Abstract: In a sensor circuit arrangement, a capacitance of a sensor capacitor is measured by a circuit which supplies a corresponding sensor signal. The circuit comprises a differential amplifier with an input, an output and a feedback loop between the input and the output. It further comprises a first capacitor arranged in the feedback loop, and a switching arrangement for charging the sensor capacitor from a voltage source in a first phase and for transferring a charge from the sensor capacitor to the integrating capacitor in a second phase. The circuit further comprises a second capacitor arranged in parallel to the first capacitor in the second phase for limiting a gain of noise generated by the differential amplifier. The sensor circuit arrangement further includes a low pass filter for filtering the sensor signal.

Abstract: A thermal flow sensor is equipped with a self-test unit that monitors the device and generates a fault signal in the presence of a malfunction. The self-test unit can e.g. monitor the integrity of a membrane carrying the heater and temperature sensors, or it can monitor various operational parameters of the device, thereby increasing the safety of the device.

Abstract: The invention relates to a method for recognizing identification media in the communication area of a write/read device functioning according to the principle of inductive coupling in the MHz range, wherein an antenna is used for transmitting and receiving HF signals, in addition to a circuit for transmitting HF signals with a standard transmitter power output and a logic circuit for evaluating communication between a write/read device and an identification medium. A short inquiry signal consisting of several fundamental components of the HF field and having a standard transmission power output is periodically transmitted via a transmission path and the antenna and a response signal is detected on the antenna. The response signal is compared to a reference signal and a communication signal is transmitted in order to recognize an identification medium in the event that the response signal is different from the reference signal.