An Advanced Electrothermal Sensor for Automotive Level Measurement

This paper describes a fuel level sensor, which basically consists of thin-film resistors encapsulated in Kapton foils. The thin-film elements are heated by constant current pulses and the immersed part is cooled by the liquid to be measured. This results in a change in resistance which can be detected by various types of evaluation circuitry discussed in the paper. This electrothermal principle has a number of advantages compared to conventional methods:

• - long life due to absence of mechanical moving parts or contacts
• - high media compatibility including ethanol or methanol containing fuels
• - high resolution in the “empty region”
• - easy shaping of output characteristics with unusual tank shapes

A status report on development progress is given including test results with first prototypes and a discussion of the achieved error-band.