> Anyone here ever measure very low temperatures (-100=BAC) by measur=
ing
Vforward for a given Iforward?
There are several high dollar diodes out there (GaAlAs, GaAs, and Si)=
 that
are extremely well characterized and thus good for the task, but I'm =
trying
to stay on the cheap here.

Does anyone have any data about Vforward vs Temp for a common (i.e. c=
heap)
Si diode at very low temperatures?
>

If you don't mind a slightly more complex method (ie OK if you are us=
ing a
processor for measurement control and can accept a 2 step current sou=
rce)
you can use a method that depends ONLY on diode material and doesn't =
need
calibrating when you change diodes. Sounds good :-).

This method uses the CHANGE in forward voltage drop per current when =
you
change currents between two known values.
ie You measure the diode voltage drop at two preset current values an=
d the
difference in voltage drops is proportional to diode temperature as d=
evice
specific constant values cancel out. You get the same result for all =
diodes
of the same type eg Silicon.
Regrettably a quick Google did not produce any references. Someone he=
re
should be able to comment.

FWIW: Excellent overview article on temperature measurement technique=
s. (Not
directly related to the query but useful background).

    http://www.sensorsmag.com/articles/0900/17/main.shtml




        RM

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