Abstract: A readhead is provided for reading an absolute scale, optionally a passive magnetic scale, that encodes a series of data bits. The readhead includes a plurality of sensors, such as an array of Hall sensors, for producing a plurality of sensor signals. A plurality of signal combiners are also provided to receive at least two of the sensor signals and produce therefrom a combined sensor signal. A plurality of data bit extractors are arranged to receive at least two combined sensor signals and to determine the value of a data bit encoded in an associated absolute scale. The readhead also comprises an incremental signal generator for generating at least one incremental signal from the combined sensor signals produced by a plurality of the signal combiners. In this manner, both absolute and incremental position is measured.

Abstract: The present invention relates to an encoder readhead. The readhead includes a housing having an opening for capturing an encoder scale including an elongate rod having a substantially circular cross-section, the opening defining an axial direction along which a captured encoder scale can slide back and forth. A scale reader, which may include an array of Hall sensors, is provided for reading a portion of an encoder scale located in the opening. The housing includes an access portion that allows the encoder scale to be inserted into, and/or removed from, the opening by a relative movement between the housing and the encoder scale in a direction other than the axial direction.

Abstract: A magnetic encoder apparatus is presented that includes a plurality of magnetic sensor elements (e.g. Hall sensors) for reading an associated magnetic scale that produces a periodically repeating magnetic pattern. The plurality of magnetic sensor elements produce a plurality of sensor signals and an analyzer is provided for analyzing the plurality of sensor signals to provide a measure of the position of the magnetic sensor elements relative to the associated magnetic scale. The analyzer is arranged to use the plurality of sensor signals to assess the period of the periodically repeating magnetic pattern sensed by the plurality of magnetic sensor elements. In this manner, the requirement to carefully match the period of the sensor elements with the periodically repeating magnetic pattern of the associated magnetic scale is avoided.

Abstract: The present invention relates to an encoder readhead. The readhead includes a housing having an opening for capturing an encoder scale including an elongate rod having a substantially circular cross-section, the opening defining an axial direction along which a captured encoder scale can slide back and forth. A scale reader, which may include an array of Hall sensors, is provided for reading a portion of an encoder scale located in the opening. The housing includes an access portion that allows the encoder scale to be inserted into, and/or removed from, the opening by a relative movement between the housing and the encoder scale in a direction other than the axial direction.

Abstract: A readhead is provided for reading an absolute scale, optionally a passive magnetic scale, that encodes a series of data bits. The readhead includes a plurality of sensors, such as an array of Hall sensors, for producing a plurality of sensor signals. A plurality of signal combiners are also provided to receive at least two of the sensor signals and produce therefrom a combined sensor signal. A plurality of data bit extractors are arranged to receive at least two combined sensor signals and to determine the value of a data bit encoded in an associated absolute scale. The readhead also comprises an incremental signal generator for generating at least one incremental signal from the combined sensor signals produced by a plurality of the signal combiners. In this manner, both absolute and incremental position is measured.