Re: Temperature probes (was Re: ATM Thermal behavior of mirrors)

[Anthony Stillman <atmer@flash.net>]

The LM335, available in a TO-92 package is a good choice for contact
temperature sensing. The LM335 is very linear with temperature having a
breakdown voltage proportional to 10mV per degree Kelvin.  It may be used
uncalibrated with a series resistor (~5K) and a high impedance volt meter.
The supply should be well regulated.  The reverse current should not exceed
15mA, but obviously you want to keep it as small as possible.  Basically,
think of this as a temperature variable zener diode.

To attach this transistor sized sensor to a substrate, I put a pin pricks
worth of heat sink compound between the flat side of the LM335 and the
substrate.  Then, careful to keep it in one place, smothered it with five
minute epoxy.  Oh yea, I solder wires to the leads and encapsulate them
with RTV first.

To characterize the sensors, never believe data sheets, I've used ice water
slush and boiling water straight out of the pan.  You can attach the
LM335's adjustment lead to the sweep arm of a 10K pot connected across (in
parallel with) the  devise to calibrate it.  But, as I've often been told,
why fix the hardware, it's a software problem.

Anthony