WO2015009315A1

WO2015009315A1 - Cable detection system and method

Info

Publication number: WO2015009315A1
Application number: PCT/US2013/051262
Authority: WO
Inventors: Derek Yong QIN
Original assignee: Draeger Medical Systems, Inc.
Priority date: 2013-07-19
Filing date: 2013-07-19
Publication date: 2015-01-22

Abstract

A cable detection system and method for detecting a type of cable connected to a patient monitoring device is provided. An AC signal generator generates an input electrical AC signal. A switch selectively connects the AC signal generator or ground with one of a first lead of the cable. A component is coupled to a second lead of the cable and a detector coupled to the second lead of the cable detects an AC output signal and DC signal on the second lead. A controller controls the switch to operate in one of a first position coupling the AC signal generator with the first lead enabling the detector to measure the AC output signal and determine an AC condition associated with the cable and a second position coupling the first lead to ground enabling the detector to measure the DC signal and determine a DC condition associated with the cable. The controller uses the determined AC condition and DC condition associated with the cable to identify the type of cable connected to the patient monitoring device.

Description

Cable Detection System and Method

FIELD OF THE INVENTION

The present invention relates generally to the field of electronic devices and, more particularly, to a scheme for detecting a type of cable that connects an electronic device to an object.

BACKGROUND OF THE INVENTION

The use of electronic devices to perform any number of tasks has steadily increased over time. This is especially true in the field of providing healthcare to patients. In the medical field, patient monitoring devices and/or systems are selectively coupled to a patient via at least one sensor which senses information from the patient that is used in deriving at least one physiological parameter associated with the patient. Often times, these sensors are coupled to the patient monitoring devices using a multi-conductor cable which is interconnected to the patient monitor so that data representing the at least one physiological parameter may be selectively displayed to a healthcare provider (e.g. doctor, nurse, etc) on one of the patient monitoring device and/or at a central monitoring station for the particular unit in which the patient is presently located. To ensure that the data acquired from the patient is processed correctly to derive the desired patient parameter data, it may be necessary to identify a type of cable that interconnects the patient and the patient monitoring device. This is particularly useful when the cable connecting the patient-connected sensors with the patient monitoring device is a multi-conductor cable, and the number of conductors supported is a variable.

There have been different attempts at providing a scheme for detecting the presence and type of cable connected to a patient monitoring device. One mechanism employed is to provide one or two dedicated conductor(s) within the multi-conductor cable that is solely responsible for providing cable information to the patient monitoring device. A drawback associated with this scheme is the increased additional cost and design associated with producing a cable having a dedicated conductor. Moreover, in some situations the inclusion of additional conductors and connector pins may be either undesirable or impossible. Another option, albeit a similarly costly one, is the use of a mechanical switch or sensor to determine the presence of a cable. Additionally, as this scheme includes mechanical components (e.g. the switch), this scheme also has an unacceptable degree of unreliability associated with it. A further drawback associated with both of these cable detection schemes is the need to include additional components within the cable itself that provide the requisite information to the patient monitoring device in order to allow the patient monitoring device to detect and identify the cable. Furthermore, the above discussed cable detection schemes are not easily retrofitted into existing connector forms.

Another cable detection scheme overcomes certain deficiencies associated with the above discussed cable detection schemes. This scheme identifies the presence and type of cable connected to a cable connector by generating an alternating current (AC) signal and applying the generated AC signal to a first conductor of the cable. The AC signal is detected at a second conductor of the cable to produce a detected signal. A characteristic of the detected signal is compared with a threshold value and the proper interconnection of the cable and cable connector is identified based on the comparison. Thereafter, the AC signal is sequentially applied to a plurality of conductors of the cable and the cable type is determined based on an amplitude dependent characteristic of the detected signal. While this scheme offers an improvement over other cable detection schemes, there are still drawbacks associated with it. One drawback of this cable detection scheme relates to the misidentification of the cable type when an intermediate cable is coupled between the cable and the cable connector. Therefore, a need exists to produce a cable detection scheme that can consistently identify the presence and type of cable connected to the patient monitoring device despite the presence or absence of an intermediate extension cable. A system according to invention principles addresses the deficiencies associated with identifying the presence and type of cable connected to an electronic patient monitoring device.

SUMMARY OF THE INVENTION

In one embodiment, a cable detection system for detecting a type of cable connected to a patient monitoring device is provided. An AC signal generator generates an input electrical AC signal. A switch selectively connects the AC signal generator with one of a first lead of the cable. A component is coupled to a second lead of the cable and a detector coupled to the second lead of the cable detects an AC output signal and DC signal on the second lead. A controller controls the switch to operate in one of a first position coupling the AC signal generator with the first lead enabling the detector to measure the AC output signal and determine an AC condition associated with the cable and a second position coupling the first lead to ground enabling the detector to measure the DC signal and determine a DC condition associated with the cable. The controller uses the determined AC condition and DC condition associated with the cable to identify the type of cable connected to the patient monitoring device. In another embodiment, the controller sequentially controls the switch to move between the first position and second position to individually couple the first lead of each independently shielded conductor with one of the AC signal generator and ground enabling the detector to measure the AC output signal and DC signal for each independently shielded conductor, the controller determines the AC condition and DC condition associated with each of the independently shielded conductors and uses the AC condition and DC condition of each independently shielded conductor to identify a type of cable connected to the patient monitoring device.

In another embodiment, a method of detecting a type of cable connected to a patient monitoring device is provided. The method includes generating an input electrical AC signal by an AC signal generator and selectively controlling a switch to move between a first position connecting the AC signal generator with a first lead and a second position connecting the first lead to ground. An AC output signal is detected and measured on a second lead when the switch is in the first position and an AC condition associated with the cable is determined. A DC signal is detected and measured through a resistor coupled to the second lead when the switch is in the second position and a DC condition associated with the cable is determined. The determined AC condition and DC condition associated with the cable are used to identify the type of cable connected to the patient monitoring device.

In a further embodiment, the cable is a multi conductor cable including a plurality of independently shielded conductor, each independently shielded conductor having a first lead and a second lead. The method further includes sequentially controlling the switch to move between the first position and second position to individually couple the first lead of each independently shielded conductor with one of the AC signal generator and ground and measuring the AC output signal and DC signal for each independently shielded conductor. The AC and DC condition associated with each of the independently shielded conductors is determined and the AC condition and DC condition of each independently shielded conductor is used to identify a type of cable connected to the patient monitoring device.

In another embodiment, a multi-conductor cable is provided. The multi-conductor cable includes a plurality of independently shielded conductors, each independently shielded conductor including a central conductor and a shield substantially surrounding the central conductor. A plurality of sensors sense data from an object, each of the plurality of sensors coupled to respective ones of the plurality of independently shielded conductor. A connector has a plurality of pins, each of the plurality of independently shielded conductors terminating at a respective one of the plurality of pins, the connector enabling connection of the multi- conductor cable with an electronic device and having at least two independently shielded conductors short circuited.

In yet another embodiment, a multi-conductor electrocardiogram (ECG) cable is provided. The ECG cable includes a plurality of independently shielded conductors, each independently shielded conductor including a central conductor and a shield substantially surrounding the central conductor. A plurality of electrodes are provided for sensing electrophysiological signals from a patient, each of the plurality of electrodes coupled to respective ones of the plurality of independently shielded conductors. A connector has a plurality of pins, each of the plurality of independently shielded conductors terminating at a respective one of the plurality of pins, the connector enabling connection of the multi- conductor ECG cable with an electrocardiogram monitoring device and having a respective independently shielded conductor configured to communicate data associated with the V5 lead in an ECG lead configuration short circuited indicating that the multi-conductor ECG cable is a 5 lead ECG cable.

BRIEF DESCRIPTION OF THE DRAWING

Figures 1A - 1C are illustrative views of cable connectors positioned at respective ends of a cable used with the cable detection system according to invention principles;

Figures 2A - 2C are wiring diagrams for the cables shown in Figures 1A - 1C for use with the cable detection system according to invention principles;

Figures 3A and 3B are illustrative views of the interconnection between cables and a patient monitoring device that includes the cable detection system according to principles of the present invention;

Figure 4 is a block diagram of the cable detection system according to invention principles;

Figure 5 is a circuit diagram detailing an aspect of the cable detection system according to invention principles; and

Figure 6 is a flow diagram detailing an algorithm used by the cable detection system to determine the presence and type of cable connected to a particular patient monitoring device according to invention principles. DETAILED DESCRIPTION OF THE INVENTION

A system that detects the presence and type of cable connected to a patient monitoring device is provided. The patient monitoring device may be any device that is coupled to a patient by at least one sensor via a cable including at least one shielded conductor. The patient monitoring device is able to receive and process data sensed by the at least one sensor which is communicated to the patient monitoring device via the at least one shielded conductor of the cable. The shield of each of the at least one shielded conductors are independent from one another and only shield one respective conductor. The cable may include a connector at an end thereof for connecting the cable to a mating connector on the patient monitoring device. The connector may include a number of pins (or other electrical contacts) corresponding to a number of shielded conductors within the cable such that signals communicated by the respective shielded conductor is provided to the patient monitoring device via its respective pin for further processing.

An exemplary embodiment may include an ECG monitoring device that senses electrophysiological signals from a patient via a set of electrodes (sensors) wherein the sensed electrophysiological signals are communicated via the at least one shielded conductor and are processed in a known manner to derive ECG data for the particular patient. In this embodiment, the cable may include at least six independently shielded conductors (e.g. coaxial cables) such that each respective conductor has its own shield which is not tied to or connected to any other shield of any other conductor inside the cable. Each of the at least six individual shielded conductors terminates at a connector having at least six pins which may be received within the mating connector on the ECG monitoring device enabling electrophysiological signals sensed by the electrodes to be received and processed by the ECG monitoring device in a known manner to derive ECG data for the particular patient.

Often times the cable connecting the patient monitoring device to the patient is a multi-conductor cable that does not have all the lead/channels which the monitoring device allowed. It is important for the patient monitoring device to know what type of cable is connected and how many of the conductors within the cable exist for communicating data sensed by the sensors to the patient monitoring device. Without knowing the configuration of the cable including the number of active conductors, the patient monitoring device may incorrectly process the data resulting in erroneous patient parameter data. In other instances, when the patient monitoring device senses a conductor that is inactive, the patient monitoring device may issue an erroneous alarm indicative of a condition that does not actually exist and provide an erroneous and unnecessary notification to a care provider (e.g. doctor, nurse, etc) that would require the care provider to respond when nothing is actually wrong. One manner of detecting and identifying a type of cable including a number of conductors that are actively communicating data sensed by the sensors to the patient monitoring device includes injecting an AC signal onto one lead (e.g. shield or central conductor) of the cable and detecting and measuring the AC current output on another lead of the cable (shield or central conductor). The AC signal output is derived by the capacitive coupling between the two leads of the cable. The determination of the presence and type of cable is made by detecting an amplitude dependent characteristic associated with the AC output on the other lead and comparing the detected amplitude dependent characteristic with a threshold to determine if the lead is active and able to communicate data thereon. An exemplary mechanism for detecting the presence and type of cable by injecting AC signal and measuring the capacitive coupling between leads is disclosed in US Patent No. 7,902,810 which is commonly owned by the applicant of the present cable detection system and is incorporated in its entirety by reference. This advantageously enables the patient monitoring device to identify the number of conductors in a particular cable.

While the AC injection cable detection scheme accurately identifies the presence and type of cable connected to the patient monitoring device, a problem presents itself when the cable having the sensors at one end and the connector at the other end is coupled to the patient monitoring device via an intermediate cable. Hereinafter, the cable that includes the sensors will be referred to as a sensor cable. Additionally, the intermediate cable may be an extension cable that allows the patient to be positioned further away from the patient monitoring device. The intermediate cable includes six individually shielded conductors so that it can be used with 3 lead, 5 lead and 6 lead sensor cables. The intermediate cable includes a female connector that receives the pins of the sensor cable at one end and a male connector including a same number of pins for connecting the intermediate cable to the patient monitoring device at the other end. When the intermediate cable is connected and AC signal source is injected as discussed above, the resulting detected amplitude dependent characteristics for each lead is substantially the same because there is always capacitive coupling on all leads of the intermediate cable. Thus, the patient monitoring device would be unable to sense the presence of the cable and detect the type of cable because the detected amplitude dependent characteristics results in a determination that all leads are active in view of their capacitive coupling.

The present cable detection system advantageously enables the patient monitoring device to accurately detect the presence and identify the type of cable connected thereto when the sensor cable is directly connected to patient monitoring device and an intermediate cable connects the sensor cable to the patient monitoring device. The present cable detection system utilizes a cable that has an inactive central conductor pin (e.g. conductors in the cable that will not communicate data) short circuited. For example, to achieve the short circuit, the center conductor pin may be connected to its respective shield pin. Moreover, in arrangements such as these, no central conducting wire is present. This is described for purposes of example only and any manner of short circuiting the central conductor may be implemented.

The cable detection system advantageously employs the existing AC detection in conjunction with a DC measurement to determine the presence and type of cable connected to the patient monitoring device. Moreover, the DC measurement taken by the patient monitoring device may use existing circuitry within the patient monitoring device to obtain the measurement of the DC voltage on a particular lead. The cable detection system uses the amplitude dependent characteristics detected on the AC output signal and the value of the DC measurement to determine the type of cable connected to the patient monitoring device. The cable detection system uses a DC threshold to which the DC measurement is compared to determine a DC condition associated with the particular lead being measured. The DC condition may be one of (a) a first DC condition when the measured DC value is greater than the DC threshold; or (b) a second DC condition when the measured DC value is less than or equal to the DC threshold. The cable detection system compares the detected amplitude dependent characteristic based on the capacitive coupling of the lead to a first AC threshold and a second AC threshold, the first AC threshold having a lower value than the second AC threshold, to determine an AC condition associated with the particular lead being measured. The determined AC condition based on the measured amplitude dependent characteristic is one of (a) a first AC condition when the amplitude dependent characteristic is less than or equal to the first AC threshold; (b) a second AC condition when the amplitude dependent characteristic is greater than the second AC threshold; and (c) a third AC condition when the amplitude dependent characteristic has a value that is greater than the first AC threshold but less than or equal to the second AC threshold.

Using the determined DC and AC conditions for each lead, the system is able to advantageously identify the presence of a particular lead whether or not an extension cable is present as well as whether or not the particular lead is connected to the patient at the time the AC and DC condition was determined. The manner in which the identified AC and DC conditions are used to determine the presence and type of cable will be further discussed below.

Figures 1A - 1C represent exemplary cables for use with the cable detection system according to invention principles. The respective configuration of each of these cables advantageously enables the cable detection system to determine the presence and type of cable that is connected to the patient monitoring device. This determination is still valid even when the respective cable is not directly connected to the patient monitoring device but rather is coupled thereto via an intermediate cable.

Figure 1A depicts an exemplary multi-conductor cable 100a. The multi-conductor cable 100 a includes a plurality of independently shielded conductors that each includes a center conductor able to transmit electrical signal and a shield that surrounds the center conductor which is not tied to or otherwise connected with any other shield associated with any other center conductor of the multi-conductor cable. In one embodiment, the independently shielded conductor cable is a coaxial cable. The plurality of coaxial cables includes respective centrally located conductors substantially surrounded by corresponding shields. This configuration has significant inherent characteristic capacitance which is typically more easily detected than would be possible in the case of a ribbon or other non- coaxial cable. However, any type of independently shielded conductor cable having a known characteristic capacitance may be used by the cable detection system.

The plurality of independently shielded conductor cables may be contained with a sheath 101a. The sheath 101a terminates at a first end of the cable 100a with a cable connector 102a (e.g. plug). The connector 102a serves as the termination point for the multi- conductor cable 100a. The connector 102a includes pins 104a, 106a, 108a, 110a, 112a and 114a, collectively referred to using reference numeral 103a. Each of the independently shielded conductors within the cable 100a separate within the connector 102a and the center conductor of each terminates at individual pins 104a, 106a, 108a, 110a, 112a and 114a. Each pin is surrounded by a shield 116a. The shield 116a of each pin 103 connects to the shield of the respective independently shielded conductor of the cable 100a. Shield 116a may also be called shield pin 116a due to the fact that part of the shield is exposed for contact connection to monitoring device.

In one embodiment, at an end of the cable opposite the connector 102a, at least one sensor (not shown) is connected to respective independently shielded conductors of the multi- conductor cable 100a and is able to sense data from an object to which the at least one sensor is connected. The sensed data may be communicated along the respective independently shielded conductors for receipt by an electronic device such as a patient monitoring device. Additionally, the cable 100a may selectively receive and communicate multiple power, control and data signals, for example, from an electronic device such as a patient monitor. In this embodiment, the cable 100a represents a six lead sensor cable. The cable 100a includes six independently shielded conductors each terminating at a respective pin 104a, 106a, 108a, 110a, 112a and 114a thereby enabling the electronic device to receive data from each of the six independently shielded conductors via their respective pins 104a, 106a, 108a, 110a, 112a and 114a. One example of this embodiment is cable 100a being a six-lead ECG cable and the electronic device being an ECG monitoring device. In this example the respective pins 104a, 106a, 108a, 110a, 112a and 114a and, by nature of being connected thereto, each independently shielded conductor cable is associated with a respective lead of a typical ECG configuration. In the case of a six lead ECG cable, the pins 103 respectively communicate data sensed from electrodes positioned at various points on a patient' s body such as the left arm (LA) (pin 104a); left leg (LL) (pin 106a), right arm (RA) (pin 108a), right leg (RL) (pin 112a), a first chest lead (V2) (pin 110a) and a second chest lead (V5) (pin 114a).

In another embodiment, cable 100a may be an intermediate cable that functions as an extension cable. The intermediate cable, instead of having sensors at the end opposite the connector 102a, has a second connector. The second connector is substantially similar to the connector 102a with the notable exception of the pins 103. Instead of having pins 103 extending therefrom, the second connector includes a plurality of pin receptacles that selectively receive pins 103 from a connector 102 of a sensor cable such as the 6 lead ECG sensor cable discussed above. The intermediate cable advantageously enables the clinician to employ a greater distance between the patient and the patient monitoring device.

Figure IB is another multi-conductor cable 100b that is used with the cable detection system according to invention principles. The cable 100b shown in Figure IB is substantially similar to the cable 100a of Figure 1A. The cable 100b includes a plurality of independently shielded conductor cables contained within a sheath 101b. The sheath 101b terminates at a first end of the cable 100b with a cable connector 102b (e.g. plug). The connector 102b includes pins 104b, 106b, 108b, 110b, 112b and 114b, collectively referred to using reference numeral 103b. Each of the independently shielded conductors within the cable 100b separate within the connector 102b and the center conductor of each terminates at individual pins 104b, 106b, 108b, 110b, 112b and 114b. Each pin is surrounded by a shield 116b.

However, cable 100b differs from cable 100a in Figure 1A in that not all of the conductors in cable 100b are used to actively communicate data. Instead, only five of the six pins extending from connector 102b are able to communicate data sensed by sensors connected to an object at an end of the cable opposite the connector 102b because a respective one of the pins does not have a center conductor coupled there. Thus, while the pin is present on the connector 102b, there is no center conductor and independent shield connected to the pin that does not communicate data. In order to provide the electronic device to which cable 102b is connected with information identifying that one of the six pins is inactive, the cable 102b has one pin (shown herein as pin 114b) connected via connection 118 to its respective shield 116. This indicates that no center conductor presently connects pin 114b to an electrode at an opposite end there. The connection 118 between the center conductor (pin 114b) with the shield, results in a short circuit on that pin which may be used by the electronic device to identify the type of cable. By detecting a short circuit on pin 114b, the electronic device may understand that only five of the six independently shielded conductors are active thus identifying cable 100b as a five-conductor cable.

Continuing with the embodiment discussed above where the electronic device to which the cable 100b is connected is a patient monitoring device and, more specifically, an ECG monitoring device, cable 100b may be a five (5) lead ECG cable. In this embodiment, five sensors are each coupled to five of the six independently shielded conductors and is able to communicate data sensed by the sensors to the ECG monitoring device in order to derive ECG data for the patient. In the 5 lead ECG cable configuration, the pins 103 respectively communicate data sensed from electrodes positioned at various points on a patient's body such as the left arm (LA) (pin 104b); left leg (LL) (pin 106b), right arm (RA) (pin 108b), right leg (RL) (pin 112b) and a first chest lead (V2) (pin 110a). The connection 118 between the pin 114b and its respective shield 116 resulting in the short circuit and indicates that no central conductor is connected to pin 114b is detectable by the ECG monitoring device and used by the ECG monitoring device to automatically detect that the type of cable connected thereto is a five lead ECG cable. The manner in which this short circuit is detected and used to identify the type of cable will be discussed in greater detail hereinafter with respect to Figures 4 - 7.

Cable 100b being described above as a sensor cable having sensors connected to the end opposite the connector 102b is done so for purposes of example only. In other embodiments, cable 100b may also be an intermediate cable that has one of the independently shielded conductors that does not have a central conductor connected thereto short circuited. However, it is desirable for intermediate cables to be similar to those described in Figure 1A so that the intermediate cable can be used with any type of sensor cable whether it has six active conductors as in Figure 1A, five active conductors as in Figure IB or three active conductors as will be discussed with respect to Figure 1C.

Figure 1C is another multi-conductor cable 100c that is used with the cable detection system according to invention principles. The cable 100c shown in Figure 1C is substantially similar to the cables 100a and 100b of Figures 1A and IB, respectively. The cable 100c includes a plurality of independently shielded conductor cables contained within a sheath 101c. The sheath 101c terminates at a first end of the cable 100c with a cable connector 102c (e.g. plug). The connector 102c includes pins 104c, 106c, 108c, 110c, 112c and 114c, collectively referred to using reference numeral 103c. Each of the independently shielded conductors within the cable 100c separates within the connector 102c and the center conductor of each terminates at individual pins 104c, 106c, 108c, 110c, 112c and 114c. Each pin is surrounded by a shield 116c.

Cable 100c differs from cable 100b in Figure IB and cable 100a in Figure 1A in that only three of the conductors in cable 100c are used to actively communicate data. The three inactive pins and associated shield do not have center conductors connected to the sensor side. In order to provide the electronic device to which cable 102c is connected with information identifying that three of the six pins are inactive, the cable 102c has three pins (shown herein as pins 110c, 112c and 114c) connected via respective connections 118 to respective shields 116. The connections 118 between the center conductors of pins 110c, 112c and 114c with respective shields 116, results in a short circuit on those pins. The short circuit condition may be used by the electronic device to identify the type of cable. By detecting short circuits on pins 110c, 112c and 114c, the electronic device may understand that three of the six independently shielded conductors are active thus identifying cable 100c as a three-conductor cable.

Continuing with the embodiment discussed above where the electronic device to which the cable 100c is connected is a patient monitoring device and, more specifically, an ECG monitoring device, cable 100c may be a three (3) lead ECG cable. In this embodiment, a sensor is coupled each of the three of the six independently shielded conductors and are able to communicate data sensed by the sensors to the ECG monitoring device in order to derive ECG data for the patient. In the three lead ECG cable configuration, the pins 103 respectively communicate data sensed from electrodes positioned at various points on a patient's body such as the left arm (LA) (pin 104c); left leg (LL) (pin 106c) and right arm

(RA) (pin 108c). The connections 118 between the pins 110c, 112c and 114c and their respective shield 116 results in the short circuit and indicates that no central conductor is connected to pins 110c, 112c and 114c is detectable by the ECG monitoring device and used by the ECG monitoring device to automatically detect that the type of cable connected thereto is a three lead ECG cable. The manner in which this short circuit is detected and used to identify the type of cable will be discussed in greater detail hereinafter with respect to Figures 4 - 7.

Exemplary wiring diagrams that correspond to the three cables 100a, 100b, and 100c are depicted in Figures 2A - 2C, respectively. Figure 2A is a wiring diagram that corresponds to cable 100a in Figure 1A. The wiring diagram of Figure 2A represents a cable that has six active conductors and represents one of (a) a six conductor cable for sensing signals using a plurality of sensors; or (b) a six conductor cable that is an intermediate cable that connects a sensor cable with the patient monitoring device. In the instance that this cable is an intermediate cable, the intermediate cable having six active conductors may be used to connect any of a six lead cable, a five lead cable and a three lead cable and still enable the electronic device to determine the presence and type of cable connected to the intermediate cable. As shown in Figure 2A there are six independently shielded conductor cables 204a, 206a, 208a, 210a, 212a and 214a shown grouped together within the sheath 101. The independently shielded conductor cables 204a, 206a, 208a, 210a, 212a and 214a terminate at corresponding pins 104a, 106a, 108a, 110a, 112a and 114a of Figure 1A. Each of the six independently shielded conductor cables 204a, 206a, 208a, 210a, 212a and 214a include a central conductor 220 and a shield 222. In this configuration, signals may be communicated along the central conductor 220 and all six independently shielded conductor cables 204a, 206a, 208a, 210a, 212a and 214a are active. In one embodiment, the wiring diagram of Figure 2A may represent one of a six lead ECG cable or an intermediate extension cable that is able to connect any of a three, five or six lead ECG sensor cable to an ECG monitoring device.

The wiring diagram of Figure 2B represents a cable having five active conductors.

The cable 100b of Figure 2B also has six independently shielded conductor cables 204b, 206b, 208b, 210b, 212b and 214b. The independently shielded conductor cables 204b, 206b, 208b, 210b, 212b and 214b terminate at corresponding pins 104b, 106b, 108b, 110b, 112b and 114b of Figure IB. In this embodiment, five of the six independently shielded conductor cables 204b, 206b, 208b, 210b, and 212b include a central conductor 220 and a shield 222.

As this is a five conductor cable, cable 214b does not include a central conductor and the shield 222 of cable 214b is connected via line 218 to the central conductor 220 thereby resulting in a short circuit on the central conductor rendering the conductor inactive and unable to communicate data thereon. This short circuit on the conductor 220 of pin 214b is selectively detectable and used in automatically identifying this cable as a five conductor cable. In one embodiment, where the electronic device is patient monitoring device and, more specifically, an ECG monitoring device, the wiring diagram for the five conductor cable in Figure 2A may be associated with a five-lead ECG cable having five sensors connected to each of the five active conductors 204b, 206b, 208b, 210b and 212b. The ECG monitoring device will selectively detect the short circuit on pin 214b and identify this cable as a five lead ECG cable in the manner discussed below.

The wiring diagram of Figure 2C represents a cable having three active conductors. The cable 100c of Figure 2C also has six independently shielded conductor cables 204c, 206c, 208c, 210c, 212c and 214c. The independently shielded conductor cables 204c, 206c, 208c, 210c, 212c and 214c terminate at corresponding pins 104c, 106c, 108c, 110c, 112c and 114c of Figure 1C. In this embodiment, three of the six independently shielded conductor cables 204c, 206c and 208c include a central conductor 220 and a shield 222. As this is a three conductor cable, cables 210c, 212c and 214c do not include central conductors and the respective shields 222 of cables 210c, 212c and 214c are connected via 218 to the their respective central conductors 220 resulting in a short circuit on the central conductors thereby rendering the conductors inactive and unable to communicate data thereon. This short circuit on the conductors 220 of pins 212c, 212c and 214c are selectively detectable and used in automatically identifying this cable as a three conductor cable. In one embodiment, where the electronic device is patient monitoring device and, more specifically, an ECG monitoring device, the wiring diagram for the three conductor cable in Figure 2C may be associated with a three-lead ECG cable having three sensors connected to each of the three active conductors 204b, 206b and 208b. The ECG monitoring device will selectively detect the short circuit on pins 210cm 212c and 214c and identify this cable as a three lead ECG cable in the manner discussed below.

In summary, for the purpose of identifying the type of multi-conductor cable connected to an electronic device, the individual conductor pins that are not used for communicating data thereon may be short circuited to at least partially enable the cable detection system to identify the number of active conductors in the multi-conductor cable.

An example of an electronic device that may use any of the cables discussed above in

Figures 1A - 1C is shown in Figures 3 A and 3B. In one embodiment, the electronic device is a patient monitoring device 300 that includes at least one sensor 302 positioned at a predetermined location on the body of a patient and used to sense signals representative of patient physiological data. While only a single sensor 302 is shown in Figures 3A and 3B, persons skilled in the art of patient monitoring will understand that the sensor 302 may include a plurality of sensors positioned at various positions on the patient' s body in order to sense physiological signals from the patient. Alternatively, the sensor 302 may include conductors (not shown) which connect to a plurality of sensors which are placed in contact with the skin of a patient. A cable 100 having a connector 102 couples the sensor 302 to the patient monitoring device 300 via a device connector 304 which is adapted to receive the connector 102 of cable 100. The cable 100 having the connector 102 may be any of the cables 100a, 100b and 100c having respective connectors 102a, 102b and 102c shown in Figures 1A - 1C. The patient monitoring device 300 is adapted to make use of any of cable 100a, 100b and/or 100c to properly process the signals transmitted thereon into patient parameter data. The patient monitoring device 300 may include a cable detector unit 306 that can automatically detect the presence of cable 100 and determine whether cable 100 is one of cable 100a, 100b and 100c.

Data collected by the sensor 302 is transferred to a patient monitor 300 via the cable 100. The patient monitoring device 300 may receive and process the data collected by the sensor. The data may then be displayed on a patient monitor user interface (UI) 308. A user interface (UI), as used herein, comprises one or more display images, generated by the display processor under the control of the processor. The UI also includes an executable procedure or executable application. The executable procedure or executable application conditions the display processor to generate signals representing the UI display images. These signals are supplied to a display device which displays the image for viewing by the user. The executable procedure or executable application further receives signals from user input devices, such as a keyboard, mouse, light pen, touch screen or any other means allowing a user to provide data to the processor. The processor, under control of the executable procedure or executable application manipulates the UI display images in response to the signals received from the input devices. In this way, the user interacts with the display image using the input devices, enabling user interaction with the processor or other device. A graphical user interface (GUI) uses graphical display images, as opposed to textual display images, when generating the UI.

Figure 3B is an alternate embodiment of the system shown in Figure 3A. All of the components labeled with the same reference numerals are equivalent to the components described above with respect to Figure 3A and need not be repeated. The system of Figure 3B includes an intermediate cable 320 that connects the cable 100 to the patient monitoring device 300 enabling the patient to be positioned further from the patient monitoring device as needed. The intermediate cable 320 may be multi-conductor cable having six active independently shielded conductors for transferring data thereon. It is important for the intermediate cable to have six active conductors so that the intermediate cable 320 may be used with any of cable 100a having six active conductors, cable 100b having five active conductors and cable 100c having three active conductors. The intermediate cable 320 includes a first female receptor 322 for receiving the connector 102 of cable 100 and a second connector 324 for connecting the intermediate cable 320 with the device connector 304. Once connected, the data collected by the sensors 302 may be communicated via cable 100 and intermediate cable 320 to the patient monitoring device 300 for processing thereby and display on user interface 308. Additionally, despite the intermediate cable having six active conductors, the cable detector 306 may advantageously automatically determine the presence and type of cable 100 that is connected to the patient monitoring device 300.

Figures 4A and 4B represent block diagrams of two embodiments of the patient monitoring device 300 and detail the additional components that form the cable detection unit 306 shown in Figures 3A and 3B. In Figure 4A, the device 300 is shown connected to a patient 302 via a plurality of sensors 404a - 404n through a multi-conductor cable 100. The multi-conductor cable 100 includes a plurality of independently shielded conductor cables 406a - 406n connected to associated respective sensors 404a - 404n. The presence of the plurality of independently shielded cables is shown in Figure 4 as "/n" which indicates that each independently shielded cable may having a signal communicated thereon. Each independently shielded conductor cable 406a - 406n includes a central conductor 408a - 408n that has a shield 410a - 410n substantially surrounding the central conductor 408a - 408n. The device 300 includes a controller 412 for executing a cable detection algorithm that controls the various components of the cable detection unit 414 to sense a presence and type of cable 100 connected to device 300. In one embodiment, the cable detection unit may automatically determine whether the cable 100 connected to device 300 is one of a three lead cable, a five lead cable, or a six lead cable. The cable detection algorithm executed by the controller 412 advantageously measures and determines an AC condition and a DC condition associated with each independently shielded conductor 406a - 406n, hereinafter termed "lead" and, uses the determined AC and DC condition values to identify the type of cable 100 currently connected to the device 300.

A detector unit 414 including an AC detection unit 416 and a DC detection unit 418 is connected to the controller 412. The AC detection unit 416 is controlled to selectively measure data representing an AC value used to determine the AC condition associated with a respective lead whereas the DC detection unit 418 is controlled to selectively measure data representing a DC value used to determine the DC condition of the same respective lead. In order to determine the AC and DC conditions for each lead 406a - 406n, the controller 412 controls an AC multiplexer (MUX) 428 to connect each of leads 406a - 406n to the AC detection unit 416 to determine the AC condition for the particular lead. The controller 412 controls a DC multiplexer (MUX) 430 to connect each of leads 406a - 406n to the DC detection unit 418 to determine the DC condition for the particular lead. While the sequential connection of leads by AC MUX 428 and DC MUX 430 is described as being connected to the AC detection unit 416 first and to the DC detection unit 418 second, this is merely described for purposes of example and the connection order may be reversed. In one embodiment, the controller 412 may selectively control the AC MUX 428 and DC MUX 430 to sequentially connect each lead 406a - 406n to the AC detection unit 416 and DC detection unit 418. In another embodiment, the controller 412 may selectively control the AC MUX 428 and DC MUX 430 to connect each lead 406a - 406n to the AC detection unit 416 and DC detection unit 418, in a predetermined order.

The detector 414 includes an AC output channel 417 for outputting data representing an AC value representing an amplitude dependent characteristic that is measured by the AC detection unit 416. The detector also includes a DC output channel 419 for outputting data representing the DC voltage value measured by the DC detection unit 418. An output multiplexer 422 is connected to each of the output channels 417 and 419 and is controlled by controller 412 to selectively connect one of the output channels 417 or 419 at a given time to a comparator 424.

To determine the AC condition for a particular lead, the controller 412 controls a switch 420 to connect the particular lead 406a - 406n with an AC signal generator 421 which generates an AC input signal on the particular lead 406a- 406n. The AC detection unit measures an AC value representing amplitude dependent characteristic associated with a capacitive coupling between the shield 410 and the central conductor 408 on the particular lead selected by MUX 428 as an input to the AC detection unit 416. The controller 412 also causes the output multiplexer 422 to connect to the AC output channel 417 with the comparator 424 and provide the measured AC value thereto. The comparator 424 compares the measured AC value to a first AC threshold and a second AC threshold, the first AC threshold having a value lower than the second AC threshold. The comparator 424 determines whether the measured AC value associated with the particular lead is representative of one of (a) a first AC condition when the amplitude dependent characteristic is less than or equal to the first AC threshold; (b) a second AC condition when the amplitude dependent characteristic is greater than the second AC threshold; and (c) a third AC condition when the amplitude dependent characteristic has a value that is greater than the first AC threshold but less than or equal to the second threshold. The AC condition associated with the particular lead 406a - 406n determined by the comparator 424 is stored in memory 426.

Upon determining the AC condition for the particular lead 406a - 406n, the controller 412 controls the DC detection unit 418 to measure a voltage on the particular lead 406a - 406n which is selected as an input to the DC detection unit 418 by DC MUX 430. The controller 412 controls the switch 420 to couple the respective lead 406a - 406n being measured to ground 423 and controls the output multiplexer 422 to connect the comparator 424 with the DC output channel 419. The DC detection unit 418 uses a component 431 to pull the lead being measured to the negative rail and measure the voltage on the selected lead selected by the DC MUX 430. The component 431 provides a weak DC path to the power rail. In one embodiment, as shown herein, the component 431 is a pull down resistor. In another embodiment, the component may be a current source wherein the current flows directionally towards the negative rail. The measured DC voltage value is compared with a DC threshold voltage to determine the DC condition associated with the particular lead 406a - 406n being measured. The DC condition may be one of (a) a first DC condition wherein the measured DC voltage value is greater than the DC threshold voltage or (b) a second DC condition wherein the measured DC voltage value is less than or equal to the DC threshold voltage. The DC condition associated with the particular lead 406a - 406n determined by the comparator 424 is stored in memory 426.

As discussed above, Figure 4A depicts a single switch 420 that is selectively controllable by the controller 412 and can be configured to couple each independently shielded conductor to one of the AC signal generator 421 or ground 423. However, this is shown for purposes of example only and to illustrate the functional operation of the system. In another embodiment, the switch 420 may include a plurality of individual controllable switches 420a - 420n wherein the number of switches 420n corresponds to the number of cables 406n. In this embodiment, each switch may be individually controlled by controller 412 to connect either the conductor 408 or the shield 410 to one of the AC signal generator

421 or ground 423. Moreover, the switch 420 may be one of a mechanical switch or an electronic switch and any description herein regarding movement between operational positions should now be construed as limited to a mechanical movement and instead may be readily understood to encompass any manner of switching. The controller 412 uses the stored AC condition data and DC condition data to determine a lead condition for the particular lead measured. The AC condition data and DC condition data enable the controller 412 to determine if the lead is one of (a) not present; (b) present and not connected to a patient; (c) present and connected to a patient and (d) short circuited. The controller 412 updates a data structure with the determined lead condition value and repeats the above process for each other lead 406a - 406n that has not yet been measured. Once the controller 412 has determined lead condition data for all leads 406a - 406n, the controller may identify the type of cable 100 that is presently connected to the patient monitoring device resulting in the patient monitoring device properly processing the signals sensed by sensors 404a - 404n to derive patient parameter data associated therewith.

An alternate embodiment of the cable detection system is shown in Figure 4B. Figure 4B includes many of the same components as those described in Figure 4A and similarly labeled components operate in a like manner. The embodiment in Figure 4B differs from the embodiment shown in Figure 4A in the following manner. Specifically, the cable detection system of Figure 4B includes an analog-to-digital converter (ADC) 432 coupled to the output of the output multiplexer 422. The ADC 432 receives an analog data representing one of (a) the AC condition from the AC detection unit 416 when the controller 412 controls the output multiplexer 422 to couple the AC output 417 with the ADC 432 or (b) the DC condition from the DC detection unit 418 when the controller 412 controls the output multiplexer 422 to couple the DC output 419 with the ADC 432. The ADC 432 outputs a digital value corresponding to either the AC condition or DC condition and provides the digital value to the comparator 424 which is coupled to the controller 412. The comparator 424 may execute a comparison algorithm for evaluating the condition of the lead based on the output digital value as will be discussed below in Figure 5.

The operation of the cable detection system according to invention principles will now be described with respect to the circuit diagram shown in Figure 5. The circuit diagram of Figure 5 is a simplified electrical circuit that shows the interconnection between the AC detection unit 416 and DC detection unit 418 and a single lead connected to a patient. However, this is shown for purposes of example only and similar electrical circuits may be completed with any number of leads of the multi-conductor cable. The following exemplary description represents the connection of lead 406a having center conductor 408a and shield 410a substantially surrounding central conductor 408a. However, substantially the same circuit and interconnections may be made with any of the independently shielded conductor cables 406b - 406n shown in Figure 4. The following operation takes into account two connection possibilities, one where the sensor 404a is connected to the patient who is grounded virtually through a connection with the patient monitoring device (e.g. a neutral drive lead in an ECG monitoring device) and the other instance where the sensor is not connected to the patient. The cable detection algorithm employed by the controller 412 to detect the AC and DC conditions of the lead 406a are the same no matter the connection state of the sensor. The only difference between the connection states is the resulting intensity of the amplitude dependent characteristic measured by the AC detection unit 416 and the DC voltage measured by the DC detection unit 418.

Initially we turn to the measurement of the amplitude dependent characteristic based on injection of AC current into one of the conductor 408a or shield 410a of lead 406a. The controller 412 controls switch 420 to connect the shield 410 of lead 406 with an AC signal generator 421. The AC signal generator 421 generates an input AC signal which is provided on the shield 410 of the lead 406a. Because there is capacitive coupling between the shield 410a and the central conductor 408a, the AC detection unit 416 measures the amplitude dependent characteristic derived from the capacitive coupling therebetween. The amplitude dependent characteristic of the detected AC output signal may comprise a detected voltage substantially proportional to: (a) a peak to peak amplitude; (b) a root-mean- square amplitude; and/or (c) an average rectified amplitude value, of the detected AC output signal.

One exemplary manner in which the amplitude dependent characteristic may be measured by AC detection unit 416 is as follows. The source 421 of an input electrical AC signal is coupled to the shield 410 of lead 406a. The AC detection unit 416 is coupled to the central conductor 408 of lead 406a. The AC detection unit 416 detects an electrical AC output signal derived by capacitive coupling of the input electrical AC signal applied to the shield 410 occurring within the multi-conductor cable 100. In one embodiment, the multi- conductor cable is formed from a plurality of coaxial cables and lead 406a is a respective one of the plurality of coaxial cables. Additionally, while the algorithm and circuit described in Figure 5 show injecting the AC input signal on the shield 410 and measuring the output derived from the capacitive coupling on the central conductor, this is described for purposes of example only and the input and outputs may be reversed. Alternatively, the input AC signal may be applied to one lead 406a and the output measured at a different lead 402b, for example.

In operation, the shield 410a and the central conductor 408a are capacitively coupled, as represented by a capacitor in phantom between the shield 410a and central conductor 408a. This capacitance provides a path through which the AC input signal received from the AC signal generator 421, may pass from the shield 410a to the central conductor 408a. If the cable 100 is connected, then the input AC signal from the AC signal generator 421 is capacitively coupled from the shield 410a to the central conductor 408a. The output AC signal in the central conductor 408a is detected by the AC detection unit 416. The AC detection unit 416 detects the amplitude of the received output AC signal from the central conductor 408a. The detected amplitude is provided through the analog multiplexer 422 which has been controlled by controller 412 to connect the AC output channel 417 to an analog-to-digital converter (ADC) 501 that automatically converts the analog voltage measurement measured by the AC detection unit 416 into a digital data sample representing the measured AC value. The digital AC value is provided to the digital comparator 424 which compares the measured digital AC value representing the amplitude dependent characteristic to the first and second AC thresholds to determine an AC condition associated with the lead 406a. The inclusion of an ADC 501 is described for purposes of example only and the comparator 424 may be directly connected to the AC output channel 417 via the multiplexer 422. This is one example of how an AC input signal may be used and measured to determine an AC condition associated with the particular lead being measured. Other embodiments and schemes for measuring amplitude dependent characteristic derived from capacitive coupling between the shield 410 and central conductor 408 of lead 406a may be found in US Patent No. 7,902,810 which commonly owned by the present applicant and is incorporated herein in its entirety.

Once the AC condition for lead 406a has been determined, the controller 412 controls the switch 420 to connect the shield 410a to ground for normal operation, then start to measure the DC voltage through DC detection unit 418 on the lead which is pulled down to the lowest possible voltage for the system (e.g. negative rail) through component 502. As shown herein, the component 502 is a resistor having a resistance ranging substantially between 15 mega ohms and 20 mega ohms. Thus, the resistance of component 502 may be weak enough so as not to cause much leakage and offset, but strong enough to withstand noise disturbance. In another embodiment, the component 502 may be a current source, which works essentially the same as a weak pull-down/up resistor. For example, the use of a current source may behave like a resistor with a large resistance, e.g., 5 M ohm to 50 M ohm, in the following manner. If the current source which is sourcing luA has one end tied to 5V power rail and the other end is tied to ground, then the DC reading would be 0V. However, if the current source is tied to 100K ohm resistor, then to ground, the reading would be 0.1V. If it is open, or 100 M ohm above, the current source would be saturated, and the reading would be 5V. Thus, the behavior is analogous to a large resistor with one end pulled up to 5V. By the same scheme, a current source can also sink current to negative rail, thus behaving like a pull-down resistor. Amplifier 504 is coupled to the lead which is pulled down through component 502 and measures the voltage on the lead. The measured voltage is provided, via the DC output channel 419, to the multiplexer 422. The multiplexer 422 is conditioned to connect the DC output channel 419 to the ADC 501 which converts the analog voltage measured by amplifier 504 into a digital DC value. The digital DC value representing the voltage of the lead is provided to the comparator 424 which compares the digital DC voltage value to the DC threshold voltage value to determine if the measured DC voltage exceeds the threshold and assign a DC condition to lead 406a. The inclusion of the ADC 501 to convert the measured DC voltage value from analog to digital is also not required and the comparator can make use of the analog DC voltage value measured by amplifier 504 to determine the DC condition associated with the lead.

The determined AC condition and DC condition associated with lead 406a is stored in memory (426 in Figure 4) and the controller 412 determines the lead condition data for the lead 406a. The lead condition data associated with lead 406a may include one of (a) "lead on" indicating the lead is connected to patient; (b) "lead off indicating that the lead is not connected to patient but the lead and lead wire is available for connection; (c) "no lead wire" indicating that no wire (e.g. center conductor) is connected to lead pins, both center conductor pin and shield pin; and (d) "lead shorted" indicating that lead conductor is shorted to lead shield. Both (a) and (b) can be regarded as normal lead condition whereas (c) and (d) represent a disconnected state.

The controller 412 may determine that lead 406a is in a "normal" condition when the AC current injected onto the shield 410 and read by AC detection circuit 416 results in one of (a) the second AC indicative of the measured amplitude dependent characteristic is greater than the second AC threshold when the electrode is not connected to the patient (see Table 1 below); or (b) the third AC condition indicative of the measured amplitude dependent characteristic being less than or equal to the second AC threshold and greater than the first AC threshold when the electrode is connected to the patient (see Table 1 below).

Determination of a normal condition is also dependent on the DC being pulled to the negative rail by resistor 502 resulting in the DC detection unit 418 determining that the DC value is one of (a) a negative full scale indicating that the voltage is at the lowest possible voltage for the system when the electrode is not connected to the patient; or (b) substantially zero value when the electrode is connected to the patient. The substantially zero value results from the patient being driven to ground by the patient monitoring device (e.g. through neutral drive lead).

The controller 412 may determine that lead 406a is in a "disconnected" condition when the AC current injected onto the shield 410 and read by the AC detection circuit 416 results in measured amplitude dependent characteristic of the AC output signal being in a first AC condition indicating that it has a value lower than the first AC threshold (see Table 1 below). This holds true whether or not the electrode of the lead is connected to the patient. To determine if the lead 406a is in the "disconnected" condition, when the center conductor 408 is pulled to the negative rail by pull down resistor 502, the resulting measured DC voltage value is "negative full scale" (e.g. lowest possible voltage) whether or not the electrode is connected to the patient.

The controller 412 may determine that lead 406a is in a "short circuited" condition when the AC current injected onto the shield 410 and read by the AC detection circuit 416 results in measured amplitude dependent characteristic of the AC output signal being in a second AC condition indicating that it has a value higher than the second AC threshold. This holds true whether or not the electrode of the lead is connected to the patient. To determine if the lead 406a is in the "shorted" condition, when the center conductor 408 is pulled to the ground 423 through switch 420, the resulting measured DC voltage value is substantially "zero" whether or not the electrode is connected to the patient.

The above possible lead conditions associated with respective leads may be summarized in Table 1 entitled "Lead Detection Table".

Case Detected

DC Measurement AC Measurement Comments ID Lead Status

Neither center

Negative Full Scale Low (1^st AC Condition) conductor, nor

1 ( IDC_MEAS_VALI > ( AC_MEAS_VAL< No lead shield exists;

CLB_DTCT_DC_TH ) CLB_DTCT_AC_TH 1 ) no extension cable

Lead exists

Negative Full Scale High (2^nd AC Condition)

with no

2 ( IDC_MEAS_VALI > ( AC_MEAS_VAL> Lead off

patient

CLB_DTCT_DC_TH ) CLB_DTCT_AC_TH2 )

connection

Medium (3^rd AC

~ Zero condition) Lead exists

3 ( IDC_MEAS_VALI < ( CLB_DTCT_ AC_TH 1 with patient Lead on

CLB_DTCT_DC_TH ) <AC_MEAS_VAL< connection

CLB_DTCT_AC_TH2 )

~ Zero High (2^nd AC Condition)

Lead Lead type

4 ( IDC_MEAS_VALI < ( AC_MEAS_VAL>

shorted identification CLB_DTCT_DC_TH ) CLB_DTCT_AC_TH2 )

Table 1 : Lead Condition Table

Table 1 uses the following short hand which corresponds to the above discussed measurements made by the cable detection system. As used in this table "DC_MEAS_VAL" represents the DC voltage value measured by amplifier 504 that represents the voltage on the lead center conductor 408a and "CLB_DTCT_DC_TH" represents the DC threshold value to which "DC_MEAS_VAL" is compared to determine the DC condition for the particular lead. Furthermore, "AC_MEAS_VAL" represents the value of the amplitude dependent characteristic measured by AC detection circuit 416 derived from the capacitive coupling between the central conductor 408 and shield 410. Additionally, "CLB_DTCT_AC_TH1" and "CLB_DTCT_AC_TH2" represent the first and second AC thresholds, respectively. Thus, based on the above table, the controller 412 automatically determines that the lead being measured is in a first lead condition indicating a disconnected state when the magnitude of the measured DC voltage value measured by the DC detection unit 418 is greater than the DC threshold voltage value and that the amplitude dependent characteristic (e.g. voltage) measured by the AC detection unit 416 is less than or equal to the first AC threshold voltage value (e.g. first AC condition). The first lead condition indicates that none of the center conductor, shield or extension cable is present. The controller 412 automatically determines that the lead being measured is in a second lead condition indicating that the lead is present but is in a "lead off state (e.g. not connected to the patient) when the magnitude of the measured DC voltage value measured by the DC detection unit 418 is greater than the DC threshold voltage value and that the amplitude dependent characteristic (e.g. voltage) measured by the AC detection unit 416 is greater than the second AC threshold voltage value (e.g. the second AC condition). The second lead condition is a subset of the "normal" condition discussed above. The controller 412 automatically determines that the lead being measured is in a third lead condition indicating that the lead is present but is in a "lead on" state (e.g. connected to the patient) when the magnitude of the DC voltage value measured by the DC detection unit 418 is less than or equal to the DC threshold voltage value and that the amplitude dependent characteristic (e.g. voltage) measured by the AC detection unit 416 is greater than the first AC threshold voltage value and less than or equal to the second AC threshold voltage (e.g. in the third AC condition). The third lead condition is also subset of the "normal" condition discussed above. The controller 412 automatically determines that the lead being measured is in a fourth lead condition indicating that the lead is short circuited when the magnitude of the DC voltage value measured by the DC detection unit 418 is less than or equal to the DC threshold voltage value and that the amplitude dependent characteristic (e.g. voltage) measured by the AC detection unit 416 is greater than the first AC threshold voltage value.

This cable detection scheme works to automatically identify the type of cable connected to the patient monitoring device when the candidate cable types are of a known configuration each having a predetermined configuration of independently shielded conductors that are in use for a particular candidate cable type. The controller 412 is aware of the candidate cable types (e.g. either 3-lead, 5-lead, 6-lead cable) and the configuration of active versus inactive independently shielded conductors (e.g. which center pins would be short circuited). With this information, the controller 412 selectively determines the lead condition for at least one of the independently shielded conductors known to be inactive may only be either one of the 3-lead or 5-lead cable. By looking to the lead condition on a lead that is known to be inactive for at least two cable types (e.g. 3-Lead and 5-lead), the controller 412 may use the identified lead condition for the lead to quickly identify the type of cable. Referring back the cables in Figures 1A - 1C, pin 116 is short circuited in both the three and five conductor cables. Thus, the controller 412 determines the lead condition for the independently shielded connecter tied to pin 114. If the controller determines that pin 114 is in any lead condition other than lead condition four, the controller detects the cable as one of a six conductor sensor cable or a six conductor intermediate cable. If the controller determines that pin 114 is lead condition four, the controller 412 looks to a second independently shielded conductor also known to be inactive in one of the candidate cable types. For example, the independently shielded conductor that terminates at pin 110 may be known to be inactive in one of the candidate cable types such as a three conductor cable. If the controller determines that pin 110 is in lead condition four and pin 114 is in lead condition four, the controller 412 automatically detects the cable as a three conductor cable. However, if the controller determines that pin 110 is in lead condition two or lead condition three, then the controller 412 detects the cable as a five conductor cable.

Using the AC and DC measurement values as discussed above advantageously enables the controller to properly detect the presence and type of cable connected to the patient monitoring device even when the cable is coupled to the patient monitoring device by an intermediate extension cable. Without using both the AC and DC measurements to obtain AC and DC conditions associated with a particular lead, the controller would not be able to detect the type of cable if an intermediate cable was present due to the capacitive coupling present on all independently shielded conductors of the intermediate cable.

In one embodiment, the patient monitoring device described in Figures 4 and 5 may be an ECG monitoring device able to have one of a three lead, five lead or six lead ECG cable connected thereto. In this embodiment, the relevant thresholds against which the DC and AC measurements are compared are shown in Table 2 entitled "Thresholds for ECG Monitoring Device". The thresholds in Table 2 are identified using the threshold identifiers described above in Table 1.

Table 2: Thresholds for ECG Monitoring Device

The analog value represents the voltages measured directly via the respective AC detection unit 416 and DC detection unit 418. The digital values are derived by ADC 501 in Figure 5. The manner in which these digital units are derived for each of the AC measurements and DC measurements can be obtained by looking to Table 3 entitled "ADC Conversion Table". The values presented in Table 3 are shown for purposes of example only and may differ depending on the type of ADC used. Correspondence between input re-fered AC/DC roeasuremerfi voitages and ADC readings

Table 3: ADC Conversion Table

As can be seen from Table 3, there is a linear relationship between the reference voltages for the ADC and the Digital ADC units shown in columns 1 and 2 of Table 3. By comparing the measured AC and DC values to the respective thresholds and based on the truth table shown in Table 1, the ECG monitoring device is able to automatically detect the presence and type of cable connected thereto. An exemplary algorithm implemented by the controller 412 of an ECG monitoring device that may be used to detect the presence and type of cable connected thereto is depicted in Figure 6. The controller 412 of the ECG monitor has a predetermined number of known candidate cable types that may be connected thereto. Each cable type has a known configuration of active verses inactive conductors associated therewith and which terminate at respective pins (103 in Figures 1A - 1C) on a cable connector (102 in Figures 1A - 1C). The candidate cable types include a six lead ECG cable having six active conductors; a five lead ECG cable having five active conductors and a sixth pin shorted to its respective shield; and a three lead ECG cable having three active conductors and three pins shorted to their respective shields wherein the three lead and five lead cable have one common pin that is shorted to its shield.

The cable detection and identification algorithm starts at box 600 in Figure 6. In block

602, the controller measures the AC value and DC value associated with the pin known to be shorted (e.g. V5 lead) in both the three lead and five lead ECG cables. The AC and DC values are measured as discussed above and the AC and DC conditions for the V5 lead are used to determine lead condition data in accordance with Table 1. The result of the measurement in block 602 produces four candidate lead conditions to be associated with the V5 lead. If the result in box 604a of the measurement in block 602 identifies V5 as being lead condition 1 (Case 1 in Table 1), then V5 is determined not to exist. If the result in box 604b of the measurement in block 602 identifies V5 as being lead condition 2 (Case 2 in Table 1), then V5 is determined not to be present but not connected to the patient (e.g. Lead-Off). If the result in box 604c of the measurement in block 602 identifies V5 as being lead condition 3 (Case 3 in Table 1), then V5 is determined to be present and connected to the patient (e.g. Lead-on). If the result in box 604d of the measurement in block 602 identifies V5 as being lead condition 4 (Case 4 in Table 1), then V5 is determined to be short circuited. The controller 412 stores the lead condition data of boxes 604a - 604d in memory

The controller then measures, in block 606, the AC value and DC value associated with a second pin known to be shorted (e.g. RL lead) in the three lead cable but not in the five lead ECG cable. The AC and DC values are measured as discussed above and the AC and DC conditions for the RL lead are used to determine lead condition data in accordance with Table 1. The result of the measurement in block 606 produces four candidate lead conditions to be associated with the RL lead. The candidate lead conditions are listed in boxes 608a - 608d and represent the same lead conditions as those described in boxes 604a - 604d. The controller 412 stores the lead condition data of boxes 608a - 608d in memory.

In block 610, the controller measures the AC value and DC value associated with a third pin that is known to be active in all three candidate cable types (e.g. RA lead being active in the six lead, five lead and three lead cable). The AC and DC values are measured, in block 610, as discussed above and the AC and DC conditions for the RA lead are used to determine lead condition data in accordance with Table 1. The result of the measurement in block 610 produces four candidate lead conditions to be associated with the RA lead. The candidate lead conditions are listed in boxes 612a - 612d and represent the same lead conditions as those described in boxes 604a - 604d. The controller 412 stores the lead condition data of boxes 608a - 608d in memory.

The controller 412 then uses the lead condition data for each of the V5, RL and RA leads to determine the type of cable currently connected to the ECG monitor. In box 614, the controller queries whether or not the lead condition data for V5, RL and RA were all determined to be lead condition 1. If the result of the query in box 614 is true, then the controller determines that the cable is unplugged as shown in box 615. If the result of the query in box 614 is false, the controller queries, in box 616, whether or not the lead condition data for V5, RL and RA were all determined to be lead condition 2 or lead condition 3. If the result of the query in box 616 is true, the controller detects that the cable is present and identifies the cable as being a six lead cable as shown in box 617. If the result of the query in box 616 is false, the controller queries, in box 618, if the V5 lead is in lead condition 4 and RL and RA are in lead condition 2 or lead condition 3. If the result of the query in box 618 is true, the controller detects that the cable is present and identifies the cable as being a five lead cable as shown in box 619. If the result of the query in box 618 is false, the controller queries, in box 620, if the V5 lead and RL lead is in lead condition 4 and the RA lead is in lead condition 2 or lead condition 3. If the result of the query in box 620 are true, the controller detects that the cable is present and identifies the cable as being a three lead cable as shown in box 621. If the query in box 620 is false, the controller will be unable to detect the presence of the cable or identify the type of cable that it might be as shown in box 623.

By detecting the short circuit condition in respective leads, the cable detection scheme for the ECG monitor advantageously identifies the presence and type of cable connected thereto even when an intermediate cable having six active conductors each having their own capacitive coupling associated therewith is used to connect the electrodes on the patient to the ECG monitoring device. This cable detection scheme also works with existing cable type that do not have unused leads shorted to their respective shields and which are not connected using an intermediate cable.

Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments of the invention which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention. This disclosure is intended to cover any adaptations or variations of the embodiments discussed herein.

Claims

What is claimed is:

1. A cable detection system for detecting a type of cable connected to a patient monitoring device, comprising:

an AC signal generator that generates an input electrical AC signal;

a switch that selectively connects a first lead of the cable with one of (a) the AC signal generator; or (b) ground;

a component coupled to a second lead of the cable;

a detector coupled to the second lead of the cable that detects an AC output signal and a DC signal on the second lead; and

a controller that controls the switch to operate in a first position coupling the AC signal generator with the first lead enabling the detector to measure the AC output signal and determine an AC condition associated with the cable and a second position coupling the first lead to ground and enabling the detector to measure the DC signal and determine a DC condition associated with the cable, the controller using the determined AC condition and DC condition associated with the cable to identify the type of cable connected to the patient monitoring device.

2. The cable detection system according to claim 1, wherein

the component is one of (a) a resistor or (b) a current source.

3. The cable detection system according to claim 1, wherein

the controller determines the AC condition by measuring the AC output signal derived by a capacitive coupling between the first lead and second lead and comparing an amplitude dependent characteristic of the AC output signal with both of a first AC threshold and a second AC threshold, the first AC threshold being less than the second AC threshold.

4. The cable detection system according to claim 3, wherein

the amplitude dependent characteristic is a voltage derived from the capacitive coupling between the first lead and the second lead and the first AC threshold is a first voltage and the second AC threshold is a second voltage greater than the first voltage.

5. The cable detection system according to claim 3, wherein

the controller determines the AC condition associated with the cable is one of (a) a first AC condition when the amplitude dependent characteristic has a value less than or equal to the first AC threshold; (b) a second AC condition when the amplitude dependent characteristic has a value greater than the second AC threshold; and (c) a third AC condition when the amplitude dependent characteristic has a value greater than the first AC threshold but less than or equal to the second threshold.

6. The cable detection system according to claim 1, wherein

the DC output signal measured by the detector represents a voltage measured on the selected lead which is pulled-down through the component.

7. The cable detection system according to claim 6, wherein

the controller determines the DC condition associated with the cable is one of (a) a first DC condition when the measured DC signal has a value greater than the DC threshold or (b) a second DC condition when the measured DC signal has a value less than or equal to the DC threshold.

8. The cable detection system according to claim 1 wherein

the controller determines a lead condition associated with the cable using the determined AC condition and DC condition, the lead condition being one of (a) disconnected; (b) lead-off; (c) lead-on; or (d) short circuited.

9. The cable detection system according to claim 8, wherein

the controller determines the cable is a first type of cable in response to the lead condition being short circuited and a second type of cable in response to the lead condition being any of lead-off or lead-on.

10. The cable detection system according to claim 9, further comprising a memory for storing data representing at least one of the (a) AC condition; (b) DC condition; (c) the lead condition; and (d) cable type.

11. The cable detection system according to claim 1, wherein

the patient monitoring device is an ECG monitor and the type of cable is at least one of (a) a 5-lead ECG cable; (b) a 3-lead ECG cable; (c) a 6-lead ECG cable and (d) an extension cable for connecting any of (a), (b) or (c) with the ECG monitoring device.

12. The cable detection system according to claim 1, wherein

the cable is a multi conductor cable including a plurality of independently shielded conductors, each independently shielded conductor having a first lead and a second lead.

13. The cable detection system according to claim 12, wherein

the controller sequentially controls the switch to operate in the first position and second position to individually couple the first lead of each independently shielded conductor with one of the AC signal generator and ground enabling the detector to measure the AC output signal and DC signal for each independently shielded conductor, the controller determines the AC condition and DC condition associated with each of the independently shielded conductors and uses the AC condition and DC condition of each independently shielded conductor to identify a type of cable connected to the patient monitoring device.

14. The cable detection system according to claim 13, wherein

the controller identifies the cable as one of (a) a first type of cable when the AC condition and DC condition indicate that one of the independently shielded conductors is short circuited; (b) a second type of cable when the AC condition and DC condition indicate that two of independently shielded conductors are short circuited; and (c) a third type of cable when the AC condition and DC condition indicate that none of the independently shielded conductors are short circuited.

15. The cable detection system according to claim 1, wherein

said first lead is a shield of the cable and said second lead is an inner conductor of

16. The cable detection system according to claim 1, wherein

said second lead is a shield of a cable and said first lead is an inner conductor of said cable.

17. The cable detection system according to claim 1, wherein

said amplitude dependent characteristic is proportional to one of, (a) a peak to peak amplitude; (b) a root-mean-square amplitude; and (c) an average rectified value, of said detected AC output signal.

18. A method of detecting a type of cable connected to a patient monitoring device, comprising the activities of:

generating an input electrical AC signal by an AC signal generator;

selectively controlling a switch to operate in one of (a) a first position connecting the

AC signal generator with a first lead and (b) a second position connecting the first lead to ground;

detecting and measuring an AC output signal on a second lead when the switch is in the first position;

determining an AC condition associated with the cable;

detecting and measuring a DC signal through a component coupled to the second lead when the switch is in the second position;

determining a DC condition associated with the cable; and,

using the determined AC condition and DC condition associated with the cable to identify the type of cable connected to the patient monitoring device.

19. The method according to claim 18, wherein the activity of detecting and measuring the DC signal is performed by one of

(a) measuring a voltage on the selected lead which is pulled-down through a resistor; or

(b) applying a current from a current source to the second lead and measuring the DC signal in response thereo.

20. The method according to claim 18, wherein the activity of determining the AC condition further comprises

measuring the AC output signal derived by a capacitive coupling between the first lead and second lead and comparing an amplitude dependent characteristic of the AC output signal with both of a first AC threshold and a second AC threshold, the first AC threshold being less than the second AC threshold.

21. The method according to claim 18, wherein

the amplitude dependent characteristic is a voltage derived from the capacitive coupling between the first lead and the second lead and the first AC threshold hold is a first voltage and the second AC threshold is a second voltage greater than the first voltage.

22. The method according to claim 18, further comprising

determining the AC condition associated with the cable is one of (a) a first AC condition when the amplitude dependent characteristic has a value less than or equal to the first AC threshold; (b) a second AC condition when the amplitude dependent characteristic has a value greater than the second AC threshold; and (c) a third AC condition when the amplitude dependent characteristic has a value greater than the first AC threshold but less than or equal to the second threshold.

23. The method according to claim 18, further comprising

determining the DC condition associated with the cable is one of (a) a first DC condition when the measured DC signal has a value greater than the DC threshold or (b) a second DC condition when the measured DC signal has a value less than or equal to the DC threshold.

24. The method according to claim 18, further comprising

determining a lead condition associated with the cable using the determined AC condition and DC condition, the lead condition being one of (a) disconnected; (b) lead-off; (c) lead-on; or (d) short circuited.

25. The method according to claim 24, further comprising

determining the cable is a first type of cable in response to the lead condition being short circuited and a second type of cable in response to the lead condition being any of lead- off or lead-on.

26. The method according to claim 24, further comprising

storing, in a memory, data representing at least one of the (a) AC condition; (b) DC condition; (c) the lead condition; and (d) cable type.

27. The method according to claim 18, wherein

the cable is a multi conductor cable including a plurality of independently shielded conductor, each independently shielded conductor having a first lead and a second lead and further comprising sequentially controlling the switch to move between the first position and second position to individually couple the first lead of each independently shielded conductor with one of the AC signal generator and ground;

measuring the AC output signal and DC signal for each independently shielded conductor;

determining the AC condition and DC condition associated with each of the of the independently shielded conductors; and

using the AC condition and DC condition of each independently shielded conductor to identify a type of cable connected to the patient monitoring device.

28. The method according to claim 27, further comprising

identifying the cable as one of (a) a first type of cable when the AC condition and DC condition indicate that one of the independently shielded conductors is short circuited; (b) a second type of cable when the AC condition and DC condition indicate that two of independently shielded conductors are short circuited; and (c) a third type of cable when the AC condition and DC condition indicate that none of the independently shielded conductors are short circuited.

29. The method according to claim 16, wherein

the first lead is a shield of the cable and said second lead is an inner conductor of said cable.

30. The method according to claim 16, wherein

31. The method according to claim 2, wherein

said amplitude dependent characteristic is proportional to one of, (a) a peak to peak amplitude; (b) a root-mean-square; and (c) an average rectified value, of said detected AC output signal.

32. The method according to claim 18, wherein

33. A multi-conductor cable comprising

a plurality of independently shielded conductors, each independently-ihielded conductor including a central conductor and a shield substantially surrounding the central conductor;

a plurality of sensors for sensing data from an object, each of the plurality of sensors coupled to respective ones of the plurality of independently shielded conductor;

a connector having a plurality of pins, each of the plurality of independently shielded conductors terminating at a respective one of the plurality of pins, the connector enabling connection of the multi-conductor cable with an electronic device and having at least two independently shielded conductors short circuited

34. The multi-conductor cable according to claim 31 , wherein

The at least two short circuited independently shielded conductors are detectable by the electronic device and used in determining the type of multi-conductor cable.

35. A multi-conductor electrocardiogram (ECG) cable comprising

a plurality of independently shielded conductors, each independently shielded conductor including a central conductor and a shield substantially surrounding the central conductor;

a plurality of electrodes for sensing electrophysiological signals from a patient, each of the plurality of electrodes coupled to respective ones of the plurality of independently shielded conductors;

a connector having a plurality of pins, each of the plurality of independently shielded conductors terminating at a respective one of the plurality of pins, the connector enabling connection of the multi-conductor ECG cable with an electrocardiogram monitoring device and having a respective independently shielded conductor configured to communicate data associated with the V5 lead in an ECG lead configuration short circuited indicating that the multi-conductor ECG cable is a 5 lead ECG cable.

36. The multi-conductor ECG cable according to claim 33, further comprising a respective independently shielded conductor configured to communicate data associated with the RL lead in an ECG lead configuration short circuited indicating that the multi-conductor ECG cable is a 3 lead ECG cable.