System for identifying a cable transmitting a signal from a sensor to an electronic instrument

• US 6,497,659 B1
• Filed: 04/09/1999
• Issued: 12/24/2002
• Est. Priority Date: 04/09/1999
• Status: Expired due to Fees

• Current Assignee: Spacelabs Healthcare LLC (OSI Systems Incorporated)
• Original Assignee: Spacelabs Medical Incorporated (OSI Systems Incorporated)
• Inventors: Rafert, Stephen C.
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): KREMER, MATTHEW J
• Application Number:
  US09/289,792
• Time in Patent Office: 1,355 Days
• Field of Search: 600/309-311, 600/322-324, 600/331, 600/364, 600/365-366, 324/680, 324/610, 324/648, 324/651, 324/657, 324/666, 324/673, 324/706, 324/725, 439/620
• US Class Current: 600/331
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 2562/222 Electrical cables or leads therefor, e.g. coaxial cables or ribbon cables
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: G01R 31/60 Identification of wires in a multicore cable

Abstract

A system is described for identifying a cable transmitting a signal from a sensor to an electronic instrument. The cable includes a reactance element such as a capacitor or an inductor. The system identifies the cable by applying a voltage to a combination of a resistance and the reactance element to measure the reactance of the reactance element either alone or in combination with the resistance.

Claims

1. A cable for connecting a sensor to an electronic instrument, comprising:

an elongated signal conduit extending between a sensor terminal adapted for connection to the sensor and a signal terminal;

a connector attached to the signal conduit adjacent the signal terminal, the connector being attachable to the instrument to permit signal communication between the instrument and the sensor through the connector, the signal conduit, and the sensor terminal; and

a reactance element coupled to at least one resistor to form a network having a predetermined time constant, the network being coupled to the instrument through a plurality of terminals of the connector, the instrument being configured to apply a signal to the network having a single polarity, and to measure a corresponding response in the network that is a function of a predetermined time constant.

2. The cable of claim 1 wherein the elongated signal conduit is comprised of one or more conductive wires.

3. The cable of claim 1 wherein the elongated signal conduit is comprised of one or more optical fibers.

4. The cable of claim 1 wherein the reactance element is mounted in the connector.

5. The cable of claim 1 wherein the reactance element is mounted in the signal conduit.

6. The cable of claim 1 wherein the signal conduit comprises:

a sensor cable adapted for coupling to a sensor at one end and to a sensor connector at the other end; and

an adapter cable adapted for coupling to the connector at one end and to the sensor connector at the other end.

7. The cable of claim 6 wherein the reactance element is mounted in the adapter cable.

8. The cable of claim 6 wherein the reactance element is mounted in the sensor cable.

9. The cable of claim 1 wherein the reactance element is a capacitor.

10. The cable of claim 1 wherein the reactance element is an inductor.

11. The cable of claim 1, further comprising a switch having one of two states wherein the state of the switch changes over a selected time interval in response to a signal from the reactance element, the time interval being a function of the predetermined time constant.

12. A connector for joining a cable to an electronic instrument, the cable transmitting a signal to the instrument, the connector comprising:

a connector body attached to an end of the cable;

a plurality of terminals in the connector body adapted to be coupled to the instrument; and

a reactance element coupled to at least one resistor to form a network having a predetermined time constant, the network being positioned in the connector body and coupled between the terminals, the instrument being operable to apply a signal to the network and operable to measure a corresponding response in the network, the response being a function of the predetermined time constant.

13. The connector of claim 12 wherein the reactance element is a capacitor.

14. The connector of claim 12 wherein the reactance element is an inductor.

15. The connector of claim 12, further comprising a switch having one of two states wherein the state of the switch changes in response to a signal from the reactance element over a selected time interval, the time interval being a function of the predetermined time constant.

16. A system for providing information based on a sensor signal from a sensor, comprising:

a cable including an elongated signal conduit adapted for coupling to a sensor at one end and to a signal terminal at the other end, the elongated signal conduit adapted for coupling a sensor signal from the sensor terminal to the signal terminal;

a connector attached to the cable adjacent to the signal terminal, the connector having a plurality of terminals;

a reactance element coupled to at least one resistor to form a network having predetermined reactance characteristics that is coupled between selected terminals of the connector; and

an electronic instrument coupled to the terminals in the connector, the instrument being adapted to provide the information as a function of the sensor signal and to apply a signal to the network having a single polarity to identify the cable based on a measurement of a selected time interval, the time interval being a function of the predetermined reactance characteristics of the network.

17. The system of claim 16 wherein the reactance element is a capacitor.

18. The system of claim 16 wherein the reactance element is an inductor.

19. The system of claim 16 wherein the instrument comprises:

a microprocessor coupled to one or more of the terminals in the connector to receive the sensor signal, the microprocessor being adapted to provide the information as a function of the sensor signal;

a display coupled to the microprocessor to receive and display the information; and

a measurement circuit coupled to exchange signals with the microprocessor, the measurement circuit being coupled to receive the selected ones of the terminals in the connector so that the measurement circuit is adapted to measure a selected time interval, the time interval being a function of the predetermined reactance characteristics of the network and determined in response to a command signal from the microprocessor.

20. The system of claim 19 wherein the measurement circuit comprises:

a first circuit coupled between the microprocessor and the selected ones of the terminals in the connector to provide a voltage having a single polarity from the microprocessor to the network, the microprocessor applying the voltage to the network and interrupting the voltage at a first time; and

a trigger circuit for sensing a voltage in the reactance network, the trigger circuit supplying a trigger signal to the microprocessor when the voltage in the reactance element equals a threshold voltage at a second time, the difference between the first time and the second time being the selected time interval.

21. The system of claim 19, further comprising:

a switch coupled between a plurality of terminals in the connector having one of two states wherein the state of the switch changes over the selected time interval in response to a signal from the reactance network, the time interval being a function of the selected reactance characteristics.

22. The system of claim 21 wherein the measurement circuit comprises:

a conductive coupling between the microprocessor and the reactance element adapted to provide a first voltage from the microprocessor to the reactance element; and

a voltage source and a current detector coupled in series with the switch through the terminals in the connector, the current detector providing a detection signal to the microprocessor when the state of the switch changes.

23. The system of claim 19 wherein the measurement circuit comprises:

a conductive coupling between the microprocessor and the reactance element adapted to provide a first voltage from the microprocessor to the reactance element;

a switch having one of two states wherein the state of the switch changes over a selected time interval in response to a signal from the network, the time interval being a function of the selected reactance characteristics of the network; and

a voltage source and a current detector coupled in series with the switch, the current detector providing a detection signal to the microprocessor when the state of the switch changes.

24. The system of claim 16 wherein the network is mounted in the connector.

25. The system of claim 16 wherein the network is mounted in the cable.

26. The system of claim 16 further comprising a sensor coupled to the cable, and wherein the network is mounted in the sensor.

27. The system of claim 16 wherein the electronic instrument further includes an operating feature or mode that is enabled by an enable signal, and wherein the electronic instrument is constructed to generate the enable signal as a function of the identification of the cable.

28. The system of claim 27 wherein the electronic instrument comprises a pulse oximetry monitor.

29. The system of claim 28 wherein the feature of the pulse oximetry monitor enabled by the enable signal is a noise or artifact rejecting algorithm.

30. The system of claim 29 wherein the feature enabled by the enable signal is a noise or artifact rejecting algorithm.

31. The system of claim 28 wherein the cable comprises:

a sensor cable adapted for coupling to the sensor at one end and to a sensor connector at the other end; and

an adapter cable adapted for coupling to the connector at one end and to the sensor connector at the other end.

32. The system of claim 16 wherein the network is mounted in the adapter cable.

33. The system of claim 31 wherein the network is mounted in the sensor cable.

34. The system of claim 31 wherein the network is mounted in the sensor connector.

36. The method of claim 29 wherein the step of providing a first voltage to the network comprises the step of providing a first voltage to a capacitor.

37. The method of claim 29 wherein the step of providing a first voltage to the network comprises the step of providing a first voltage to a resistor coupled to a capacitor.

38. The method of claim 29 wherein the step of providing a first voltage to the network reactance element comprises the step of providing a first voltage to an inductor.

39. The method of claim 29 wherein the step of providing a first voltage to the network comprises the step of providing a first voltage to a resistor coupled to an inductor.

40. The method of claim 29 wherein the step of monitoring a second voltage in the network comprises the steps of:

coupling the second voltage to a switch to control a state of the switch;

detecting when the state of the switch changes; and

determining a time interval between the step of providing a first voltage and the detection of the changed state of the switch.

41. The method of claim 40 wherein the step of detecting when the state of the switch changes comprises the steps of:

applying a voltage to a circuit coupled to the switch; and

detecting a change in current in the circuit when the state of the switch changes.

35. A method for identifying a cable having a reactance network with selected reactance characteristics, the method comprising the steps of

providing a first voltage to the network, wherein the first voltage has a single polarity;

monitoring a second voltage in the network to detect a rate of change of the second voltage; and

comparing the rate of change of the second voltage to a predetermined rate and identifying the cable based on the comparison.

42. A method for identifying a cable having an inductor coupled to a resistor to form a network having selected reactance characteristics, the method comprising the steps of:

coupling the network to a bridge circuit;

applying an alternating current signal to the bridge circuit; and

generating an identification signal when the reactance characteristics of the network match predetermined reactance characteristics.

43. A method for analyzing a sensor signal generated by a sensor and transmitted by a cable, the cable having a reactance element with selected reactance characteristics, the method comprising the steps of:

coupling the cable to an electronic instrument such that the instrument receives the sensor signal;

providing a first voltage to the reactance element the first voltage having a single polarity;

monitoring a second voltage in the reactance element to detect a rate of change of the second voltage;

comparing the rate of change of the second voltage to a predetermined rate and identifying the cable based on the comparison; and

analyzing the sensor signal in the instrument based on the identification of the cable.

44. The method of claim 43 wherein the step of coupling the cable comprises the step of coupling the cable to an electronic instrument having a microprocessor such that the microprocessor receives the sensor signal.

45. The method of claim 44 wherein the step of monitoring a second voltage comprises the step of monitoring a second voltage in the reactance element with a software routine carried out in the microprocessor.

46. The method of claim 45 wherein the step of comparing the rate of change comprises the steps of:

generating a trigger signal when the second voltage equals a threshold voltage; and

identifying the cable in the software routine according to a time interval between the provision of the first voltage and the generation of the trigger signal.

47. The method of claim 46 wherein the step of analyzing the sensor signal comprises the step of analyzing the sensor signal in the microprocessor according to the software routine.

48. The method of claim 44 further comprising:

enabling an operating feature or mode of the electronic instrument as a function of analyzing the identification of the cable.

49. The method of claim 49 wherein the electronic instrument comprises a pulse oximetry monitor.

50. The method of claim 49 wherein the enabling of an operating feature or mode of the electronic instrument comprises enabling a noise or artifact rejecting algorithm in the electronic instrument.

51. A system for providing information based on a sensor signal from a sensor, comprising:

a cable including an elongated signal conduit adapted for coupling to a sensor at one end and to a signal terminal at the other end, the elongated signal conduit adapted for coupling a sensor signal from the sensor terminal to the signal terminal;

a connector attached to the cable adjacent to the signal terminal, the connector having a plurality of terminals;

an inductor coupled to at least one resistor to form a network having predetermined reactance characteristics that is coupled between selected terminals of the connector; and

an electronic instrument coupled to the terminals in the connector, the instrument being adapted to provide the information as a function of the sensor signal and to identify the cable based on a measurement of selected reactance characteristics, the instrument further comprising a microprocessor coupled to one or more of the terminals in the connector to receive the sensor signal, a display coupled to the microprocessor, and a measurement circuit coupled to exchange signals with the microprocessor, wherein the measurement circuit is comprised of a bridge circuit coupled to receive an alternating current signal from the microprocessor, the bridge circuit having a detector outputting a detection signal to the microprocessor and being coupled to receive the selected ones of the terminals in the connector so that the bridge circuit is adapted to detect the reactance characteristics of the network and generate the detection signal in response to the reactance characteristics.

52. A method for identifying a cable having a reactance element with selected reactance characteristics, the method comprising the steps of. providing a first voltage to the reactance element, wherein the reactance element includes an inductor;

monitoring a second voltage in the reactance element to detect a rate of change of the second voltage; and

comparing the rate of change of the second voltage to a predetermined rate and identifying the cable based on the comparison.

53. The method of claim 52 wherein the step of monitoring a second voltage in the reactance element comprises the steps of:

coupling the second voltage to a switch to control a state of the switch;

detecting when the state of the switch changes; and

determining a time interval between the step of providing a first voltage and the detection of the changed state of the switch.

54. The method of claim 52 wherein the step of detecting when the state of the switch changes comprises the steps of:

applying a voltage to a circuit coupled to the switch; and

detecting a change in current in the circuit when the state of the switch changes.

55. A method for identifying a cable having a reactance element with selected reactance characteristics, the method comprising the steps of:

providing a first voltage to the reactance element, wherein the reactance element includes an inductor coupled to a resistor;

monitoring a second voltage in the reactance element to detect a rate of change of the second voltage; and

comparing the rate of change of the second voltage to a predetermined rate and identifying the cable based on the comparison.

56. The method of claim 55 wherein the step of monitoring a second voltage in the reactance element comprises the steps of:

coupling the second voltage to a switch to control a state of the switch;

detecting when the state of the switch changes; and

determining a time interval between the step of providing a first voltage and the detection of the changed state of the switch.

57. The method of claim 56, wherein the step of detecting when the state of switch changes comprises the steps of:

applying a voltage to a circuit coupled to the switch; and

detecting a change in current in the circuit when the stage of the switch changes.