Dealing with thermocouples - and building thermocoupls

[Roger Heflin]

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

 On Fri, 16 Jun 2000, Bernd Felsche wrote:

> Jörgen Karlsson tapped away at the keyboard with:
> 
> > Does anyone know of a adc that can use an external reference with very low
> > voltage, I have found units that can be used with a 1V reference but I would
> > like to get down to 50-60mV. I am trying to limit the part count needed for
> > type K thermocouples.
> 
> The Atmel 8-bit AVR RISC MPUs allow Aref as low as Agnd. Something
> like an AT90S8535 has 8 analog channels and dozens of digital I/O to
> drive displays, etc as well as heaps of other functions. Chip cost
> is fairly low; you should be able to source one-offs at about US$20.
> 
> 	http://www.atmel.com
> 
> It's fairly straight-forward to record values in the limited on-chip
> RAM, or to hook up an external data-logger (PC or palmtop) via RS232
> (UART on-chip), or the SPI. The ADC is a 10-bit process. The part is
> typically rated at -40C to +85C.
> 
> There are smaller AVR processors with fewer I/O which might be
> sufficient.
> 
> -- 
> Bernd Felsche - Innovative Reckoning
> Perth, Western Australia
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