> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of Philip Stortz
> Sent: Sunday, October 17, 2004 3:05 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE]: Temperature sensor for my oven?
>
>
> i've seen lower prices for the very basic bare junction type for
> multimeters.  also check omega.com, lots of thermocouples and wire (and
> you can make your' own thermocouple from the wire by welding it together
> with a capacitor discharge, ideally but not necessarily in argon
> depending on your accuracy needs, or even soldering though it's not
> ideal).  for a single device, ebay is of course often helpful.  the nice

Yes, Omega has lots of stuff. Good tutorial section on thermocouples in
their catalog too.

When desperate I have in a pinch twisted the thermocouple wires together
tightly using a bench vise and pliers - no welding or soldering. I've never
checked to see how *Bad* this is. I know it's not ideal, but when you don't
have anything else it's better than nothing.

> thing about thermocouples is that they are nearly linear, an rtd is a
> terribly non-linear thing.  then again thermocouples have their down
> side as well, but i like them for reasonably high temperatures.  an rtd
> (or thermistor) is best for control around a single point, then you can
> set up a bridge etc. with the appropriate value resistors, otherwise you
> need that pesky lookup table which adds code and makes a pure analog
> solution difficult.  i believe national and/or ti also have chips
> specifically for interfacing with thermocouples.

FWIW, Linear Technology makes thermocouple interface chips too (We use the
LTKA00 & LT1025 chipset for J type applications)

-Mark




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