The Wave technology  probe consists a thin layer of thermocouple  for liquids temperature measurement

The junction of dissimilar metals produces electric potential related to emperature.

The MAX thermocouple is standardized against a reference temperature of 0 degrees Celsius by the use of  Thermistor

Max Engineering has developed a method of monitoring ( measuring)

continuous and discrete liquid level  with a temperature profile of a heater. By heating the connecting wire and monitoring at each point on the probe's  heater, the velocity of the increasing temperature is monitored. The difference between one point and the point where a largest  temperature increase jump occurred , will indicate fluid level.