PULSED WAVEGUIDE SENSING DEVICE AND METHOD FOR MEASURING A PARAMETER

• US 20100327880A1
• Filed: 03/26/2010
• Published: 12/30/2010
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: OrthoSensor, Inc (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Stein, Marc
• Granted Patent: US 8,427,176 B2
• Time in Patent Office: Days
• US Class Current: 324/639
• CPC Class Codes: G01D 5/48 using wave or particle radiation means G01D5/26 takes precedence
• CPC Class Codes: G01L 1/165 with acoustic surface waves
• CPC Class Codes: G01L 1/255 using acoustic waves, or acoustic emission G01L1/10 and G01L1/16 take precedence
• CPC Class Codes: G01L 5/167 using piezoelectric means
• CPC Class Codes: G01L 5/173 using acoustic means

Abstract

At least one embodiment is directed to a sensor for measuring a parameter. A signal path of the system comprises an amplifier (612), a sensor element, and an amplifier (620). The sensor element comprises a transducer (4), a waveguide (5), and a transducer (30). A parameter such as force or pressure applied to the sensor element can change the length of waveguide (5). A pulsed energy wave is emitted by the transducer (4) into the waveguide (5) at a first location. The transducer (30) is responsive pulsed energy waves at a second location of the waveguide (5). The transit time of each pulsed energy wave is measured. The transit time corresponds to the pressure or force applied to the sensor element.

Claims

1. A low power measurement system for measuring a parameter comprising:

a medium where the parameter to be measured affects the medium;

a first transducer coupled to the medium at a first location where the first transducer emits a pulsed energy wave into the medium in response to a pulse;

a second transducer coupled to the medium at a second location where the pulsed energy wave propagates through the medium to the second location and where second transducer generates a signal in response to the pulsed energy wave; and

a pulsed system including;

an edge detect circuit for detecting an edge of the signal from the second transducer; and

a first pulse circuit for generating a pulse to initiate a subsequent measurement sequence in response to a detected edge by the edge detect circuit where a transit time of the pulsed energy wave propagating from the first location to the second location is measured and the transit time or change in transit time corresponds to the parameter.

2. The system of claim 1 where a sensor form factor comprises a stack of the first transducer coupled to a first surface of a waveguide and the second transducer coupled to the second surface of the waveguide.

3. The system of claim 1 further including an amplifier having an input coupled to an output of the pulse circuit and an output coupled to the first transducer.

4. The system of claim 3 where the amplifier includes circuitry to dampen a wave shape for optimal transmission and reception in accordance with a matched network.

5. The system of claim 1 where the pulsed energy wave is a damped ringing waveform and where the edge detect circuit detects a leading edge of the signal from the second transducer and where upon detecting the leading edge of the signal, the edge detect circuit is disabled from edge detecting for a predetermined period of time.

6. The system of claim 5 where the transit time corresponds a time measured from the pulse provided to the first transducer to the detected edge of the signal from the second transducer.

7. The system of claim 6 further including a second pulse circuit for providing one or more pulses to the first transducer to initiate a sensing process where the second pulse circuit is decoupled from the first transducer when the edge detect circuit detects an edge of the first pulsed energy wave corresponding to the one or more pulses provided by the second pulse circuit.

8. The system of claim 7 where the first pulse circuit is coupled to the first transducer to provide the pulse to initiate the next measurement sequence when the second pulse circuit is decoupled from the first transducer.

9. The system of claim 8 where the pulsed system modulates a time period of pulsed energy waves as a function of changes in distance or velocity through the medium of the one or more pulsed energy wave propagating structures, or a combination of changes in distance and velocity, caused by changes in the one or more pulsed energy wave propagating structures.

10. The system of claim 9, further comprising a digital block for digitizing the frequency of operation of the pulsed system where the frequency corresponds to a time period of one or more pulsed energy waves.

11. The system of claim 1 where the pulsed system is configured to operate wireless according to one or more operational criteria, such as, but not limited to, power level, applied force level, standby mode, application context, temperature, or other parameter level.

12. The system of claim 1, where the system operates to measure changes in transit time due to changes in the length of the medium such that the physical length change under load are in proportion to the applied force.

13. A low power method of measuring a parameter comprising the steps of:

emitting a pulsed energy wave into a medium at a first location where the medium is subject to the parameter being measured and where the pulsed energy wave is generated in response to a pulse;

receiving a propagated pulsed energy wave at a second location in the medium;

generating a signal corresponding to the propagated pulsed energy wave;

detecting an edge of the signal where a transit time of the propagated pulsed energy wave from the first location to the second location is measured and the transit time or change in transit time corresponds to the parameter;

emitting a pulsed energy wave into the medium at the first location for a subsequent measurement in response to a pulse provided when the edge of the signal is detected.

14. The method of claim 13 further including a step of initiating sensing by emitting one or more pulsed energy waves into the medium in response to one or more pulses.

15. The method of claim 14 further including a step of maintaining an integer number of pulsed energy waves propagating in the medium where each pulsed energy wave has a time period and where the time periods of pulsed energy waves changes in response to changes in the parameter applied to the medium.

16. The method of claim 14 further including the steps of:

measuring the transit time or time period of each pulsed energy wave; and

converting the transit time or time period to the parameter being measured.

17. A method of measuring a parameter comprising the steps of:

maintaining more than one discontinuous pulsed energy waves in a medium subjected to the parameter being measured;

measuring the transit time of the pulsed energy wave through the medium; and

relating the transit time and material properties of the medium to the parameter being measured.

18. The method of claim 17 further including a step of maintaining a fixed integer number of pulsed energy waves in the medium during measurement of the parameter.

19. The method of claim 17 further including:

emitting pulsed energy waves into a first location of the medium; and

detecting pulsed energy waves at a second location of the medium.

20. The method of claim 19 further including a step of initiating measurement by providing at least the fixed integer number of pulses to a first transducer responsive for emitting pulsed energy waves into the medium.

21. The method of claim 20 further including the steps of:

generating a pulse from a signal provided by a second transducer responsive to pulsed energy waves at the second location; and

coupling the pulse to the first transducer where the first transducer emits a pulsed energy wave into the medium in response to the pulse.

22. The method of claim 21 further including the steps of:

shaping the pulse generated from the signal provided by the second transducer; and

impedance matching for efficient transfer of a shaped pulse to the first transducer.