Patent ID: 7714586

Claim:
A control unit for sensing an oil level of an engine of a motor vehicle, comprising: a voltage source having an output outputting an output voltage; a sensor resistor having a value being dependent on its temperature, wherein said sensor resistor senses the oil level of the engine of the motor vehicle substantially independently of an initial temperature of said sensor resistor; and a reference resistor connected in series with said sensor resistor, the output voltage of said voltage source dropping across said sensor resistor and said reference resistor in a connected state, said reference resistor being dimensioned such that a power loss of said sensor resistor is substantially constant for a range of resistance values of said sensor resistor; and an evaluation unit generating a control signal and connected to said control unit, said evaluation unit having a regulator, said regulator controlling a regulated variable being a voltage drop over said sensor resistor and said reference resistor, and outputting an actuating signal, said actuating signal being the control signal.