Capacitance measuring device for measuring a distance for a working head of a laser processing system, where the capacitance between a nozzle electrode and a conductive workpiece surface serves as a measured variable

摘要

#CMT# #/CMT# The capacitance measuring device for measuring the distance for a working head of a laser processing system, is claimed, where the capacitance between a nozzle electrode (2) and a conductive workpiece surface (1) serves as a measured variable. The capacitance together with the inductance of a coil (5) of resonant circuit components form a high frequency oscillator (6), which provides a frequency-dependent capacitance of the measuring signal. The nozzle electrode is completely or partially surrounded by a shield electrode (14). #CMT# : #/CMT# The capacitance measuring device for measuring the distance for a working head of a laser processing system, is claimed, where the capacitance between a nozzle electrode (2) and a conductive workpiece surface (1) serves as a measured variable. The capacitance together with the inductance of a coil (5) of resonant circuit components form a high frequency oscillator (6), which provides a frequency-dependent capacitance of the measuring signal. The nozzle electrode is completely or partially surrounded by a shield electrode (14). A shield driver amplifier of the shield electrode provides magnitude and phase of same high-frequency potential as that of the nozzle electrode, where an amplitude limit ensures that the shield driver amplifier remains in the linear working range. The resonant circuit is a series resonant circuit or a parallel resonant circuit. The shield electrode completely or partially shields the nozzle electrode against the nozzle body. The high frequency oscillator, the shield driver amplifier, the amplitude limiting function, the coil and other components of the resonant circuit are completely or partially integrated into a housing closer to the working head and in the nozzle body of the working head. The amplitude limiting function is wholly or partly integrated in the oscillator circuit. The frequency jump at the contact between the nozzle electrode and the workpiece is evaluated as error signal. #CMT#USE : #/CMT# The capacitance measuring device is useful for measuring a distance for a working head of a laser processing system. #CMT#ADVANTAGE : #/CMT# The capacitance measuring device ensures simple, accurate and efficient measurement of the distance for the working head against troubles by smoke, metal vapor, splashes and plasma with reduced measuring spots and side sensitivity. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The figure shows a schematic view of a capacitance measuring device. 1 : Conductive workpiece surface 2 : Nozzle electrode 5 : Coil 6 : High frequency oscillator 14 : Shield electrode.