Sensor device and method for operating a sensor device

#Priority is claimed to European Patent Application No. EP 19157089.4, filed on Feb. 14, 2019, the entire disclosure of which is hereby incorporated by reference herein.

#The present invention relates to a sensor device for measuring variable physical quantities and to a method for operating such a sensor device.

#In order to measure variable physical quantities, such as temperature and humidity, there are known sensor devices which output the respective measured quantities via a signal-processing unit as pulse-width modulated (PWM) signals after suitable preprocessing and further processing. The measured quantity is contained in the generated PWM signal and encoded therein by way of the duty cycle p of the PWM signal. The duty cycle p is understood to be the ratio of the duration tH of a HIGH level to the signal period duration tP=tH+tL in the rectangular PWM signal; i.e., p=tH/tP, with tL denoting the duration of a LOW level in the PWM signal. For further processing of the PWM signal, the PWM signal having the measured-quantity-dependent duty cycle p is typically demodulated and amplified by an amplifier unit and thus converted into an analog current or voltage signal within a certain current or voltage range. For example, in the case of a current signal, a current range between 4 mA and 20 mA, and, in the case of a voltage signal, a voltage range between 0 V and 10 V are typical ranges for the analog output signal. However, in practice, the electronic components used both in the signal-processing unit and in the amplifier unit are subject to variations, which may result, for example, in varying voltages of the PWM signal, varying offset voltages of operational amplifiers or varying resistance tolerances of amplifier stages. The result is that even if the quantities measured are identical, the measurement values output by the sensor device in the form of the analog current or voltage signals vary unacceptably from sensor device to sensor device, thus impairing the desired measurement accuracy.

#Embodiments of the present invention will be described in even greater detail below based on the exemplary figures. The present invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the present invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:

#FIG. 1 is a highly schematic block diagram of a first exemplary embodiment of the sensor device according to the present invention;

#FIG. 2a is a schematic detail view showing a portion of the block diagram of FIG. 1 to illustrate the conversion of a PWM signal into an analog voltage signal;

#In an embodiment, the present invention provides a sensor device for measuring variable physical quantities that enables analog current or voltage signals relating to the measured physical quantities to be output with high accuracy and reliability and with the least possible circuit complexity.

#In another embodiment, the present invention provides a method for operating a sensor device for measuring variable physical quantities that enables analog current or voltage signals relating to the measured physical quantities to be output with high accuracy and reliability.

#The sensor device according to an embodiment of the present invention includes: at least one sensor which measures variable physical quantities and provides a raw sensor signal at its output, a digital signal-processing unit for preprocessing the raw sensor signal provided by the sensor into a sensor signal, the signal-processing unit further processing the sensor signal thereby converting it into a pulse-width-modulated output signal whose duty cycle is dependent on the measured quantity, for which purpose a plurality of device-specific correction parameters are stored in a memory unit, which are used by the signal-processing unit to convert the sensor signal into the pulse-width modulated output signal, and an amplifier unit which converts the pulse-width modulated output signal into an analog voltage or current signal.