ABSOLUTE ENCODER SCALE CONFIGURATION WITH UNIQUE CODED IMPEDANCE MODULATIONS

摘要

An absolute scale configuration is provided for use in a position encoder which includes a readhead and a scale. The absolute scale configuration includes a plurality of scale loops distributed along a measuring axis to provide a position dependent signal that varies depending on a relative position between the scale loops and the readhead. At least some of the scale loops are coupled to respective impedance modulating circuits connected to receive energy from current induced in the scale loop and to provide a unique coded modulation of the scale loop impedance during a code signal generating state. The unique coded modulations as sensed by the readhead are indicative of a coarse resolution absolute position, which may be utilized in combination with the position dependent signal to determine an absolute position with a high resolution.