Rotary encoder especially for application in measurement instrument, such as theodolites, has binary coding circuit for coding two sinusoidal signals, and control unit with processor

摘要

The encoder includes binary coding circuit (72,72b), voltage detector (73), and control unit (75) with processor, which calculates from input voltage an average value for each of two sinusoidal signals. The processor interpolates the calculation with the input voltage and the average value in order to calculate a rotational angle of interpolation of the step rotary encoder. A turnable part features a magnetic sensor (54), which outputs two sinusoidal signals with a phase difference of 180 degrees, and a difference amplifier (71,71b) for intensifying the difference of the two sinusoidal signals. A non-volatile memory (76) reads-out a previously stored average value for interpolation calculation, and a closed loop control compares the average value with predetermined target voltage in order to approximate the mean of the target voltage, by adjusting offset voltage of difference amplifier. The mean voltage is used for processing phase difference signals.