Method for determining at least one physical parameter using a sensor unit

Abstract

In a method for determining at least one physical parameter, a sensor unit which is activated by at least one periodic excitation () is provided, wherein the sensor unit has at least one detection region in which changes of the parameter in the surroundings of the sensor unit lead to output signal () from the sensor unit. The sensor unit is wired such that if there are no changes of the parameter in the detection region the output signal () is a zero signal or virtually a zero signal at the output of the sensor unit, whereas if there are changes of the parameter in the detection region the output signal () is a signal that is not zero and has a specific amplitude and phase. In a closed control loop, the non-zero signal in the receive path is adjusted to zero using a control signal to achieve an adjusted state even in the presence of changes of the parameter in the detection region. The control signal is evaluated in order to determine the physical parameter. The output signal () from the sensor unit is reduced substantially to the fundamental wave of the excitation () and the output signal () is controlled to zero in the entire phase space by means of at least one pulse width modulation. A temperature-stable, fully digital measuring system is provided as a result of the fact that the at least one pulse width modulation itself generates a correction signal with a variable pulse width and possibly a variable phase which is then added to the output signal () from the sensor unit and the output signal is thereby controlled to zero in the entire phase space, wherein the pulse width of the correction signal and/or the phase of the correction signal is/are determined by the deviations of the output signal () from zero.