| 摘要 |
The simplified signal-processing circuit arrangement for processing and evaluating signals indicative of the status of an FSR-foil pressure sensor utilized in a seat-occupancy detection device, makes use of the fact that an application-oriented, integrated circuit, present in a motor vehicle having digital open-loop and closed-loop control functions implemented in a microcontroller MCU, contains a highly precise, switchable test-voltage source. One end of a circuit containing the FSR-foil is connected to a switching output VTA of the ASIC carrying the highly precise test voltage. The other end of this circuit is connected to a port of the MCU. A measuring voltage, which is a function of the status-contingent current intensity through the FSR-foil, drops off across a reference resistor connected in series to the FSR-foil, is fed to an analog-digital converter input of the MCU, and is converted therein into a digital signal indicating the occupancy status of the FSR-foil. Thus, using only one precise, switchable, d.c. voltage source, one port of the MCU and one ADC port, it is possible to evaluate the OCCUPIED/NOT OCCUPIED status of the FSR-foil, as well as to detect various fault conditions. |
