Hi all, We are using a diode connected transistor (TIP32C) as a temperature sensor. 77K to 400K. We bought a whole bunch with the same production code. I measured the room temperature forward voltage drop and then selected three transistors. Two outliers and one in the middle. I then measured the forward voltage drop vs. temperature. Data shown here,
And then took the difference between the middle one and the outliers. Data shown here,
It's nice and linear. Especially for those with larger forward voltage drops than average. I can do a room temperature, single point calibration of the diodes and get better than 0.1 degree K accuracy over most of the range. I thought some of you might be interested.
Oh, On the second graph I put in some other diodes as a quick test. room temp, 150K and 77K.
George H.