| 摘要 |
An encoder for detecting the angular position of a shaft of an electric motor comprises an encoder disc (101) having tracks (515) sensed by detectors in reading heads (106a, 106b). Analog position signals from the detectors are sampled in sampling circuits (1701-1704) at times given by sampling pulses issued by a device such as a counter (506). The sampled analog values are converted to digital values by a converter (1706) and provided to a local processor (1707) calculating position values. The local processor sends commands to the device (506) to issue sampling pulses at accurately defined times, normally regularly spaced in time. The local processor also receives, from a central processor, read command signals commanding to it provide position values. These read command signals normally arrive rather regularly but are not synchronised. In order to provide positions values at suitable times after receiving the read command signals, the local processor can send its commands earlier or later, in relation to the normal regular rate.
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