I need an inexpensive instrument to measure cryogenic temperatures (down to -200C).
I can build a thermistor-based thermometer using an Arduino that is accurate to under 1 degree for 0 to 100C.
First of all, can ordinary NTC thermistors be used at cryogenic temperatures? Second, if I were to try to use this approach, I would need ways to calibrate the device.
I have found a chipset from Analog Devices that would let me use a thermocouple down to that range.
I would take other ideas on how to build one, but then I need some equipment to calibrate whatever I build. Is there anything I can buy for < $100, I don't need huge accuracy, but I need something.