At present electronic theodolite has been used widely in Angle measuring, according to the Angle measuring principle can be divided into incremental counting method and absolute coding method.
电子经纬仪是目前应用较为广泛的角度测量仪器，按其角度测量原理可分为增量计数法和绝对编码法。
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There summarize the operating principle of absolute, incremental and hybrid encoder, introduce the choice principle of optical-encoder model and the measuringmethod of rotor speed and rotor position.