Micropower differential sensor measurement

• US 20020190785A1
• Filed: 08/09/2002
• Published: 12/19/2002
• Est. Priority Date: 01/24/2000
• Status: Active Grant

• Current Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Original Assignee: Christopher P. Townsend, Michael John Hamel, Steven W. Arms
• Inventors: Arms, Steven W., Townsend, Christopher P., Hamel, Michael John
• Granted Patent: US 6,714,763 B2
• Time in Patent Office: Days
• US Class Current: 327/588
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Abstract

A sensing device includes a Wheatstone bridge and a source of a stimulation configured to apply the stimulation across two electrodes of the Wheatstone bridge. The device also includes a timing sensitive circuit configured to detect timing of a signal appearing across one of the other electrodes of the bridge as a result of the stimulation being applied. The timing provides a way to read the sensor. The device can be powered remotely and data so read can be transmitted using the remote power. The timing sensitive circuit includes a comparator. The comparator provides a high logic signal for a time related to the reactance of one leg of the Wheatstone bridge, and that provides a reading of a differential sensor having elements in each leg of the bridge.

Claims

1. An electronic circuit, comprising:

a first electrode, a second electrode, a third electrode and a fourth electrode;

a differential sensor comprising a first variable element connected to a second variable element at said first electrode, said first a variable element also connected to said second electrode, said second variable element also connected to said third electrode;

a fixed device connected between said second electrode and said fourth electrode;

a source of a stimulation connected to apply a stimulation across said first and said fourth electrodes; and

a timing sensitive circuit configured to measure timing of a signal appearing at said second electrode that arises from said stimulation applied across said first and fourth electrodes.

2. The electronic device as recited in claim 1, wherein said first variable element comprises a variable capacitor, a variable inductor, or a variable resistor.

3. The electronic device as recited in claim 2, further comprising a Wheatstone bridge wherein said Wheatstone bridge comprises a first leg and a second leg, said first leg comprising said first variable element, said second electrode, a first fixed device, and said fourth electrode, said second leg comprising said first electrode, said second variable element, said third electrode, said second fixed device, and said fourth electrode.

4. The electronic device as recited in claim 3, wherein said first variable element is connected between said first electrode and said second electrode, said first fixed device is connected between said second electrode and said fourth electrode, said second variable element is connected between said first electrode and said third electrode, and said second fixed device is connected between said third electrode and said fourth electrode.

5. The electronic device as recited in claim 4, wherein said Wheatstone bridge comprises a pair of variable capacitors or a pair of variable inductors wherein a first capacitor of said pair of capacitors or a first inductor of said pair of inductors is in said first leg and a second capacitor of said pair of capacitors or a second inductor of said pair of inductors is in said second leg.

6. The electronic device as recited in claim 5, wherein said first and second fixed devices comprise a pair of fixed matched resistors, wherein a first resistor of said pair of matched resistors is in said first leg and a second resistor of said pair of matched resistors is in said second leg.

7. The electronic device as recited in claim 4, wherein said first and second variable elements comprise a pair of variable resistors, wherein a first variable resistor of said pair of variable resistors is in said first leg and a second variable resistor of said pair of variable resistors is in said second leg.

8. The electronic device as recited in claim 7, wherein said Wheatstone bridge further comprises a pair of fixed matched capacitors or a pair of fixed matched inductors wherein a first capacitor of said pair of fixed matched capacitors or a first inductor of said pair of fixed matched inductors is in said first leg and a second capacitor of said pair of fixed matched capacitors or a second inductor of said pair of fixed matched inductors is in said second leg.

9. The electronic device as recited in claim 1, wherein said source of said stimulation comprises a pulse generator.

10. The electronic device as recited in claim 9, wherein said pulse generator comprises a microprocessor controlled by software.

11. The electronic device as recited in claim 9, wherein said pulse generator comprises a discrete pulse generator.

12. The electronic device as recited in claim 9, wherein said stimulation comprises a leading edge, wherein said leading edge sets said timing sensitive circuit.

13. The electronic device as recited in claim 1, wherein said timing sensitive circuit is sensitive to a reactive time constant.

14. The electronic device as recited in claim 13, wherein said first leg comprises a larger reactance than said second leg and wherein said timing sensitive circuit measures a timing related to said first leg.

15. The electronic device as recited in claim 14, wherein said timing sensitive circuit further comprises a comparator.

16. The electronic device as recited in claim 15, wherein said comparator is configured to provide magnitude of change of said sensor from said timing.

17. The electronic device as recited in claim 16, wherein said comparator outputs a square pulse signal, wherein said signal lasts for a time proportional to said reactive time constant of said first leg of said Wheatstone bridge.

18. The electronic device as recited in claim 15, wherein said timing sensitive circuit comprises a pair of comparators.

19. The electronic device as recited in claim 18, wherein said pair of comparators are configured to provide both direction and magnitude of change of said sensor elements.

20. The electronic device as recited in claim 18, wherein said pair of comparators are configured as a set-reset latch.

21. The electronic device as recited in claim 1, wherein said timing sensitive circuit measures analog position of said first variable element.

22. The electronic device as recited in claim 1, further comprising a circuit for reading timing information from said comparator and providing a signal with data from said comparator encoded for external transmission.

23. The electronic device as recited in claim 22, wherein said signal for external transmission is provided to a coil for external transmission.

24. The electronic device as recited in claim 22, wherein said signal for external transmission is used to modulate a radio transmitter carrier wave for radio transmission to a remote radio receiver.

25. The electronic device as recited in claim 24, further comprising a receive coil to wirelessly receive power wherein power received by said receive coil also supplies power to said radio transmitter.

26. The electronic device as recited in claim 22, wherein said data further comprises address information identifying the electronic device transmitting data.

27. The electronic device as recited in claim 1, further comprising a remote power source for powering the electronic device.

28. The electronic device as recited in claim 27, wherein said remote power source comprises a source of electromagnetic radiation directed at a receive coil connected to a rectifier in the electronic device.

29. The electronic device as recited in claim 28, wherein said rectifier is connected to said source of stimulation and to said timing sensitive circuit to provide power for their operation.

30. The electronic device as recited in claim 28, wherein said remote power source further comprises a coil for receiving information from the electronic device.

31. The electronic device as recited in claim 1, wherein said differential sensor is a peak strain detection linear displacement sensor.

32. The electronic device as recited in claim 1, further comprising an ID generator to identify which sensor is being interrogated.

33. A method of reading a sensor comprising the steps of:

a) providing a differential sensor having a first variable element and a second variable element;

b) providing a comparator; and

c) providing a signal to said first variable element wherein said sensor produces an output depending on magnitude of said first variable element, and using said comparator for providing a signal that is a measure said magnitude.

34. The method as recited in claim 33, wherein said first variable element is a resistor, a capacitor or an inductor and said magnitude is a resistance, capacitance, or inductance.

35. The method as recited in claim 33, wherein a second comparator is connected to said second variable element.

36. The method as recited in claim 33, wherein said signal comprises a pulse.

37. The method as recited in claim 33, wherein a single pulse is sufficient to read said sensor.

38. The method as recited in claim 33, wherein said output depends on a time constant of a reactive element.

40. The method as recited in claim 39, wherein said reading depends on a time constant of a reactive element.

41. The method as recited in claim 39, further comprising the step of generating an ID for inclusion with said data.

39. A method of using an electronic circuit, comprising the steps of:

a) providing a circuit comprising a sensor, a circuit for reading said sensor, and a circuit for transmitting data;

b) wirelessly providing power to said circuit from a remote source of power;

c) sensing a change in an environmental condition with said sensor;

d) reading said sensor with said circuit for reading said sensor, wherein only a single pulse stimulation signal to said sensor is needed to read said sensor;

e) providing said reading to a transmitting circuit; and

f) transmitting said data with said transmitting circuit.