Re the use of transistors as temperature sensors, am I right that they offer a more-linear response than a simple diode?
I built a thermometer using a simple diode (silicon signal) many years ago, and that has linearity adequate for my purposes over 0-100'C when calibrated. The advantage it may offer over a transistor is that you can configure it so that one lead projects forward and is then folded back again, thus forming a very compact 'sensing pad'.
I used it recently on a flanged resistor, together with K-type thermocouple sensor right along side. During fast heating, the diode was really fast to respond, always showing an appreciably higher reading than the thermocouple. During slow cooling, the two probes gave the same reading.
S