Apparatus for obtaining biological information

Abstract

An apparatus for obtaining bio information includes: a first electrode portion including a current electrode and a voltage electrode arranged to contact a first body portion of a subject; a second electrode portion including a current electrode and a voltage electrode arranged to contact a second body portion of the subject; and a measuring unit configured to measure a bio impedance of the subject by applying a current to the current electrodes of the first and second electrode portions and detecting a voltage at the voltage electrodes of the first and second electrode portions. In order to decrease errors of a measured bio impedance, contact resistances of the first and second body portions of the subject contacting the current electrode and the first and second body portions of the subject contacting the voltage electrode are different from each other, for at least one of the first and second electrode portions.

1 . A wearable device comprising
 a first electrode portion comprising two electrodes configured to be electrically isolated from each other and to be in direct contact with a user of the wearable device; and   a second electrode portion comprising two electrodes configured to be electrically isolated from each other and sized and arranged to be simultaneously touchable by a single finger of the user,   wherein, when the first electrode portion and the second electrode portion are touched by the user, the first electrode portion and the second electrode portion form a closed circuit through the user, and   wherein, first electrode of the two electrodes of the second electrode portion surrounds a second electrode of the two electrodes of the second electrode portion.   
     
     
         2 . The wearable device of  claim 1 , wherein, the first electrode of the two electrodes of the second electrode portion has an area different from the second electrode of the two electrodes of the second electrode portion. 
     
     
         3 . The wearable device of  claim 1 , wherein, a first electrode of the two electrodes of the first electrode portion surrounds a second electrode of the two electrodes of the first electrode portion. 
     
     
         4 . The wearable device of  claim 1 , wherein, a first electrode of the two electrodes of the first electrode portion has an area greater than a second electrode of the two electrodes of the first electrode portion. 
     
     
         5 . The wearable device of  claim 1 , wherein the wearable device is a wrist-wearable type and comprises a main body and a strap. 
     
     
         6 . The wearable device of  claim 5 , wherein the first electrode portion is arranged on an inner surface of the main body or an inner surface of the strap so as to contact a wrist of the user, and
 the second electrode portion is arranged on an outer surface of the main body or an outer surface of the strap.   
     
     
         7 . The wearable device of  claim 1 , wherein, the first electrode of the two electrodes of the second electrode portion has circular ring shape and the second electrode of the two electrodes of the second electrode portion has a circular shape. 
     
     
         8 . The wearable device of  claim 1 , wherein, the first electrode of the two electrodes of the second electrode portion has an oval ring shape and the second electrode of the two electrodes of the second electrode portion has an oval shape. 
     
     
         9 . The wearable device of  claim 1 , wherein, the first electrode of the two electrodes of the second electrode portion is a current electrode configured to which current is applied, and the second electrode of the two electrodes of the second electrode portion is a voltage electrode configured from which voltage is detected. 
     
     
         10 . The wearable device of  claim 9 , wherein, the first electrode of the two electrodes of the second electrode portion has circular ring shape and the second electrode of the two electrodes of the second electrode portion has a circular shape, the two electrodes of the second electrode portion satisfying following condition; 
       
         
           
             
               a 
               < 
               
                 
                   
                     - 
                     d 
                   
                   + 
                   
                     
                       
                         2 
                          
                         
                           b 
                           2 
                         
                       
                       - 
                       
                         d 
                         2 
                       
                     
                   
                 
                 2 
               
             
           
         
         where, a is a radius of the circular shape, b is an external radius of the circular ring shape, and d is a distance between the two electrodes of the second electrode portion. 
       
     
     
         11 . The wearable device of  claim 1 , wherein, the first electrode of the two electrodes of the second electrode portion is a voltage electrode configured from which voltage is detected, and the second electrode of the two electrodes of the second electrode portion is a current electrode configured to which current is applied. 
     
     
         12 . The wearable device of  claim 11 , wherein, the first electrode of the two electrodes of the second electrode portion has circular ring shape and the second electrode of the two electrodes of the second electrode portion has a circular shape, the two electrodes of the second electrode portion satisfying following condition; 
       
         
           
             
               a 
               > 
               
                 
                   
                     - 
                     d 
                   
                   + 
                   
                     
                       
                         2 
                          
                         
                           b 
                           2 
                         
                       
                       - 
                       
                         d 
                         2 
                       
                     
                   
                 
                 2 
               
             
           
         
         where, a is a radius of the circular shape, b is an external radius of the circular ring shape, and d is a distance between the two electrodes of the second electrode portion. 
       
     
     
         13 . A wearable device comprising a first electrode portion comprising two electrodes configured to be electrically isolated from each other and to be in direct contact with a user of the wearable device; and
 a second electrode portion comprising two electrodes configured to be electrically isolated from each other and sized and arranged to be simultaneously touchable by a single finger of the user,   wherein, when the first electrode portion and the second electrode portion are touched by the user, the first electrode portion and the second electrode portion form a closed circuit through the user, and   wherein, a first electrode of the two electrodes of the second electrode portion has an area greater than a second electrode of the two electrodes of the second electrode portion.   
     
     
         14 . The wearable device of  claim 13 , wherein, a first electrode of the two electrodes of the first electrode portion has an area different from a second electrode of the two electrodes of the first electrode portion. 
     
     
         15 . The wearable device of  claim 13 , wherein, the first electrode of the two electrodes of the second electrode portion is a current electrode configured to which current is applied and the second electrode of the two electrodes of the second electrode portion is a voltage electrode configured from which voltage is detected. 
     
     
         16 . The wearable device of  claim 13 , wherein the wearable device is a wrist-wearable type and comprises a main body and a strap. 
     
     
         17 . The wearable device of  claim 16 , wherein the first electrode portion is arranged on an inner surface of the main body or an inner surface of the strap so as to contact a wrist of the user, and
 the second electrode portion is arranged on an outer surface of the main body or an outer surface of the strap.   
     
     
         18 . The wearable device of  claim 1 , wherein a first electrode of the two electrodes of the first electrode portion is disposed coplanarly with a second electrode of the two electrodes of the first electrode portion. 
     
     
         19 . The wearable device of  claim 1 , wherein the first electrode of the second electrode portion is concentric with the second electrode of the second electrode portion. 
     
     
         20 . A wearable device comprising:
 a first pair of a first current electrode and a first voltage electrode that are disposed on an internal surface facing a skin at a wrist of a user; and   a second pair of a second current electrode and a second voltage electrode that are disposed on an external surface that is opposite to the internal surface, and are arranged to be simultaneously touchable by a single finger of the user,   wherein the first current electrode and the second current electrode form a first closed circuit, and the second voltage electrode and the second voltage electrode form a second closed circuit, the first closed circuit and the second closed circuit being formed in response to the first pair and the second pair being simultaneously in contact with the skin of the wrist and the single finger, respectively, and   wherein a contact resistance of the first voltage electrode is greater than a contact resistance of the first current electrode, and a contact resistance of the second voltage electrode is greater than a contact resistance of the second current electrode.