Array sensor electronics

• US 7,378,856 B2
• Filed: 10/24/2002
• Issued: 05/27/2008
• Est. Priority Date: 10/24/2001
• Status: Expired due to Term

• Current Assignee: Pressure Profile Systems Inc. (PPS U.K. Limited)
• Original Assignee: Pressure Profile Systems Inc. (PPS U.K. Limited)
• Inventors: Peine, William, Pratico, Robert, Son, Jae S.
• Primary Examiner(s): Hirshfeld; Andrew H.
• Assistant Examiner(s): He; Amy
• Application Number:
  US10/493,459
• Publication Number:
  US 20050068044A1
• Time in Patent Office: 2,042 Days
• Field of Search: 324/661, 324/662, 324/686, 324/688, 324/616
• US Class Current: 324/662
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/043 in a linear array
• CPC Class Codes: A61B 5/037 Measuring oesophageal pressure
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells

Abstract

Circuits and methods for detecting and amplifying sensor and sensor array (102, 104) output signals are presented. According to some aspects, a nonlinear feedback loop containing a sensor element provides a nonlinear transformation that compensates for a corresponding nonlinear response of the sensor element thereby providing a linearized final output signal. In other aspects, idle sensors are coupled to a reference on non-idle sensor elements. Other aspects include sensor and amplification circuits which operate without traditional filtering or switching elements, such that a higher throughput is achieved and no settling time is required due to traditional transients, thus allowing for faster scanning of larger sensor arrays. Some embodiments of the present invention are directed to variable gap capacitive sensor arrays and the signal processing electronics.

Claims

1. A sensor system, comprising:

a sensor array having a plurality of sensor elements;

an input multiplexer and an output multiplexer configured to select a sensor element; and

an amplifier, disposed in a feedback arrangement around the sensor element and the input and output multiplexers, the amplifier receiving an input signal corresponding to an output of the sensor element and providing an output signal that drives the sensor element, wherein each sensor element has an individually-controlled gain or an individually-controlled offset.

2. The system of claim 1, wherein the sensor element comprises a capacitive sensor element and the sensor array comprises a capacitive sensor array.

3. The system of claim 1, wherein the sensor array comprises a first set of conductive strips crossing a second set of conductive strips to form each of the plurality of sensor elements at an intersection of a strip in the first set and a strip in the second set, the sensor array adapted and configured such that a stimulus alters a separation between a first conductive strip of the first set and a second conductive strip of the second set.

4. The system of claim 1, wherein the sensor array senses any of a force, a weight, a pressure and a displacement.

5. The system of claim 1, further comprising an amplitude detector which receives an output signal from the amplifier.

6. The system of claim 1, further comprising a nonlinear transformer which transforms a nonlinear output of the amplifier into a corresponding substantially-linear signal representing the stimulus.

7. The system of claim 6, wherein the nonlinear transformer is a feedback loop comprising the sensor element.

8. The system of claim 1, wherein the amplifier'"'"'s output signal is one of a plurality of signals which drive the sensor element.

9. The system of claim 1, further comprising a filtering circuit comprising a digitally-controlled integrator coupled to receive the output signal of the amplifier.

10. The system of claim 1, wherein a tunable filter element is coupled to the sensor element and wherein the tunable filter element is placed in physical proximity to the sensor elements to provide common mode rejection to environmental effects.

11. The sensor system of claim 1, further comprising a resistor disposed in the feedback arrangement in parallel with the selected sensor element.

13. The system of claim 1, further comprising a path from the sensor element to a common potential which is selectably coupled to the sensor element.

14. The system of claim 1, wherein the sensor element is selectably coupled to a ground potential when the sensor element is not being driven or sampled.

15. The system of claim 1 wherein the sensor element is coupled to an electrical line which is individually shielded from electromagnetic effects.

16. The system of claim 1, further coupled to at least one other sensor system such that the system of claim 1 and the at least one other sensor system cover a combined region of interest having a greater area than an area covered by the system of claim 1 or an area covered by the at least one other sensor system.

12. A sensor system, comprising:

a sensor array having a plurality of sensor elements;

at least one sensor element of the sensor array, having addressable connections designating the sensor element, that senses a stimulus;

an amplifier, disposed in a feedback arrangement around the sensor element, the amplifier receiving an input signal corresponding to an output of the sensor element and providing an output signal that drives the sensor element;

a tunable filter, coupled to an oscillator having an oscillator signal, which shifts a phase of the oscillator signal to provide a phase-shifted signal; and

a summing circuit which sums the amplifier output with the phase-shifted signal to substantially cancel out oscillator bias in a portion of the sensor system.

17. A method for measuring a stimulus on a sensor array, the sensor array comprising a first set of conductive strips crossing a second set of conductive strips to form a plurality of sensor elements, the method comprising, for each of a plurality of the sensor elements:

selecting the sensor element of the sensor array associated with a first conductive strip of the first set of conductive strips and a second conductive strip of the second set of conductive strips, the selecting comprising selecting the first conductive strip and the second conductive strip and an offset based on the selected sensor element;

generating a sensor element output signal on the first conductive strip, the sensor element output signal being representative of a distance between the first conductive strip and the second conductive strip;

amplifying the sensor element output signal to generate an amplified signal representative of a pressure on the sensor element with the selected offset; and

feeding back the amplified signal to the second conductive strip.

18. The method of claim 17, wherein:

the sensor has a non-linear response; and

feeding back the amplified signal comprises feeding back the amplified signal through a non-linear transformer feedback loop corresponding to the non-linear sensor response.

19. The method of claim 18, wherein the non-linear sensor response is a non-linear response to a pressure applied to the sensor element.

20. The method of claim 17, further comprising selectively coupling at least one sensor element in the sensor array to a common potential during a time period in which the selected sensor element is idle and at least one other sensor elements is being sampled.

21. The method of claim 20, wherein the common potential is a ground potential.

22. A method for measuring a stimulus on a sensor array composed of a first set of conductive strips crossing a second set of conductive strips to form a plurality of sensor elements, comprising:

selecting a sensor element of the sensor array associated with a first conductive strip of the first set of conductive strips and a second conductive strip of the second set of conductive strips;

generating a sensor element output signal on the first conductive strip;

amplifying the sensor element output signal to generate an amplified signal representative of a physical property;

feeding back the amplified signal to the second conductive strip;

providing an oscillating signal to drive the sensor element,

shifting a phase of the oscillating signal to provide a phase-shifted signal; and

summing the sensor element output and the phase-shifted signal to substantially cancel out oscillator bias in a portion of the sensor system.

23. A sensor system having an output indicating a sensed property, comprising:

a sensor array having a plurality of sensor elements;

an input multiplexer and an output multiplexer configured to select a sensor element;

an amplifier, disposed in a feedback arrangement around the sensor element and the input and output multiplexers, the amplifier receiving an input signal corresponding to an output of the sensor element and providing an output signal that drives the sensor element; and

an amplitude detector having an input and an output, the input being coupled to receive the output signal of the amplifier, the output of the amplitude detector being coupled to the output of the sensor system.

24. The sensor system of claim 23, wherein each of the sensor elements comprises a capacitive sensor and the amplitude detector comprises a non-linear element.

25. The sensor system of claim 24, wherein the amplitude detector comprises a rectifier.

26. The sensor system of claim 23, further comprising:

a summing circuit; and

an integrator stage,

wherein the input of the amplitude detector is coupled to receive the output signal of the amplifier through the summing circuit, and the output of the amplitude detector is coupled to the output of the sensor system through the integrator stage.

27. The sensor system of claim 26, further comprising an oscillator driving the selected sensor element, the oscillator also being coupled to the input of the summing circuit through a phase shifting circuit.

28. The sensor system of claim 27, wherein:

the amplifier is a first amplifier; and

the sensor system further comprises a second amplifier, the second amplifier being connected between the summing circuit and the amplitude detector.

29. The sensor system of claim 28, further comprising a resistor connected in parallel to a selected sensor element in the feedback arrangement.