Patent ID: 7596998

Claim:
A liquid level sensor, comprising: a ceramic substrate; at least two discrete thermistor/heater pairs attached to said substrate, each thermistor/heater pair arranged to be one above the other when said sensor is operably installed in a liquid container; at least one reference thermistor attached to said substrate and arranged to be below said thermistor/heater pairs when said sensor is operably installed in the liquid container, wherein said reference thermistor is attached to said substrate in a region lacking proximity to any heaters; one or more protective coatings applied to said substrate, wherein said protective coatings include a polymer layer applied over an inert glass layer; and a control module for receiving signals from the thermistors in order to determine at least whether the container is full or empty versus partially filled or partially empty; wherein heaters of said thermistor/heater pairs are electrically connected in parallel to form a parallel connection, and said parallel connection is connected in parallel with each thermistor of said thermistor/heater pairs and with said reference thermistor.