AD590 Temperature Sensor
We use the
Analog Devices AD590
temperature sensor to measure
the temperature of three items in the Dewar.
These sensors have a linear current
versus absolute temperature in the
range of -55 to + 150 C.
In the past we had found them to usable
to about 60K even though it was well
below the manufacturer's recommendation.
However, the more recent batch seemed to have
a non-monotonic temperature coefficient below
about about 130 K.
I have traced this to a failure of the
constant current behavior as a function
of drain voltage.
I believe that operating the AD590 at a
minimum voltage to get you up on the flat
portion of the curve will still give a
somewhat reliable (or at least monotonic)
temperature reading.
Below is a sequence of curves of an AD590
in series with a 10k resistor.
The ordinate is the voltage across the
resistor; the abscissa is the total voltage
across the resistor and the AD590.
Each curve was taken during the cooldown
of a sensor on the 20K stage.
Last Revised April 26, 1999