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A new thick film material system produces smooth long wearing conductor patterns surrounded by a non-abrasive insulating surface. The insulator/conductor interface is essentially co-planar which allows extremely long life with a sliding contact. Mechanical, electrical and environmental integrity are excellent due to use of high temperature cermet materials on the alumina ceramic substrates. Manufacturing costs are low due to the process simplicity. Several automotive electronic components utilizing this technology are described.

Fluid level sensors for fuel and other liquids have been designed using two resistor technologies. One method provides a sensor with a variable resistance 2 wire signal in the 0 to 500 ohm range for use with most conventional magnetic gauges. Another method provides a Potentiometric 3 wire signal for use with electronic gauges. Both resistor technologies are suitable for fuel level sensors in trucks, off-road vehicles, and storage tanks. Descriptions of several recent applications are discussed.

For many years, fluid level measurement in fuel tanks has been accomplished using a float and lever arm to operate a variable resistor. The resistance reading is translated by any of several gauge designs. The float and lever arm sensor requires a significant amount of tank space and has accuracy and reliability problems. A new family of linear sensors utilizing various thick film materials is discussed. The devices utilize conductive plastic or cermet resistors on various substrates and may be operated as a 2-wire variable resistor or 3-wire potentiometer. Significantly less space is required and the shape of the signal output curve can be adjusted to fit a variety of tank designs. The linear sensors are adaptable to the modular reservoir fuel delivery systems now in use.

Variable resistor/potentiometric position sensors have been used in automotive applications for many years. Significant improvements in reliability and quality have resulted in their being designed into many new control systems. The history of these devices, design considerations, testing procedures, and future trends are discussed.