Rolfe, Edward William

An inductive encoder comprising first and second members relatively moveable along a measurement direction, configured such that: the first member has, arranged at or toward a front side thereof which faces the second member, at least a first scale track; and such that the second member has, arranged at or toward a front side thereof which faces the first member: an excitation coil through which an alternating current is passed at a predetermined operating frequency so as to generate an alternating magnetic field which is manipulated by the first scale track; and at least a first receiver coil for sensing the alternating magnetic field as manipulated by the first scale track, via which the relative position of the first and second members along the measurement direction can be measured. The inductive encoder is further configured such that: i) the first member comprises magnetically permeable material having a relative magnetic permeability µr of at least 2 at said operating frequency so as to increase, at least at the first scale track, the magnetic flux density of the magnetic field generated by the excitation coil; and/or ii) the second member comprises magnetically permeable material having a relative magnetic permeability µr of at least 2 at said operating frequency so as to increase, at least at the first scale track, the magnetic flux density of the magnetic field generated by the excitation coil.

A method of demodulating an amplitude-modulated signal, which is the result of a baseband signal that has been amplitude-modulated onto a carrier signal having a carrier frequency, the method comprising: a) sampling the amplitude-modulated signal so as to obtain a series of sampled points comprising: i) a plurality of temporally-distinct sampled points each of which is obtained at a first phase with respect to the period of an unmodulated version of the carrier signal; and ii) a plurality of temporally-distinct sampled points each of which is obtained at a second phase with respect to the period of an unmodulated version of the carrier signal; b) using the sampled points of i) and ii) to form a reconstructed baseband signal.

A rotary scale apparatus for an encoder apparatus comprising a planar disc on which at least one track comprising scale features is provided, in which the planar disc comprises a hole through its centre for receiving a cylindrical shaft, and in which the rotary scale member comprises at least three cantilevered spring members which are provided substantially in plane with the planar disc and spaced around the edge of the hole, for engaging with, and radially locating the disc on, a cylindrical shaft inserted therethrough.

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A head unit via which a device can be mounted onto a positioning apparatus, the head unit comprising: a first mount provided at a first end of the head unit, for mounting a device thereon; a second mount provided at a second end of the head unit, for mounting the head unit on a positioning apparatus; a first set of electrical contacts for electrically connecting to a device mounted on the first mount, the signals from which are passed through to a first plug or socket electrical connector on the head unit, the first plug or socket electrical connector comprising a set of electrical contacts and a mechanical interface for fitting with a counterpart plug or socket electrical connector on the positioning apparatus; and a second set electrical contacts, different to and separate from the first set of electrical contacts, for electrically connecting to a device mounted on the first mount, the signals from which are passed through to a second plug or socket electrical connector on the head unit which is different to and separate from the first plug or socket electrical connector on the head unit, the second plug or socket electrical connector comprising a set of electrical contacts and a mechanical interface for fitting with a counterpart plug or socket electrical connector on the positioning apparatus.

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