klm 366 - "lenses"

[The Old Crow]

On Fri, 4 Feb 2000, [iso-8859-1] Dr. Jörg Schmitz wrote:

> but another question : I also found (on the top left corner
> of the voice board) 3 resistors with the caption "TH1", "TH2",
> "TH3". They are black and look like lenses. I supposed, that
> these are tempcos, and tried them out. They all have 100 Ohm,
> and, surprisingly, with cooling down, the resistance INCREASED.
> The tempcos I know behave reverse, i.e. increasing resistance 
> by warming up.

  They're thermistors.  Typically used for temperature sensing and
compensation; their behavior is as you observed: resistance *decreases*
with increasing temperature.

  Very popular for junction-compensation of thermocouples in process
control industry.

  --Crow

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