Fraunhofer-gesellschaft Zur Foerderung Der Angewandten Forschung E.v.

Stefan Moedl

Josef Sauerer

Johann Hauer

Norbert Weber

Marcus Hartmann

A capacity measuring circuit includes a measuring voltage source configured to feed a sinusoidal voltage signal to a first terminal of a capacity to be measured so as to cause a temporal change in a charge stored on the capacity to be measured. The capacity measuring circuit additionally includes a delta-sigma modulator. The delta-sigma modulator is configured to receive a charge from a second terminal of the capacity to be measured and to provide a digital output signal which is dependent on a quantity of the charge received from the capacity to be measured. The capacity measuring circuit may be employed in a sensor system.

Capacity measuring circuit, sensor system and method for measuring a capacity using a sinusoidal voltage signal

The present invention is based on the finding that a capacitance can be measured precisely and efficiently when, in a delta-sigma modulator having an operational amplifier, a first capacitor connectable to an input of the operational amplifier, and a second capacitor in a feedback branch of the operational amplifier, a reference signal source is connectable to the first capacitor, wherein the first or second capacitor may represent a capacitance to be measured. Due to the fact that, in contrast to what is conventional, no input quantity is measured and digitalized at the input of the delta-sigma modulator, but instead a defined reference signal source is coupled at the input and a device of the delta-sigma modulator itself represents the measuring quantity, an extremely compact circuit is provided allowing capacitances to be measured quickly and reliably, the measuring result being additionally made available in a digital form.

Capacitance measuring circuit

A device for non-contractual measurement of the speed of an object moving over a surface comprises a means for radiating a signal of fixed frequency at an angle onto the surface in or against the direction of motion, said angle being variable by the movement of the object, and for receiving a Doppler-shifted signal reflected at the surface. A means is provided for combining a plurality of reflected Doppler-shifted signals, which are received in temporal succession, so as to produce a combined spectrum. The device for non-contractual speed measurement additionally comprises a means for detecting from the combined spectrum the spectral portion having the highest or lowest frequency and exceeding a predetermined signal power, and a means for deducing the speed from the frequency of the detected spectral portion.

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Hilpolstein, Germany

Stefan Moedl