[sdiy] Thermistors and Keys

[René Schmitz]

Hi David and all!

>Another couple of beginner questions.
>
>First, I've been looking at a schematic that uses thermistors. Are
>thermistors and tempo resistors the same thing, or something completely
>different?

What we refer to as thermistors is usually a negative temperature
coefficient (NTC) resistor, these are made out of semiconductor materials
like Si. 
The tempco resistors have a positive temperature coefficient, these are
simply 
platinum resistors. Metals have increasing resistance with temperature,
whereas semiconductors have decreasing resistance with temperature.

If the resistor in question is in the lower leg of a voltage divider, or
the feedback resistor of an opamp, its most likely a platinum resistor. If
its in the upper leg, with another resistor in series, its a NTC.

There is some also information on this topic at my website.

I have to leave the keyboard question to someone else.

Cheers and a Happy New Year,
 René



-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159