System for evaluating AC sensor signal carried on large DC signal

摘要

The evaluation system has conversion electronics, which are designed for detecting a sensor voltage signal (US) and producing a digital control signal as a function of the information signal amplitude (USAC). The electronics include a comparator (12), for comparing the sensor voltage signal with a reference signal (UR). The system also has a voltage generator (20), which provides a controlled output of a voltage signal (UG) at a discrete level and is connected to a charge storage device (22,24) that has a first time constant for producing the reference signal. A control unit (28) is provided to control the voltage generator, and is designed in such a way, that this switches cyclically between two voltage steps with a short repeat frequency, as compared to the first time constant. The system also has an evaluation unit (16), for the pulsed detection of a number of comparator output signals, and especially their keying ratio. The control unit produces a digital control signal.