Apparatus for converting measurement signals into digital signals, the signals having been initiated in a piezo sensor by the impacts of a hydraulic percussion device

An apparatus for converting measurement signals into digital signals suitable for processing in a microprocessor ( 12 ), with the signals having been initiated in a piezo sensor ( 6 ) by accelerations acting on the sensor during the impacts of a percussion device ( 1 ), particularly a hydraulic hammer, and being used to determine the number of work strokes that have been executed in the impact direction (arrow 3 ) of the percussion device ( 1 ). The conversion apparatus includes: a rectifier ( 8 ) that is connected to the output ( 6 a ) of the piezo sensor ( 6 ) and suppresses the negative component of the measurement signal; a peak-value detector ( 9 ) that is connected to the rectifier ( 8 ) and converts the remaining, positive component of the measurement signal into an envelope curve; a high-pass filter ( 10 ) that causes the envelope curves of consecutive measurement signals to be converted into intermediate signals whose amplitude respectively has a zero passage; and a comparator ( 11 ) that is disposed downstream of the high-pass filter ( 10 ) and whose output is connected to the digital input ( 12 a ) of the microprocessor ( 12 ), thereby effecting the conversion of the intermediate signals into digital signals having a rectangular amplitude response.