Dealing with thermocouples - and building thermocoupls

[C. Brooks]

How about uploading it to the FTP site for future reference? Could use a
descriptive name like "tc_amp" or some such...

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


----- Original Message -----
From: Rich M <rsrich at cwcom.net>
To: <diy_efi at diy-efi.org>
Sent: Friday, June 16, 2000 5:33 PM
Subject: RE: Dealing with thermocouples - and building thermocoupls


> I've used a simple circuit to very good effect using the LM35 as a cold
> junction compensator and a single good quality op-amp (Linear Technology
> LTC1050) and a handful of passives to provide the gain.
> One important consideration if you are doing your own op-amp circuit is to
> ensure you use a good op-amp with very low input offset voltage (Vios)
> specification. Consider that a 'K' type thermocouple generates a voltage
to
> the tune of 40 microvolts per degree centigrade, an input offset voltage
> value which is significant with respect to this level can produce a
> measureable error. The LTC1050 has a value of a handful of microvolts but
> doesn't cost a packet (approx. 2.5UKP in small quantities). Anyone
> interested is  welcome to a .pdf of the schematic if it's helpful.
> As a side benefit, this circuit behaves predictably if the thermocouple
> becomes disconnected; not designed that way, just happened!
>
> Rich


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