Position sensor

Abstract

We describe a position sensor comprising drive electronics to drive a first tuned resonant circuit at a resonant frequency, a moveable mechanical control associated with a second, passive tuned resonant circuit and read-out electronics coupled to the first tuned resonant circuit to sense a position of the control. A first frequency of resonance of the first tuned resonant circuit matches a second frequency of resonance of the second, passive tuned circuit, and the first and second frequency resonance match a resonant frequency of the drive signal. The first tuned resonant circuit has an input coupled to the drive electronics, an output coupled to the read-out electronics and a resonant LC circuit coupled in series between the input and output. The variable output signal is dependent on an amplitude of a signal at the output of the first tuned resonant circuit.

We claim: 
     
         1 . A position sensor comprising an active tuned resonant circuit, providing a signal which varies as the mutual separation of said active tuned resonant circuit and an electrically reactive element is varied, drive electronics connected to said active tuned resonant circuit and read-out electronics connected to either said active tuned resonant circuit or said electrically reactive element. 
     
     
         2 . A position sensor according to  claim 1  wherein the electrically reactive element housing comprises a second, passive tuned resonant circuit, and further comprising: drive electronics coupled to said tuned resonant circuit to drive said first tuned resonant circuit with a drive signal at a resonant frequency;
 read-out electronics coupled to said first tuned resonant circuit, to provide a variable output signal responsive to said relative position of said second, passive tuned resonant circuit with respect to first tuned resonant circuit, wherein a first frequency of resonance of said firsts tuned resonant circuit matches a second frequency of resonance of said second, passive tuned circuit, and wherein said first and second frequency resonance match said resonant frequency of said drive signal; 
 wherein said first tuned resonant circuit comprises an input coupled to said drive electronics, an output coupled to said read-out electronics and a resonant LC circuit coupled in series between said input and said output; and 
 wherein said position sensor is configured to provide a variable output signal is dependent on an amplitude of a signal at said output of said first tuned resonant circuit. 
 
     
     
         3 . A position sensor according to  claim 1  wherein the electrically reactive element comprises a passive tuned resonant circuit, or an electrically conductive object. 
     
     
         4 . A position sensor according to  claim 1 , wherein the mutual separation of the active tuned resonant circuit and the electrically reactive element is varied by a mechanism or housing which directs the relative movement between said active tuned resonant circuit and said electrically reactive element which allows the variation in said mutual separation to be linear, translational, angular or a combination of these. 
     
     
         5 . A position sensor according to  claim 4  wherein the mechanism or housing comprises a foot pedal, slider knob, or a rotary knob. 
     
     
         6 . A position sensor according to  claim 1 , wherein the mutual separation of the active tuned resonant circuit and the electrically reactive element is freely variable. 
     
     
         7 . A position sensor according to  claim 6  wherein the active tuned resonant circuit or the electrically reactive element is housed in a musical instrument or jewelry or clothing or baton or device moved by person or persons involved in a musical performance. 
     
     
         8 . A position sensor according to  claim 1  wherein the active tuned resonant circuit comprises an inductive coil, at least one capacitive element and a means of connecting the drive electronics. 
     
     
         9 . A position sensor according to  claim 8  wherein the active tuned resonant circuit further comprises an input resistor and at least two capacitive elements. 
     
     
         10 . A position sensor according to  claim 8  wherein the active tuned resonant circuit further comprises a means of connecting the read-out electronics to the inductive coil. 
     
     
         11 . A position sensor according to  claim 3  wherein the passive tuned resonant circuit comprises an inductive coil and a capacitive element. 
     
     
         12 . A position sensor according to  claim 11  wherein the passive tuned resonant circuit further comprises a means of connecting the read-out electronics. 
     
     
         13 . A position sensor according to  claim 8  wherein the inductive coils are formed from planar spiral tracks on a printed circuit board. 
     
     
         14 . A position sensor according to  claim 8  wherein the inductive coils are wirewound. 
     
     
         15 . A position sensor according to  claim 1  wherein the read-out electronics comprise a synchronous demodulation circuit, or a non-synchronous demodulation circuit, or a phase-sensitive rectification circuit or a phase-insensitive rectification circuit. 
     
     
         16 . A position sensor according to  claim 3  wherein the active tuned resonant circuit and the passive tuned resonant circuit are tuned to have the same frequency of resonance. 
     
     
         17 . A position sensor according to  claim 1 , wherein said sensor is usable as an electronic circuit element to directly control a musical effect signal. 
     
     
         18 . A position sensor according to  claim 1 , wherein the output from said sensor can be used to control a separate circuit element in an musical effect electronic circuit or converted to a digital value via an analogue-to-digital-converter and used as an input parameter to a digital signal processing algorithm or transmitted as musical instrument digital interface (MIDI) messages. 
     
     
         19 . A position sensor according to  claim 16  wherein a plurality of position sensors are operated in close proximity where each position sensor operates at a different frequency of resonance. 
     
     
         20 . A position sensor according to  claim 16  wherein a plurality of position sensors are operated in close proximity where each position sensor operates at the same frequency of resonance.