Re: Online guide for hobby-level DIY thermocouples?

On Sun, 02 Dec 2007 22:14:19 GMT, the renowned _
<jtayNOSPAMlor@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sun, 02 Dec 2007 17:04:18 -0500, Spehro Pefhany wrote:

On Sun, 02 Dec 2007 19:54:55 GMT, the renowned _
<jtayNOSPAMlor@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

I think I'd like to experiment measuring temperature with some small
electrical meters - freezing to boiling or a bit higher. Pointers to
useful info on the web sought - thanks...

That's not a great range in which to be using a thermocouple. Did you
have some specific reason to want to use a T/C?


No - just thought that for an analogue meter a device that made
(milli)volts all by itself would be likely to keep things simple. What's
better?

A thermistor or semiconductor sensor would be simpler to work with.
National, for example, has some. Thermistors are nonlinear so a bit
harder to work with, but cheaper and more accurate in quantity (not
necessarily more stable). A coil of copper wire can be a cheap
temperature sensor. A loose coil of thin Pt wire is one of the most
stable temperature sensors made. If you are not so fussy, a thin film
of the stuff will do. HVAC folks use thin films of base metal stuff
like nickel.

Here's a semiconductor sensor that costs around $1 in small
quantities: http://cache.national.com/ds/LM/LM94022.pdf

You need a sensor such as the above in order to be able to use a
thermocouple anyway! (for cold junction compensation).


Best regards,
Spehro Pefhany
--
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