Sensor identification method and system

Abstract

An inventive method and system are provided for identifying a compatible photoplethysmographic sensor when interconnected to a given photoplethysmographic monitor. The method and system may further provide for the identification of which of a plurality of compatible sensors is interconnected to allow for selective calibration of the photoplethysmographic monitor. In this regard, the system and method may entail provision of a predetermined drive or test signal to a light source and/or identification element (i.e., sensor elements) of a photoplethysmographic sensor, and the obtainment of a corresponding output signal for use in sensor identification. In one approach, an output signal is obtained from at least one of three sensor elements each of which is interconnected between a different pair of sensor terminals which is a unique combination of two of four sensor terminals on the sensor. In this regard, individual circuits may be formed through each sensor element allowing for enhanced flexibility in signal application.

What is claimed:  
     
         1 . A method using a photoplethysmographic system, comprising: 
 releaseably interconnecting a photoplethysmographic sensor to a photoplethysmographic monitor,    wherein a first pair of terminals on said sensor is connected for receiving first drive signals from said monitor for illuminating a first light source coupled between said first pair of terminals,    wherein a second pair of terminals on said sensor is connected for receiving second drive signals from said monitor for illuminating a second light source coupled between said second pair of terminals,    wherein a third pair of terminals on said sensor is connected for receiving an interrogation signal from said monitor for application across an identification element coupled between said third pair of terminals, and    wherein said first second and third connections each utilize a unique combination of terminals and wherein each said first second and third terminal pairs includes at least one terminal included in another of said first second and third terminal pairs;    applying an interrogation signal across said third pair of terminals to obtain an output signal from said identification element; and    utilizing said output signal to identify said sensor.    
     
     
         2 . The method of  claim 1 , wherein applying step comprises applying an electrical signal to one terminal of said third pair of terminals to obtain said output signal at the other terminal of said third pair of terminals.  
     
     
         3 . The method of  claim 2 , wherein said identification element is a diode.  
     
     
         4 . The method of  claim 3 , wherein said output comprises a minimal and predeterminable voltage drop across said diode.  
     
     
         5 . The method of  claim 3 , wherein said applying step further comprises; 
 applying a first electrical signal to obtain a first output signal from said diode; and    applying a second electrical signal to obtain a second output signal from said diode.    
     
     
         6 . The method of  claim 5 , wherein said first and second electrical signals have different magnitudes.  
     
     
         7 . The method of  claim 6 , wherein said first and second electrical signals have first and second current levels.  
     
     
         8 . The method of  claim 7 , wherein said first and second current level are selected to produce first and second minimal and predeterminable voltage drops across said diode.  
     
     
         9 . The method of  claim 8 , wherein said first and second voltage drops are substantially equal.  
     
     
         10 . The method of  claim 7 , wherein said first and second electrical signals have a positive polarity and a negative polarity, respectively, as applied to said identification element.  
     
     
         11 . The method of  claim 1 , further comprising: 
 upon obtaining said output signal, disabling said third pair of terminals on said sensor.    
     
     
         12 . The method of  claim 1 , further comprising: 
 applying an interrogation signal across at least one of said first and second pairs of terminals to obtain an additional output signal from at least one of said first and second light sources.    
     
     
         13 . The method of  claim 1 , further comprising: 
 establishing a connection with a fourth pair terminals on said sensor operable to complete a circuit monitored by said monitor to identify sensor interconnection.    
     
     
         14 . The method of  claim 13 , further comprising: 
 applying an electrical signal to one terminal of said fourth pair of terminals to obtain an interconnection output signal at the other terminal of said fourth pair of terminals    
     
     
         15 . The method of  claim 14 , further comprising: 
 upon identifying said interconnection output signal, performing said applying step across said third pair of terminals on said sensor.    
     
     
         16 . The method of  claim 14 , wherein said interconnection output signal is utilized procure sensor information.  
     
     
         17 . The method of  claim 1 , upon identifying said sensor, further comprising the step of: 
 applying predetermined drive signals to one terminal of at least one of said first and second terminal pairs on said sensor for controllably illuminating at least one of said first and second light sources.    
     
     
         18 . The method of  claim 17 , wherein said at least one of said first and second light sources illuminates patient tissue-under-test.  
     
     
         19 . The method of  claim 18 , further comprising: 
 establishing a connection with a fifth pair of terminals on said sensor having a light detector coupled there between; and    applying a detector drive signal to one terminal of said fifth pair of terminals to obtain a detector output signal at the other terminal of said third pair of terminals, wherein said detector output signal is indicative of light absorption of said tissue-under-test.    
     
     
         20 . The method of  claim 15 , wherein said detector output signal is utilized for at least one of: 
 determining a blood analyte concentration value; and    determining at least one physiological parameter.    
     
     
         21 . The method of  claim 20 , wherein said blood analyte concentration value comprises a blood oxygen value.  
     
     
         22 . The method of  claim 20 , wherein said physiological parameter comprises a heart rate.  
     
     
         23 . The method of  claim 1 , wherein releaseably interconnecting further comprises: 
 interconnecting each terminal on said sensor to said monitor via a dedicated electrical pathway.    
     
     
         24 . The method of  claim 23 , wherein four dedicated electrical pathways interconnect said first, second and third pairs of terminals on said sensor to said monitor.  
     
     
         25 . The method of  claim 1 , further comprising: 
 comparing said output signal to a predetermined range of values to select information for use in calibrating said monitor.    
     
     
         26 . The method of  claim 25 , wherein when said output signal is outside said predetermined range, said method further comprising at least one of: 
 providing an output to a user indicating that the sensor is not compatible with said monitor; and    disabling said monitor for use with said interconnected sensor.    
     
     
         27 . The method of  claim 25 , wherein when said output signal is within said predetermined range, said method further comprising: 
 utilizing said output signal to select one of a plurality of calibration values for use in photoplethysmographic monitoring.    
     
     
         28 . A photoplethysmographic monitoring system, comprising: 
 a photoplethysmographic sensor including: 
 a first light source interconnected between a first pair of sensor terminals;  
 a second light source interconnected between a second pair of sensor terminals; and  
 an identification element interconnected between a third pair of sensor terminals, wherein each of said pairs of sensor terminals comprises a unique combination of sensor terminals and wherein each said first second and third pairs of sensor terminals includes at least one terminal included in another of said first second and third pairs of sensor terminals;  
   a photoplethysmographic monitor removeably interconnectable to each of said first, second and third pairs of sensor terminals, said monitor operative to selectively apply predetermined signals to a first terminal of each of said pairs of sensor terminals and obtain an output signal at a second terminal of each of said pairs of sensor terminals; and    a processor operatively associated with said monitor operative to utilize at least one said output signal to identify said sensor.    
     
     
         29 . The system of  claim 28 , wherein said first, second and third pairs of terminals each comprise a unique combination of two of four terminals on said sensor.  
     
     
         30 . The system of  claim 29 , wherein said four terminals are removeably interconnected to said monitor via four dedicated electrical pathways.  
     
     
         31 . The system of  claim 28 , wherein said monitor is operative to apply an interrogation signal across said third pair of sensor terminals to obtain an identification output signal from said identification element.  
     
     
         32 . The system of  claim 31 , wherein said identification element comprises a diode.  
     
     
         33 . The system of  claim 32 , wherein said diode produces a minimal and predeterminable voltage drop across said third pair of terminals in response to said interrogation signal.  
     
     
         34 . The system of  claim 31 , wherein said monitor is operative to apply first and second interrogation signals across said third pair of sensor terminals to obtain first and second identification output signals from said identification element.  
     
     
         35 . The system of  claim 34 , wherein said first and second interrogation signals having different magnitudes.  
     
     
         36 . The system of  claim 35 , wherein said first and second interrogation signals have different current levels.  
     
     
         37 . The system of  claim 36 , wherein said identification element is a diode and said first and second output signals comprise first and second minimal and predeterminable voltage drops across said third pair of terminals.  
     
     
         38 . The system of  claim 37 , wherein said diode is selected such that said first and second voltage drops are substantially equal.  
     
     
         39 . The system of  claim 28 , wherein said monitor is operative to apply interrogation signals to at least one of said first and second pairs of sensor terminals to obtain at least one identification output from one of said first and second light sources.  
     
     
         40 . The system of  claim 28 , wherein, upon identifying said sensor, said monitor is operative to deactivate said connection with said third pair of sensor terminals.  
     
     
         41 . The system of  claim 28 , wherein said sensor further comprises: 
 a light detector interconnected between a fourth pair of sensor terminals for detecting light output signals from said first and second light sources and providing a detector output signal indicative thereof.    
     
     
         42 . The system of  claim 42 , wherein said processor is operative to utilize said detector output signal to compute at least one blood analyte concentration value.  
     
     
         43 . The system of  claim 28 , further comprising: 
 a cable interconnecting said sensor to said monitor, wherein said cable provides a dedicated electrical pathway between each said sensor terminal and said monitor.