".

Between op-amps and 555 timers there isn't much you won't be able to
accomplish as far as signal conditioning goes.

Thermocouples are so inexpensive that  wouldn't bother trying to make my
own. I've had custom thermocouples made by Gulf Sensor for past projects.
You can find them at http://www.gulfsensors.com/

I prefer the "Assembly Style 1A" sensor with the miniature connector "SM2"
and using an extension cable made with a male TC connector on one end and a
female on the other and whatever length of TC wire I need. It makes for a
cleaner setup and easy replacement of TC's if they fail.

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: Friday, June 16, 2000 1:03 PM
Subject: Re: Dealing with thermocouples - and building thermocoupls


>
>
> I found (on digi-key) a chip that is a Thermocouple cold junction
> compensator and matched amplifier, it will supposely work for all
> types of thermocouples and coverts to 10mv/dC.
>
> Does anyone know how hard it is to build a thermocouple from parts?
> Omega seems to have everything needed to build one including
> everything to contain the probe.
>
> Roger


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