Device for the contactless detection of the distance between two objects, in particular the safety distance between a person and moving machine parts

摘要

In a device for the contactless detection of the distance between two objects, the input of an evaluation unit, which operates in a frequency-selective and phase-selective fashion, is connected to a receiving electrode (7) which is surrounded by an insulator and to which there are assigned field-generating first and second transmitting electrodes (5, 6) to which antiphase ac voltages are applied via first and second drive amplifiers (10, 11). The amplitude ratios of the ac voltages are adjusted with the aid of a zero-point correction circuit (24, 21) in such a way that the currents influenced in the receiving electrode (7) by the transmitting electrodes (5, 6) cancel one another out. According to the invention, the first and second transmitting electrodes (5, 6) as well as the receiving electrode (7) are arranged in a screening housing (3) in which an opening (8) is provided through which one external receiving electrode (57) projects. The object (2) to be detected is connected via a switch (13) to the voltage of one of the drive amplifiers (11). <IMAGE>