Capacitive device for the measurement of displacements

摘要

The device comprises a scale (1) and a slide (2) which are provided with electrodes arranged to form two pairs of capacitances for the measurement of the displacement of the slide on the scale (CA1-CA2, CB1-CB2). These measurement capacitances are connected to an electronic feed and processing circuit (3) in which they are connected in a bridge (4A, 4B) with switched reference capacitances of MOS type. In this circuit, the outputs of these bridges are connected via comparators (5A, 5B) to a processor (6) of CMOS type adapted to produce a terminal digital measurement signal by counting the periods of the signal of the measurement capacitances and by numerical interpolation within each of these periods. This interpolation is effected by balancing the capacitive bridges by means of a digital algorithm.