Sensors for monitoring movements, apparatus and systems therefor, and methods for manufacture and use

• US 7,918,801 B2
• Filed: 12/29/2005
• Issued: 04/05/2011
• Est. Priority Date: 12/29/2005
• Status: Expired due to Fees

• Current Assignee: Medility, LLC
• Original Assignee: Medility, LLC
• Inventors: Cochran, William T.
• Primary Examiner(s): Marmor, II; Charles A
• Assistant Examiner(s): D'ANGELO, MICHAEL J
• Application Number:
  US11/321,161
• Publication Number:
  US 20070167879A1
• Time in Patent Office: 1,923 Days
• Field of Search: 600/304, 600/551, 600587-593, 600/437, 600/438, 600/459, 324/206, 32420711-20726, 73862331-862337
• US Class Current: 600/534
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/442 Evaluating skin mechanical properties, e.g. elasticity, hardness, texture, wrinkle assessment

Abstract

Sensors, apparatus, and methods for measuring movements are disclosed. The sensors include input and output windings wound about a common location and an armature is equally positioned relative to both windings movable to vary inductance reactance of the sensor. The mass of the sensor and the ease of movements are such that flexible membranes, such as skin, can be monitored with insignificant interference. The sensor can be included in “Band-aid” bandage arrangement in which the bandage backing can be removed and held in place on skin by the bandage. A monitoring circuit, responsive to the changes in sensor impedance, provides indications of the detected movements. The monitoring circuit includes an arrangement for self-adjusting parameters so that the system can be automatically preset and continually reset. The monitoring circuit includes a power savings arrangement.

Claims

1. A sensor system for monitoring the displacement between movable parts of an object comprising:

an electrical sensor comprising two components, one component being adapted to be positioned within the other for generally linear movement there between, and having input and output circuits, wherein the electrical impedance of the sensor changes as a function of the relative displacement between the components, the components of the sensor being adapted to be attached to different movable parts of the object for providing impedance changes corresponding to displacements;

a circuit for applying pulses to the input circuit wherein the output winding outputs decaying signals, the rate of decay being a function of the relative displacement between the components, and

a monitoring circuit is responsive to the output signal decay rate for providing indications of the displacements between the movable parts of the object,

wherein the sensor components comprises a coil having an input winding and an output winding and a magnetic core extending into the coil for generally linear relative movement there between,

wherein the inductance of the sensor changes as a function of the relative displacement between the core and the coil, the coil and core being adapted to be attached to different movable parts of the object,

wherein the monitoring circuit comprises a circuit for measuring the amplitude of the decaying signal after the application of the pulses to the sensor as an indication of the displacements,

wherein the monitoring circuit includes a storage circuit for storing the magnitudes of the decaying signals at selected times subsequent to the application of the electrical pulses,

wherein the monitoring circuit varies the relative timing between the application of the electrical pulses and the operation of the storage circuit, and

wherein the monitoring circuit comprises;

a circuit for amplifying the magnitude of the decaying signals and applying the value of the amplified signals at controlled times to the storage circuit;

a circuit for sensing when the values of the decaying signals from the amplifying circuit are in saturation or below a reference level, and

the control circuit is responsive to the sensing circuit to adjusts the controlled times in a direction so that the amplifier circuit operates between saturation and the reference level.

2. A sensor system as defined in claim 1 comprising:

an analog to digital converter circuit for converting the magnitudes of the storage circuit to digital form, and

the control circuit performs an analysis of the digital signals to determine when the magnitudes of the decaying signals fall within saturation and reference level operating range of the amplifying circuit.

3. A sensor system as defined in claim 2 wherein the control circuit determines when the magnitudes of the decaying signals from the amplifier approach saturation or the reference level for varying the relative timing between the application of the electrical pulses and the operation of the storage circuit.

4. A sensor system as defined in claim 3 comprising apparatus for providing a visual display of the magnitudes of the decaying signals stored in the storage circuit as an indication of the displacement between the movable portions of the object.

5. Monitoring apparatus for use with a sensor that includes at least two movable parts adapted to be attached to separate parts of an object, and wherein the electrical impedance of the sensor varies as a function of the disposition of the two parts relative to each other, the apparatus comprising:

a circuit for applying time separated electrical pulses to the sensor, and

a circuit for analyzing the response of the sensor to the electrical pulses in the form of a decaying signals, the duration of which is a function of the impedance of the sensor, to provide an indication of changes in the disposition between the movable parts,

wherein the analyzing circuit selects the timing for making subsequent measurements so that the level of magnitudes is within a predetermined range,

wherein the analyzing circuit comprises;

an amplifier circuit for amplifying the magnitude of the decaying signals, wherein the response of the amplifier is adapted to be driven into non-linear operation, and

wherein the predetermined range of magnitudes for selecting the timing falls within the linear operation of the amplifier; and

wherein the analyzing circuit determines when the output of the amplifier is driven near the non-linear operation of the amplifier to change the timing for subsequent measurements.

6. Monitoring apparatus for use with a sensor that includes at least two movable parts adapted to be attached to separate parts of an object, and wherein the electrical impedance of the sensor varies as a function of the disposition of the two parts relative to each other, the apparatus comprising:

a circuit for applying time separated electrical pulses to the sensor, and

a circuit for analyzing the response of the sensor to the electrical pulses in the form of a decaying signals, the duration of which is a function of the impedance of the sensor, to provide an indication of changes in the disposition between the movable parts, wherein the sensor includes a coil and a ferromagnetic core adapted to be located for movement within the coil, the coil and core being adapted to be attached to separate movable parts of an object, and the inductive reactance of the sensor varies as a function of the disposition of the coil and core relative to each other over the scope of movements, and wherein the analyzing circuit comprises;

one or more operation parameters, and

a control circuit programmed to process a range of signals from the sensor and for resetting the operation parameters of the analysis circuit in the event the sensor inductive reactance changes exceed the range.

7. Monitoring apparatus as defined in claim 6 where the analyzing circuit comprises an amplifier and the control circuit monitors the output of the amplifier circuit to determine when the range of amplified signals exceeds the linear operation of the amplifier for resetting the parameters of the analyzing circuit for amplifier linear operation.

8. Monitoring apparatus as defined in claim 7 wherein the amplifier is a variable gain amplifier, and the control circuit monitors the output of the amplifier circuit to modify the gain of the amplifier if the amplifier operates at levels approaching saturation or zero.