1. Field of the Invention
The present invention relates to a sensor module for detecting an operating parameter of a motor vehicle.
2. Description of the Related Art
It is known to use sensor modules of many different types, in particular in motor vehicles, to acquire various operating parameters, such as pressure sensors, position sensors, air mass sensors, distance sensors, brightness sensors, and the like. The sensor modules convert the physical quantity that is to be acquired, i.e. the relevant operating parameter, into an electrical signal that is supplied to a central or remote data processing device for further processing.
In particular, active sensor modules are used that require a power supply, for example in order to acquire the operating parameter or in order to prepare a sensor signal directly at the sensor module in order to enable disturbance-free transmission. In motor vehicles, the supply voltage required for this is transmitted via a supply line that can have a high resistance, for example due to corroded or incompletely joined plug contacts. If, however, an active sensor module is supplied with a voltage that is too low, the signals emitted by the sensor module are faulty or unreliable.
Sensor models are known that recognize undervoltage and overvoltage states of the voltage supply. If the supply voltage falls below or exceeds a fixed, specified voltage threshold, this state is recognized by the sensor module. The sensor module then interrupts the transmission of the sensor signals to the data processing device. Alternatively, the sensor module can send an error signal (instead of the measurement signal). The decision as to whether an undervoltage or overvoltage is present takes place in the sensor module, due to the specified thresholds, and requires a significant circuit outlay. An example of such a sensor module is given in the following.
Published German patent application document DE 41 05 283 A1 describes a flow measurement device having a pressure sensor connected to a computing unit. In addition, an undervoltage recognition circuit is connected to this computing unit. If a voltage collapse is detected, the computing unit locally stores all important data. Accordingly, the supply voltage is immediately evaluated locally and protective measures are taken directly at the location in the sensor module. This requires complex circuit parts in the sensor module for the evaluation of the supply voltage and for the taking of the protective measures. In addition, in the sensor module elements must be provided that enable a secure storing. This requires a high-capacitance energy storage device that ensures the supply of energy during the data storing.
The complex circuit elements for the voltage evaluation and for the data storage, and of the energy storage device, require complex circuit elements and produce a significant space requirement. Because in particular in automotive technology little space is available for sensors, and the additional circuit elements cause a substantial circuit outlay, an object of the present invention is to reduce the space requirement in comparison with the existing art and to reliably recognize a drop in voltage in a sensor module.