Dealing with thermocouples - and building thermocoupls

[Rich M]

Thanks very much Peter for uploading that for me, anyone interested in a
simple (cheap) thermocouple amplifier with cold junction compensation, take
a look. Hope it helps.
Rich.

> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Peter Gargano
> Sent: 19 June 2000 11:36
> To: rsrich at cwcom.net
> Cc: diy_efi at diy-efi.org
> Subject: Re: Dealing with thermocouples - and building thermocoupls
>
>
> Hi Rich (cc: DIY),
>
> Your circuit is on /incoming (it's 10,363 bytes dated Jun 19 03:20)
>
>   ftp://ftp.diy-efi.org/incoming/thermocouple_amp.pdf
>
> Rich M wrote:
> >
> > 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!
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