System for sensing the position of a movable electrical contact
A position sensor assembly includes: a first elongated electrical conductor, a second elongated electrical conductor, extending substantially in parallel with the first elongated electrical conductor, and a movable electrically conductive contact component, configured to move along lengths of the first elongated electrical conductor and the second elongated electrical conductor, simultaneously contacting both of the first elongated electrical conductor and the second elongated electrical conductor at different positions along each of their lengths. In such an assembly, the first elongated electrical conductor and the second elongated electrical conductor typically have a combined resistance of less than 1 ohm per meter. In any event, such an assembly can be used in a signal-reflection-based position-sensing system.
1 . A system for sensing position, comprising:
a movable contact assembly that includes
a first elongated electrical conductor,
a second elongated electrical conductor, extending substantially in parallel with the first elongated electrical conductor, and
a movable electrically conductive contact component, configured to move along lengths of the first elongated electrical conductor and the second elongated electrical conductor, simultaneously contacting both of the first elongated electrical conductor and the second elongated electrical conductor at different positions along each of their lengths;
a signal generator having an output coupled so as to provide a time-varying periodic signal to an input end of the first elongated electrical conductor;
a signal-timing comparator having: a first input coupled to the output of the signal generator, a second input coupled so as to receive a reflected signal from the input end of the first elongated electrical conductor, and an output providing a signal indicative of a timing difference between signals at the first input and the second input of said signal-timing comparator, thereby also being indicative of a current position of the movable electrically conductive contact component.
2 . A system according to claim 1 , wherein the time-varying periodic signal is a sinusoid.
3 . A system according to claim 2 , wherein the signal-timing comparator comprises an analog phase discriminator.
4 . A system according to claim 1 , wherein the signal-timing comparator comprises a signal multiplier that multiplies a signal provided to the first elongated electrical conductor and the reflected signal.
5 . A system according to claim 1 , wherein the time-varying periodic signal has a frequency of at least 1 Megahertz (MHz).
6 . A system according to claim 5 , wherein the frequency of the time-varying periodic signal is at least 10 MHz.
7 . A system according to claim 1 , wherein the second elongated electrical conductor surrounds the first elongated electrical conductor.
8 . A system according to claim 7 , wherein the first elongated electrical conductor is coaxial with the second elongated electrical conductor.
9 . A system according to claim 1 , wherein the movable electrically conductive contact component is part of a larger movable contact assembly that also includes an elongated member that slides along at least one of the first elongated electrical conductor or the second elongated electrical conductor.
10 . A system according to claim 9 , wherein the elongated member is tubular and has a length of at least 50% of the length of the first elongated electrical conductor.
11 . A system according to claim 10 , wherein the elongated member surrounds the first elongated electrical conductor.
12 . A system according to claim 9 , wherein the larger movable contact assembly is mechanically coupled to a piston that is driven within a cylinder, thereby causing the movable electrically conductive contact component to slide along the first and second elongated electrical conductors when the piston is driven.
13 . A system according to claim 1 , wherein the output of the signal generator is coupled to the input end of the first elongated electrical conductor through a forward path of a directional coupler, and the input end of the first elongated electrical conductor is coupled to the second input of the signal-timing comparator through a reverse path of the directional coupler.
14 . A system according to claim 1 , wherein the first input of the signal-timing comparator is coupled to the output of the signal generator through a second forward path of the directional coupler.
15 . A system according to claim 1 , wherein the movable electrically conductive contact component contacts at least one of the first elongated electrical conductor or the second elongated electrical conductor via a plurality of contact elements that are separated from each other.
16 . A system according to claim 15 , wherein said contact elements are made of a spring-like material.
17 . A system according to claim 1 , wherein the first elongated electrical conductor and the second elongated electrical conductor have a combined resistance of less than 1 ohm per meter.