Peter L. Peres wrote:
>
> > One really cheap method is to use a 5w resistor,
> > the white ceramic wire-wound type.
>
> Hm. there usually have 300 to 500ppm/deg temperature coefficient. This is
> not so good. But there is an even cheaper method I've used (and still
> use).  Use a tiny signal lamp rated maybe 30mA and 24V. This is around 800
> Ohms when lit. When cold it is typically 1/2 to 1/10 of that. Use as a
> RTD. It is good to almost 700C when the glass softens. I usually hold them
> above a mild gas flame in tweezers until the bulb is drawn by the vacuum
> and contacts the filament (on all sides). This reduces the time constant.
> Use twiddled or compression connections or point weld. Solder won't work!


Cool! An excellent idea, and with the interesting
"glass-blower" approach is very interesting. So you
modify the bulb to become a special purpose temp
sensor?
Does it matter if the bulb vacuum fails?

The larger resistance (10k+) wire wound resistors
use a very fine nichrome wire and over 100'C
they are quite usable for temp trip points and
some low res temp measuring.
:o)
-Roman

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