Patent attributes
An absolute electromagnetic position encoder comprises a readhead and an absolute scale. The readhead comprises field generation and detection configuration and a readhead processor. The absolute scale comprises an active periodic signal pattern, an active absolute signal pattern, and timing and activation circuitry connected to the active signal pattern. During an energy transfer cycle, the timing and activation circuitry is configured to receive and store energy from the readhead. During a first signal generating cycle, the timing and activation circuitry is configured to drive the periodic spatially modulated signal generating element in order to generate first cycle spatially periodic signals in the first cycle field detector. During a second signal generating cycle, the timing and activation circuitry is configured to drive the first spatially modulated signal generating element in order to provide at least one corresponding second cycle signal in the readhead. The readhead processor is configured to determine an absolute position of the readhead relative to the absolute scale based on at least the second cycle signal and the first cycle spatially periodic signals.
