DEVICE FOR SENSING PRESENCE OF AN ELECTRICALLY CONDUCTING OBJECT

摘要

Device for detecting the presence of an electrically conducting object (1) in a predetermined area. There is a device (23) for emitting a driving signal in the shape of an alternating current. There is also a capacitive sensor element (5) and a means (30) to detect the change in capacitance between said sensor element and the surroundings which is caused by present object or absent object. A second capacitive element is formed by a second sensor element (29) which is driven by a second driving signal (25) which is in counter-phase relative to the first driving signal (24). Alternatively, the second capacitive element can be in the shape of a screening element which load-wise is isolated from the sensor element but maintains essentially the same potential as it.