Patent ID: 6298709
Filing Date: 2001-10-09
Classification: G01D,G01P

Abstract:
A device for determining a time-dependent measured variable within a useful band of the time-dependent measured variable, the device comprising:a measurement circuit including a measuring element and an analysis arrangement, the measuring element supplying a measurement signal, the analysis arrangement obtaining an output voltage from the measurement signal, the output voltage representing the time-dependent measured variable, the measurement signal being present at an output of the device; anda self-test module for superimposing a test signal with a test frequency above the useful band on the time-dependent measured variable, the test signal being superimposed concurrently with the determination of the time-dependent measured variable, the self-test module including a frequency-selective detection device, a voltage-force converter, and an interrupt logic circuit, the frequency-selective detection device picking off a reaction of the measurement circuit to the test signal at the output, the voltage-force converter being capable of activation via an output of the frequency-selective detection device so that a signal for compensating the test signal may be superimposed on the time-dependent measured variable, the interrupt logic circuit being capable of activation from the output of the frequency-selective detection device with a window comparator, the interrupt logic circuit detecting whether the reaction of the measurement circuit is outside of a value range, the interrupt logic circuit assigning a fixed voltage level to the output of the measurement circuit when the reaction of the measurement circuit is outside of the value range.