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An incremental encoder employs a quadrature encoder to generate its A and B output signals. The pulses emitted from the A and B outputs are quadrature-encoded, meaning that when the incremental encoder is moving at a constant velocity, the A and B waveforms are square waves and there is a 90 degree phase difference between A and B .
A linear encoder is a sensor, transducer or readhead paired with a scale that encodes position. The sensor reads the scale in order to convert the encoded position into an analog or digital signal, which can then be decoded into position by a digital readout (DRO) or motion controller. The encoder can be either incremental or absolute.
A rotary incremental encoder has two output signals, A and B, which issue a periodic digital waveform in quadrature when the encoder shaft rotates. This is similar to sine encoders, which output sinusoidal waveforms in quadrature (i.e., sine and cosine), [ 13 ] thus combining the characteristics of an encoder and a resolver .
The interface keeps track of position by counting encoder pulses. It counts up when the quadrature phase difference is positive and down when the difference is negative, or vice versa. To do this, interfaces employ a quadrature decoder to convert the A and B pulses into direction and count enable signals, which in turn control an up/down counter.
The quality the codec can achieve is heavily based on the compression format the codec uses. A codec is not a format, and there may be multiple codecs that implement the same compression specification – for example, MPEG-1 codecs typically do not achieve quality/size ratio comparable to codecs that implement the more modern H.264 specification.
So for applications where 8 tracks were too bulky, people used single-track incremental encoders (quadrature encoders) or 2-track "quadrature encoder + reference notch" encoders. Norman B. Spedding, however, registered a patent in 1994 with several examples showing that it was possible. [74]
Incremental encoding is widely used in information retrieval to compress the lexicons used in search indexes; these list all the words found in all the documents and a pointer for each one to a list of locations. Typically, it compresses these indexes by about 40%.
An encoder is a sensor which turns a position into an electronic signal. There are two forms: Absolute encoders give an absolute position value. Incremental encoders count movement rather than position. With detection of a datum position and the use of a counter, an absolute position may be derived.