if we want to be ultra precise, often the probe does not actually contain a thermometer. most often they use a device that will change its electric resistance with temperature. the electronics then measure that value, and do a calculation to arrive at the temperature. and according to wikipedia, there are 3 common classes of such devices, each with different subtypes and designs and different prices and temperature ranges and different degrees of precision. thermistors, silicon bandgap temperature sensors and resistance temperature detectors .
maybe, if the whole thermostat is quite inexpensive, buying a new one really isnt a bad idea. i would first ask hydrofarm directly.
Well since the unit I'm talking about is sold as a "thermoMETER", I'll leave it at that. Why complicate things for no reason?