Patent Publication Number: US-2021169420-A1

Title: Wearable electronic device and method for detecting contact of living body to wearable electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based on and claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2019-0163919, filed on Dec. 10, 2019, in the Korean Intellectual Property Office, the disclosure of which is herein incorporated by reference in its entirety. 
     BACKGROUND 
     Field 
     One or more embodiments disclosed herein generally relate to a wearable electronic device capable of detecting contact of a living body portion thereto using electrodes, and a method for detecting contact of the living body to the wearable electronic device. 
     Description of Related Art 
     As hardware and software technologies develop, electronic devices supporting various functions are introduced into the market. Recently, increased attention has been directed to healthcare, and this has led to increased demand for measurement and management of health conditions of users of electronic devices. Accordingly, markets have emerged for electronic devices equipped with various biometric sensors for measuring health conditions and for providing related services. 
     The biometric sensors may include a blood glucose meter, a blood pressure monitor, a thermometer, a heart rate monitor (HRM), an electrocardiogram (ECG) sensor, a photoplethysmography (PPG) sensor, a fingerprint scanner, an iris scanner, and the like. 
     Among the aforementioned sensors, the ECG sensor may detect a potential difference generated when heart muscle contracts and relaxes via the ECG electrode in contact with the living body skin. The action potential generated by the heartbeat causes a current that spreads from the heart to the whole body, and this current generates a potential difference. The ECG sensor can be used to determine the size of the heartbeat and whether the heart is damaged by detecting the electrical activity of the heart and measuring whether the heartrate is constant. The ECG sensor can be deployed in various applications, such as recognizing the user&#39;s emotional state or performing user authentication using a unique ECG value. 
     Various biometric sensors may be equipped in a wearable electronic device that may be placed on the user. Upon detecting that the device is worn, the wearable electronic device may obtain biometric signals and check the user&#39;s health condition. 
     SUMMARY 
     A wearable electronic device equipped with various biometric sensors may apply current to two electrodes of the device and detect whether the wearable electronic device is worn on the user&#39;s body using the potential between the two electrodes. The method of detecting whether the wearable electronic device is worn on the user&#39;s body using the potential between the two electrodes to which current has been applied changes the potential between the two electrodes and thus limits detection of biometric signals. When alternating current (AC) is applied to the two electrodes, unnecessarily high frequency sampling may be required, or an additional analog circuit for extracting the impedance component, e.g., a demodulator, may be needed. 
     According to certain embodiments, there is provided a wearable electronic device capable of detecting contact of a living body portion thereto using electrodes, and a method for detecting contact of the living body to the wearable electronic device. 
     In accordance with an embodiment, a wearable electronic device comprises at least two electrodes for measuring a biometric signal, a living body contact detecting unit configured to apply a voltage to at least one electrode contacting a living body among the at least two electrodes and output information indicating an operation state for biometric signal measurement of the wearable electronic device based on a voltage output from the at least one electrode, and a processor configured to determine the operation state for biometric signal measurement of the wearable electronic device, based on the information received from the living body contact detecting unit. 
     In accordance with an embodiment, a method for detecting contact of a living body to a wearable electronic device comprises applying a voltage to at least one electrode contacting the living body among at least two electrodes for biometric signal measurement, outputting information indicating an operation state for biometric signal measurement of the wearable electronic device based on another voltage output from the at least one electrode, and determining the operation state of the biometric signal measurement of the wearable electronic device based on the information indicating the operation state of the biometric signal measurement of the wearable electronic device. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant aspects thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1A  is a view illustrating an electronic device in a network environment according to an embodiment; 
         FIG. 1B  is a front perspective view illustrating an electronic device according to an embodiment; 
         FIG. 1C  is a rear perspective view illustrating an electronic device as shown in  FIG. 1B ; 
         FIG. 1D  is an exploded perspective view illustrating an electronic device as shown in  FIG. 1B ; 
         FIG. 2  is a block diagram schematically illustrating a wearable electronic device according to an embodiment; 
         FIG. 3  is a block diagram schematically illustrating a living body contact detecting unit of a wearable electronic device according to an embodiment; 
         FIGS. 4A, 4B, 4C, and 4D  are views illustrating electrodes of a wearable electronic device according to an embodiment; 
         FIG. 5  is a circuit diagram illustrating a living body contact detecting unit of a wearable electronic device according to an embodiment; 
         FIG. 6  is a view illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment; 
         FIGS. 7A, 7B, 7C, and 7D  are views illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment; 
         FIGS. 8A, 8B, and 8C  are views illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment; 
         FIG. 9  is a flowchart illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment; 
         FIG. 10  is a flowchart illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment; 
         FIG. 11  is a flowchart illustrating an example of detecting a biometric signal by a wearable electronic device according to an embodiment; 
         FIG. 12A  is a front perspective view illustrating a wearable electronic device according to an embodiment; and 
         FIG. 12B  is a rear perspective view illustrating a wearable electronic device as shown in  FIG. 12A . 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures. 
     DETAILED DESCRIPTION 
       FIG. 1A  is a block diagram illustrating an electronic device  101  in a network environment  100   a  according to various embodiments. Referring to  FIG. 1A , the electronic device  101  in the network environment  100   a  may communicate with an electronic device  102  via a first network  198  (e.g., a short-range wireless communication network), or an electronic device  104  or a server  108  via a second network  199  (e.g., a long-range wireless communication network). According to an embodiment, the electronic device  101  may communicate with the electronic device  104  via the server  108 . According to an embodiment, the electronic device  101  may include a processor  120 , memory  130 , an input device  150 , a sound output device  155 , a display device  160 , an audio module  170 , a sensor module  176 , an interface  177 , a haptic module  179 , a camera module  180 , a power management module  188 , a battery  189 , a communication module  190 , a subscriber identification module (SIM)  196 , or an antenna module  197 . In some embodiments, at least one (e.g., the display device  160  or the camera module  180 ) of the components may be omitted from the electronic device  101 , or one or more other components may be added in the electronic device  101 . In some embodiments, some of the components may be implemented as single integrated circuitry. For example, the sensor module  176  (e.g., a fingerprint sensor, an iris sensor, or an illuminance sensor) may be implemented as embedded in the display device  160  (e.g., a display). 
     The processor  120  may execute, for example, software (e.g., a program  140 ) to control at least one other component (e.g., a hardware or software component) of the electronic device  101  coupled with the processor  120 , and may perform various data processing or computation. According to one embodiment, as at least part of the data processing or computation, the processor  120  may load a command or data received from another component (e.g., the sensor module  176  or the communication module  190 ) in volatile memory  132 , process the command or the data stored in the volatile memory  132 , and store resulting data in non-volatile memory  134 . According to an embodiment, the processor  120  may include a main processor  121  (e.g., a central processing unit (CPU) or an application processor (AP)), and an auxiliary processor  123  (e.g., a graphics processing unit (GPU), an image signal processor (ISP), a sensor hub processor, or a communication processor (CP)) that is operable independently from, or in conjunction with, the main processor  121 . Additionally or alternatively, the auxiliary processor  123  may be adapted to consume less power than the main processor  121 , or to be specific to a specified function. The auxiliary processor  123  may be implemented as separate from, or as part of the main processor  121 . 
     The auxiliary processor  123  may control at least some of functions or states related to at least one component (e.g., the display device  160 , the sensor module  176 , or the communication module  190 ) among the components of the electronic device  101 , instead of the main processor  121  while the main processor  121  is in an inactive (e.g., sleep) state, or together with the main processor  121  while the main processor  121  is in an active state (e.g., executing an application). According to an embodiment, the auxiliary processor  123  (e.g., an image signal processor or a communication processor) may be implemented as part of another component (e.g., the camera module  180  or the communication module  190 ) functionally related to the auxiliary processor  123 . 
     The memory  130  may store various data used by at least one component (e.g., the processor  120  or the sensor module  176 ) of the electronic device  101 . The various data may include, for example, software (e.g., the program  140 ) and input data or output data for a command related thereto. The memory  130  may include the volatile memory  132  or the non-volatile memory  134 . 
     The program  140  may be stored in the memory  130  as software, and may include, for example, an operating system (OS)  142 , middleware  144 , or an application  146 . 
     The input device  150  may receive a command or data to be used by other component (e.g., the processor  120 ) of the electronic device  101 , from the outside (e.g., a user) of the electronic device  101 . The input device  150  may include, for example, a microphone, a mouse, a keyboard, or a digital pen (e.g., a stylus pen). 
     The sound output device  155  may output sound signals to the outside of the electronic device  101 . The sound output device  155  may include, for example, a speaker or a receiver. The speaker may be used for general purposes, such as playing multimedia or playing record, and the receiver may be used for an incoming calls. According to an embodiment, the receiver may be implemented as separate from, or as part of the speaker. 
     The display device  160  may visually provide information to the outside (e.g., a user) of the electronic device  101 . The display device  160  may include, for example, a display, a hologram device, or a projector and control circuitry to control a corresponding one of the display, hologram device, and projector. According to an embodiment, the display device  160  may include touch circuitry adapted to detect a touch, or sensor circuitry (e.g., a pressure sensor) adapted to measure the intensity of force incurred by the touch. 
     The audio module  170  may convert a sound into an electrical signal and vice versa. According to an embodiment, the audio module  170  may obtain the sound via the input device  150 , or output the sound via the sound output device  155  or a headphone of an external electronic device (e.g., an electronic device  102 ) directly (e.g., wiredly) or wirelessly coupled with the electronic device  101 . 
     The sensor module  176  may detect an operational state (e.g., power or temperature) of the electronic device  101  or an environmental state (e.g., a state of a user) external to the electronic device  101 , and then generate an electrical signal or data value corresponding to the detected state. According to an embodiment, the sensor module  176  may include, for example, a gesture sensor, a gyro sensor, an atmospheric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, or an illuminance sensor. 
     The interface  177  may support one or more specified protocols to be used for the electronic device  101  to be coupled with the external electronic device (e.g., the electronic device  102 ) directly (e.g., wiredly) or wirelessly. According to an embodiment, the interface  177  may include, for example, a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, a secure digital (SD) card interface, or an audio interface. 
     A connecting terminal  178  may include a connector via which the electronic device  101  may be physically connected with the external electronic device (e.g., the electronic device  102 ). According to an embodiment, the connecting terminal  178  may include, for example, a HDMI connector, a USB connector, a SD card connector, or an audio connector (e.g., a headphone connector). 
     The haptic module  179  may convert an electrical signal into a mechanical stimulus (e.g., a vibration or motion) or electrical stimulus which may be recognized by a user via his tactile sensation or kinesthetic sensation. According to an embodiment, the haptic module  179  may include, for example, a motor, a piezoelectric element, or an electric stimulator. 
     The camera module  180  may capture a still image or moving images. According to an embodiment, the camera module  180  may include one or more lenses, image sensors, image signal processors, or flashes. 
     The power management module  188  may manage power supplied to the electronic device  101 . According to one embodiment, the power management module  188  may be implemented as at least part of, for example, a power management integrated circuit (PMIC). 
     The battery  189  may supply power to at least one component of the electronic device  101 . According to an embodiment, the battery  189  may include, for example, a primary cell which is not rechargeable, a secondary cell which is rechargeable, or a fuel cell. 
     The communication module  190  may support establishing a direct (e.g., wired) communication channel or a wireless communication channel between the electronic device  101  and the external electronic device (e.g., the electronic device  102 , the electronic device  104 , or the server  108 ) and performing communication via the established communication channel. The communication module  190  may include one or more communication processors that are operable independently from the processor  120  (e.g., the application processor (AP)) and supports a direct (e.g., wired) communication or a wireless communication. According to an embodiment, the communication module  190  may include a wireless communication module  192  (e.g., a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module) or a wired communication module  194  (e.g., a local area network (LAN) communication module or a power line communication (PLC) module). A corresponding one of these communication modules may communicate with the external electronic device via the first network  198  (e.g., a short-range communication network, such as Bluetooth™, wireless-fidelity (Wi-Fi) direct, or infrared data association (IrDA)) or the second network  199  (e.g., a long-range communication network, such as a cellular network, the Internet, or a computer network (e.g., LAN or wide area network (WAN)). These various types of communication modules may be implemented as a single component (e.g., a single chip), or may be implemented as multi components (e.g., multi chips) separate from each other. The wireless communication module  192  may identify and authenticate the electronic device  101  in a communication network, such as the first network  198  or the second network  199 , using subscriber information (e.g., international mobile subscriber identity (IMSI)) stored in the subscriber identification module  196 . 
     The antenna module  197  may transmit or receive a signal or power to or from the outside (e.g., the external electronic device). According to an embodiment, the antenna module may include one antenna including a radiator formed of a conductor or conductive pattern formed on a substrate (e.g., a printed circuit board (PCB)). According to an embodiment, the antenna module  197  may include a plurality of antennas. In this case, at least one antenna appropriate for a communication scheme used in a communication network, such as the first network  198  or the second network  199 , may be selected from the plurality of antennas by, e.g., the communication module  190 . The signal or the power may then be transmitted or received between the communication module  190  and the external electronic device via the selected at least one antenna. According to an embodiment, other parts (e.g., radio frequency integrated circuit (RFIC)) than the radiator may be further formed as part of the antenna module  197 . 
     At least some of the above-described components may be coupled mutually and communicate signals (e.g., commands or data) therebetween via an inter-peripheral communication scheme (e.g., a bus, general purpose input and output (GPIO), serial peripheral interface (SPI), or mobile industry processor interface (MIPI)). 
     According to an embodiment, commands or data may be transmitted or received between the electronic device  101  and the external electronic device  104  via the server  108  coupled with the second network  199 . The external electronic devices  102  and  104  each may be a device of the same or a different type from the electronic device  101 . According to an embodiment, all or some of operations to be executed at the electronic device  101  may be executed at one or more of the external electronic devices  102 ,  104 , or  108 . For example, if the electronic device  101  should perform a function or a service automatically, or in response to a request from a user or another device, the electronic device  101 , instead of, or in addition to, executing the function or the service, may request the one or more external electronic devices to perform at least part of the function or the service. The one or more external electronic devices receiving the request may perform the at least part of the function or the service requested, or an additional function or an additional service related to the request, and transfer an outcome of the performing to the electronic device  101 . The electronic device  101  may provide the outcome, with or without further processing of the outcome, as at least part of a reply to the request. To that end, a cloud computing, distributed computing, or client-server computing technology may be used, for example. 
       FIG. 1B  is a front perspective view  100   b  illustrating an electronic device according to an embodiment.  FIG. 1C  is a rear perspective view  100   c  illustrating an electronic device as shown in  FIG. 1B . 
     Referring to  FIGS. 1B and 1C , according to an embodiment, the wearable device  101   b  (e.g., the electronic device  101  of  FIG. 1A ) may include a housing  110   a  including a first surface (or front surface)  110 A, a second surface (or rear surface)  110 B, and a side surface  110 C surrounding the space between the first surface  110 A and the second surface  110 B and coupling members  150   a  and  160   a  connected to at least part of the housing  110   a  and configured to allow the electronic device  101   b  to be detachably worn on the user&#39;s body (e.g., his wrist or ankle). According to another embodiment (not shown), the housing may be a structure forming only a part of the first surface  110 A, the second surface  110 B, and the side surface  110 C of  FIG. 1 . According to an embodiment, at least part of the first surface  110 A may have a substantially transparent front plate  112   a  (e.g., a glass plate or polymer plate including various coat layers). The second surface  110 B may be formed of a substantially opaque rear plate  107   a . According to an embodiment, when the electronic device  101   b  includes a sensor module  165  disposed on the second surface  110 B, the rear plate  107   a  may at least partially include a transparent region. The rear plate  107   a  may be made of, e.g., laminated or colored glass, ceramic, polymer, metal (e.g., aluminum, stainless steel (STS), or magnesium), or a combination of at least two thereof. The side surface  110 C may be formed by a side bezel structure (or a “side member” or “bezel”)  106   a  that couples to the front plate  112   a  and the rear plate  107   a  and includes metal and/or polymer. According to an embodiment, the rear plate  107   a  and the side bezel structure  106   a  may be integrally formed together and include the same material (e.g., metal, such as aluminum). The coupling members  150   a  and  160   a  may be made of various materials in various shapes. A uni-body structure or multiple unit links which is flexible may be formed of fabric, leather, rubber, urethane, metal, ceramic, or a combination of at least two thereof. 
     According to an embodiment, the electronic device  101   b  may include at least one or more of a display  120   a  (refer to  FIG. 1D ), audio modules  105   a  and  108   a , a sensor module  165 , key input devices  102   a ,  103   a , and  104   a , and a connector hole  109   a . According to an embodiment, the electronic device  101   b  may exclude at least one of the components (e.g., the key input devices  102   a ,  103   a , and  104   a , connector hole  109   a , or sensor module  165 ) or may add other components. 
     According to an embodiment, the electronic device  101   b  may include a plurality of electrodes for measuring a biometric signal. At least one of the plurality of electrodes may be integrated with at least one of the key input device  102   a ,  103   a , or  104   a , the bezel  106   a , the display  120   a , or the housing  110   a . Among the key input devices, the wheel key  102   a  may include a rotary bezel. The display  120   a  may be exposed through a substantial portion of, e.g., the front plate  112   a . The display  120   a  may have a shape corresponding to the shape of the front plate  112   a , e.g., a circle, ellipse, or polygon. The display  120   a  may be coupled with, or disposed adjacent to, a touch detection circuit, a pressure sensor capable of measuring the strength (pressure) of touches, and/or fingerprint sensor. 
     According to an embodiment, the display  120   a  may include at least one transparent electrode for measuring biometric signals, where the transparent electrode is one of the plurality of electrodes for measuring biometric signals. 
     The audio modules  105   a  and  108   a  may include a microphone hole  105   a  and a speaker hole  108   a . The microphone hole  105   a  may have a microphone inside to obtain sounds produced outside the electronic device. According to an embodiment, there may be a plurality of microphones to be able to detect the direction of the sound. The speaker hole  108   a  may be used for an external speaker or a receiver for phone talks. According to an embodiment, a speaker may be included without the speaker hole (e.g., piezo speaker). 
     The sensor module  165  may generate an electrical signal or data value corresponding to an internal operating state or external environmental state of the electronic device  101   b . The sensor module  165 , e.g., a biometric sensor module  165  placed on the second surface  110 B of the housing  110   a , may include an electrocardiogram (ECG) sensor  165   a  including at least two electrodes a 1  and a 2  for ECG measurement and a photoplethysmogram (PPG) sensor  165   b  for heartrate measurement. The electronic device  101   b  may further include sensor modules not shown, e.g., at least one of a gesture sensor, a gyro sensor, an atmospheric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, or an illuminance sensor. 
     The key input devices  102   a ,  103   a , and  104   a  may include a wheel key  102   a  disposed on the first surface  110 A of the housing  110   a  that is rotatable in at least one direction and/or side key buttons  103   a  and  104   a  disposed on the side surface  110 C of the housing  110   a . The wheel key  102   a  may have a shape corresponding to the shape of the front plate  112   a . According to an embodiment, the electronic device  101   b  may exclude all or some of the above-mentioned key input devices  102   a ,  103   a , and  104   a  and the excluded key input devices  102   a ,  103   a , and  104   a  may be implemented in other forms, e.g., as soft keys on the display  120   a . The connector hole  109   a  may receive a connector (e.g., a universal serial bus (USB) connector) for transmitting and receiving power and/or data to/from an external electronic device. Another connector hole (not shown) may be included for receiving a connector for transmitting and receiving audio signals to/from the external electronic device. The electronic device  101   b  may further include a connector cover (not shown) to cover at least part of, e.g., the connector hole  109   a  so that undesirable materials (e.g. dirt) are prevented from entering the connector hole. 
     The coupling members  150   a  and  160   a  may detachably be fastened to at least portions of the housing  110   a  via locking members  151   a  and  161   a . The locking members  151   a  and  161   a  may include components or parts for coupling, such as pogo pins, and, according to an embodiment, may be replaced with protrusions or recesses formed on/in the coupling members  150   a  and  160   a . For example, the coupling members  150   a  and  160   a  may be coupled in such a manner as to be fitted into or over the recesses or protrusions formed on the housing  110 . The coupling members  150   a  and  160   a  may include one or more of a fastening member  152   a , fastening member coupling holes  153   a , a band guide member  154   a , and a band fastening ring  155   a.    
     The fastening member  152   a  may be configured to allow the housing  110   a  and the coupling members  150   a  and  160   a  to be fastened to the user&#39;s body (e.g., wrist or ankle). The fastening member coupling holes  153   a  may fasten the housing  110   a  and the coupling members  150   a  and  160   a  to the user&#39;s body, corresponding to the fastening member  152   a . The band guide member  154   a  may be configured to restrict movement of the fastening member  152   a  to a certain range when the fastening member  152   a  fits into one of the fastening member coupling holes  153   a , thereby allowing the coupling members  150   a  and  160   a  to be tightly fastened onto the user&#39;s body. The band fastening ring  155   a  may limit the range of movement of the coupling members  150   a  and  160   a , with the fastening member  152   a  fitted into one of the fastening member coupling holes  153   a.    
       FIG. 1D  is an exploded perspective view  100   d  illustrating the electronic device  101   b  of  FIG. 1B . 
     Referring to  FIG. 1D , an electronic device  101   b  (e.g., the electronic device  101  of  FIG. 1A ) may include a side bezel structure  210   a , a wheel key  220   a , a front plate  112   a , a display  120   a , a first antenna  250   a , a second circuit board  255   a , a supporting member  260   a  (e.g., a bracket), a battery  270   a , a printed circuit board  280   a , a sealing member  290   a , a rear plate  293   a , and coupling members  295   a  and  297   a . At least one of the components of the electronic device  101   b  may be the same or similar to at least one of the components of the electronic device  101   b  of  FIG. 1A or 1C  and no duplicate description is made below. The supporting member  260   a  may be disposed inside the electronic device  101   b  to be connected with the side bezel structure  210   a  or integrated with the side bezel structure  210   a . The supporting member  260   a  may be made of metal and/or non-metallic material (e.g., polymer). The display  120   a  may be joined onto one surface of the supporting member  260   a , and the printed circuit board  280   a  may be joined onto the opposite surface of the supporting member  260   a . Processor, memory, and/or interface may be mounted on the printed circuit board  280   a . The processor may include one or more of, e.g., a central processing unit, an application processor, a graphic processing unit (GPU), a sensor processor, or a communication processor. The processor may include a microprocessor or any suitable type of processing circuitry, such as one or more general-purpose processors (e.g., ARM-based processors), a Digital Signal Processor (DSP), a Programmable Logic Device (PLD), an Application-Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), a Graphical Processing Unit (GPU), a video card controller, etc. In addition, it would be recognized that when a general purpose computer accesses code for implementing the processing shown herein, the execution of the code transforms the general purpose computer into a special purpose computer for executing the processing shown herein. Certain of the functions and steps provided in the Figures may be implemented in hardware, software or a combination of both and may be performed in whole or in part within the programmed instructions of a computer. No claim element herein is to be construed under the provisions of 35 U.S.C. § 112(f), unless the element is expressly recited using the phrase “means for.” In addition, an artisan understands and appreciates that a “processor” or “microprocessor” may be hardware in the claimed disclosure. Under the broadest reasonable interpretation, the appended claims are statutory subject matter in compliance with 35 U.S.C. § 101. 
     The memory may include, e.g., a volatile or non-volatile memory. The interface may include, e.g., a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, a secure digital (SD) card interface, and/or an audio interface. The interface may electrically or physically connect the electronic device  101   b  with an external electronic device and may include a USB connector, an SD card/multimedia card (MMC) connector, or an audio connector. 
     The battery  270   a  may be a device for supplying power to at least one component of the electronic device  101   b . The battery  270   a  may include, e.g., a primary cell which is not rechargeable, a secondary cell which is rechargeable, or a fuel cell. At least a portion of the battery  270   a  may be disposed on substantially the same plane as the printed circuit board  280   a . The battery  270   a  may be integrally or detachably disposed inside the electronic device  101   b.    
     The first antenna  250   a  may be disposed between the display  120   a  and the supporting member  260   a . The first antenna  250   a  may include, e.g., a near-field communication (NFC) antenna, a wireless charging antenna, and/or a magnetic secure transmission (MST) antenna. The first antenna  250   a  may perform short-range communication with an external device, wirelessly transmit/receive power necessary for charging the electronic device  101   b , or transmit magnetic-based signals including payment data or short-range communication signals. According to an embodiment, the antenna structure for the first antenna  250   a  may be formed by a portion or combination of the side bezel structure  210   a  and/or the supporting member  260   a.    
     The second circuit board  255   a  may be disposed between the circuit board  280   a  and the rear plate  293   a . The second circuit board  255   a  may include an antenna, e.g., a near-field communication (NFC) antenna, a wireless charging antenna, and/or a magnetic secure transmission (MST) antenna. The second circuit board  255   a  may perform short-range communication with an external device, wirelessly transmit/receive power necessary for charging the electronic device  101   b , or transmit magnetic-based signals including payment data or short-range communication signals. According to an embodiment, an antenna structure for the antenna of the second circuit board  255   a  may be formed by a portion or combination of the side bezel structure  210   a  and/or the rear plate  293   a . According to an embodiment, when the electronic device  101   b  (e.g., the electronic device  101   b  of  FIG. 1B or 1C ) includes a sensor module (e.g., the sensor module  165  of  FIG. 1B ), a sensor element (e.g., a photoelectric conversion element or electrode pad) separate from the second circuit board  255   a  or the sensor circuit disposed on the second circuit board  255   a  may be disposed in the electronic device  101   b . For example, an electronic component referred to as the sensor module  165  may be disposed between the circuit board  280   a  and the rear plate  293   a.    
     The sealing member  290   a  may be positioned between the side bezel structure  210   a  and the rear plate  293   a . The sealing member  290   a  may be configured to block moisture or foreign materials from entering the space surrounded by the side bezel structure  210   a  and the rear plate  293   a.    
       FIG. 2  is a block diagram  200  schematically illustrating a wearable electronic device according to an embodiment. 
     Referring to  FIG. 2 , the wearable electronic device  201  (e.g., the electronic devices  101   a  to  101   d  of  FIGS. 1A to 1D ) may include a living body measuring unit  210 , a processor  220 , a memory  230 , and a display  260 . 
     According to an embodiment, the living body measuring unit  210  may detect contact of a portion of a living body to the electronic device and measure a biometric signal. The living body measuring unit  210  may include a living body interface unit  211 , a biometric data gathering unit  213 , and a living body contact detecting unit  215 . 
     According to an embodiment, the living body interface unit  211  may include at least one electrode directly contacting the living body. The living body interface unit  211  may electrically contact the living body to be able to exchange electrical signals between the living body and the biometric data gathering unit  213  or the living body contact detecting unit  215 . 
     According to an embodiment, the biometric data gathering unit  213  may detect an electrical signal received via the at least one electrode, thereby generating a biometric signal. The biometric signal may be transferred to the processor  220  for analysis of the biometric signal via an analog-to-digital converter (ADC). 
     According to an embodiment, the living body contact detecting unit  215  may determine the operation state for biometric signal measurement of the wearable electronic device  201  using two electrodes included in the living body interface unit  211  and may analyze the biometric signal generated from the biometric data gathering unit  213  to thereby measure the biometric signal. 
     According to an embodiment, the living body contact detecting unit  215  may apply different voltages to at least two electrodes when they are contacting the living body among for biometric signal measurement. The living body contact detecting unit  215  may output information indicating the operation state of the biometric signal measurement of the wearable electronic device  201  based on the voltage output from the at least two electrodes. 
     According to an embodiment, the living body contact detecting unit  215  may apply a first voltage to a first electrode when the first electrode among the at least two electrodes for biometric signal measurement contacts a first portion (e.g., wrist) of the living body. The living body contact detecting unit  215  may output information indicating that the operation state of the wearable electronic device  201  is a state of preparing for biometric signal measurement (this state may be referred to as a biometric signal measurement-ready state) based on the first voltage applied to the first electrode. When the first electrode and the third electrode, among the at least two electrodes contact a first portion (e.g., wrist) of the living body and a second portion (e.g., finger) of the living body contact, respectively, the living body contact detecting unit  215  may apply a second voltage different from the first voltage to each of the first electrode and the third electrode. The living body contact detecting unit  215  may output information indicating that the operation state of the wearable electronic device  201  is in a state where the biometric signal may be measured (this state may be referred to as a ‘biometric signal measurement-capable state’), based on the first voltage and the second voltage applied to the first electrode and the third electrode, respectively. 
     According to an embodiment, when the first electrode for measuring the biometric signal and the second electrode for applying a voltage contact the first portion (e.g., wrist) of the living body, the living body contact detecting unit  215  may form a path between the first electrode and the second electrode, thereby generating a closed loop between the first electrode and the second electrode via the first portion (e.g., wrist) of the living body. As the path is formed between the first electrode and the second electrode, the living body contact detecting unit  215  may output first information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-ready state, based on the first voltage applied from the second electrode to the first electrode. When the third electrode for measuring the biometric signal contacts the second portion (e.g., finger) of the living body while the first information is output, the living body contact detecting unit  215  may form an additional path between the second electrode and the third electrode. The living body contact detecting unit  215  may output second information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-capable state, based on the second voltage (different from the first voltage), which is applied from the second electrode to each of the first electrode and the third electrode. 
     According to an embodiment, when the first electrode and the third electrode contact no portion of the living body while the second information is output, the living body contact detecting unit  215  may output, from the second electrode, third information indicating that the operation state of the wearable electronic device is a state in which the biometric signal measurement has stopped (this state is referred to as a biometric signal measurement-stopped state), based on a voltage (e.g., 0V) output from the third electrode and the first electrode to which no voltage is applied. 
     According to an embodiment, the living body contact detecting unit  215  may measure the biometric signal using the difference between the potential values measured at the at least two electrodes for biometric signal measurement. 
     The living body contact detecting unit  215  is described below with reference to  FIG. 3 . 
     According to an embodiment, the processor  220  (e.g., the processor  120  of  FIG. 1A ) may control the overall operation of the wearable electronic device  201 . 
     According to an embodiment, the processor  220  (e.g., the processor  120  of  FIG. 1A ) may determine the operation state for biometric signal measurement of the wearable electronic device  201  based on information output from the living body contact detecting unit  215 . 
     According to an embodiment, upon receiving first information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-ready state, the processor  220  may switch to the biometric signal measurement (e.g., ECG measurement)-ready state. For example, the processor  220  may detect an application capable of biometric signal measurement and prepare for executing the same. In the biometric signal measurement-ready state, the processor  220  may measure the heartrate based on the signal received via the photoplethysmography (PPG) sensor ( 415  of  FIG. 4A ) mounted on the rear surface of the wearable electronic device  201 . 
     According to an embodiment, upon receiving second information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-capable state, the processor  220  may switch to the biometric signal measurement-capable state (e.g., the state where of ECG is measured). 
     According to an embodiment, upon receiving third information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-stopped state in the biometric signal measurement-capable state, the processor  220  may switch to the biometric signal measurement-stopped state. In this state, measurement of biometric signal may be stopped. 
     According to an embodiment, upon receiving first information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-ready state, the processor  220  may switch to the biometric signal measurement-ready state and then maintain the session for the biometric signal measurement-ready state. Upon receiving second information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-capable state while maintaining the session for the biometric signal measurement-ready state, the processor  220  may automatically switch to the biometric signal measurement-capable state and measure the biometric signal. 
     According to an embodiment, upon receiving first information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-ready state, the processor  220  may display that the wearable electronic device  201  is currently in the biometric signal measurement-ready state, via a user interface (UI), on the display  260 . Upon receiving second information indicating that the operation state of the wearable electronic device  201  is the biometric signal measurement-capable state while displaying that the wearable electronic device  201  is currently in the biometric signal measurement-ready state, the wearable electronic device  201  may display, via the UI on the display  260 , that the wearable electronic device  201  is in the state of currently measuring the biometric signal. 
     According to an embodiment, the memory  230  may store data (e.g., biometric signal data) from the wearable electronic device  201 . The memory  230  may be implemented in substantially the same or similar manner to the memory  130  described above in connection with  FIG. 1A . The memory  230  may be implemented as a non-volatile memory. 
     According to an embodiment, the display  260  may be implemented in substantially the same or similar manner to the display device  160  described above in connection with  FIG. 1A . The display  260  may display, via the UI, information indicating that the wearable electronic device is operating in the biometric signal measurement-ready state or information indicating that the wearable electronic device is operating in the state of measuring the biometric signal. When the electrodes of the wearable electronic device do not contact any portion of the living body in the state of measuring the biometric signal, the display  260  may display, via the UI, information indicating the biometric signal measurement-stopped state. 
       FIG. 3  is a block diagram  300  schematically illustrating a living body contact detecting unit of a wearable electronic device according to an embodiment. 
     Referring to  FIG. 3 , a living body contact detecting unit  310  (e.g., the living body contact detecting unit  215  of  FIG. 2 ) may include a plurality of electrodes  311 ,  312 , and  313 , an electrode connection detecting unit  330 , a bias unit  350 , and a measuring unit  370 . 
     According to an embodiment, the plurality of electrodes may include a first electrode  311  and a third electrode  313  for measuring a biometric signal and a second electrode  312  for applying a voltage to the first electrode  311  and/or the third electrode  313 . 
     According to an embodiment, the first electrode  311  and the third electrode  313  may include sensing electrodes capable of measuring a biometric signal at both ends (e.g., right hand and/or left hand) of the living body. 
     According to an embodiment, the first electrode  311  may be mounted in a position where a first portion (e.g., wrist) of the living body may come into contact with it, and the third electrode  313  may be mounted in a position where a second portion (e.g., finger) of the living body may come into contact with it. The third electrode  313  may be mounted in a position different from the positions where the first electrode  311  and the second electrode  312  are mounted, and the second portion (e.g., finger) of the living body may contact the third electrode  313 . 
     According to an embodiment, the second electrode  312  may be positioned on the same surface as the first electrode  311  or the third electrode  313 . For example, the second electrode  312  may be positioned on the same surface as the first electrode  311  and may contact the first portion (e.g., wrist) of the living body simultaneously with the first electrode  311 . 
     According to an embodiment, when the second electrode  312  contacts the first portion (e.g., wrist) of the living body simultaneously with the first electrode  311 , a path may be formed between the second electrode  312  and the first electrode  311 , thereby generating a closed loop between the second electrode  312  and the first electrode  311  via the first portion (e.g., wrist) of the living body, and a first voltage may be applied to the first electrode  311  via the path. 
     According to an embodiment, when the third electrode  313  contacts the second portion (e.g., finger) of the living body while the first voltage is applied to the first electrode  311  so that an additional path is formed between the second electrode  312  and the third electrode  313 , the second electrode  312  may apply the same second voltage to each of the first electrode  311  and the third electrode  313 . The second voltage may be lower than the first voltage. 
     According to an embodiment, the electrode connection detecting unit  330  may output information indicating the operation state for biometric signal measurement of the wearable electronic device (e.g., the wearable electronic device  201  of  FIG. 2 ), based on the voltage output from the first electrode  311  and/or the third electrode  313 . 
     According to an embodiment, the electrode connection detecting unit  330  may output first information indicating that the operation state of the wearable electronic device is the biometric signal measurement-ready state, based on the voltage (e.g., the first voltage or the second voltage) output from the first electrode  311 . 
     According to an embodiment, the electrode connection detecting unit  330  may output second information indicating that the operation state of the wearable electronic device is the biometric signal measurement-capable state, based on the second voltage output from the first electrode  311  and the third electrode  313 . 
     According to an embodiment, when the first electrode  311  and the third electrode  313  contact no portion of the living body, the electrode connection detecting unit  330  may output, from the second electrode  312 , third information indicating that the operation state of the wearable electronic device is the biometric signal measurement-stopped state, based on no voltage (e.g., 0V) output from the third electrode  313  and the first electrode  311 . 
     According to an embodiment, the electrode connection detecting unit  330  may include a first connection detecting unit  331 , which outputs a first comparison value resultant from comparing a first reference voltage with the first voltage and/or second voltage output from the first electrode  311 . The electrode connection detecting unit  330  may further include a second connection detecting unit  332 , which outputs a second comparison value resultant from comparing a second reference voltage with the second voltage output from the third electrode  313 . The electrode connection detecting unit  330  may summate the first comparison value output from the first connection detecting unit  331  and the second comparison value output from the second connection detecting unit  332  and output the summated value as information indicating the operation state for biometric signal measurement of the wearable electronic device. 
     According to an embodiment, the bias unit  350  may adjust the voltage to be applied to the first electrode  311  and/or third electrode  313 , when the paths are formed with the second electrode  312 , to the first voltage and/or the second voltage. 
     According to an embodiment, the bias unit  350  may be configured as an inverting summing amplifier. 
     According to an embodiment, the measuring unit  370  may measure the biometric signal using the difference between the potential values measured at the first electrode  311  and the third electrode  313 . 
     According to an embodiment, the measuring unit  370  may include a differential amplifier or an instrumentation amplifier (IA) having very high input impedance. 
       FIGS. 4A, 4B, 4C, and 4D  are views  400   a  to  400   d  illustrating electrodes of a wearable electronic device according to an embodiment. 
       FIG. 4A  illustrates a front surface  401   a  and rear surface  401   b  of a wearable electronic device  401 . 
     Referring to  FIG. 4A , a first electrode  411  (e.g., the first electrode  311  of  FIG. 3 ) for measuring biometric signals may be disposed on the rear surface  401   b  of the wearable electronic device  401 , and a second electrode  412  (e.g., the second electrode  312  of  FIG. 3 ) for applying voltage to the first electrode  411  and a third electrode  413  (e.g., the third electrode  313  of  FIG. 3 ) may be disposed on the same surface as the first electrode  411 . The third electrode  413  for measuring biometric signals may be disposed on a side surface of the wearable electronic device  401  which may be contacted by the other hand of the user when the wearable electronic device  401  is worn on one hand. A photoplethysmography (PPG) sensor  415  for heartrate measurement may be mounted in the center on the rear surface  401   b  of the wearable electronic device  401 . 
     As shown in  FIG. 4B , the wearable electronic device  401  may be worn on the user&#39;s wrist, and a first portion (e.g., the user&#39;s wrist) of the user&#39;s body may come in contact with the first electrode  411  and the second electrode  412 , and a second portion (e.g., the user&#39;s finger) of the user&#39;s body may come in contact with the third electrode  413  placed on the right side surface of the wearable electronic device  401 . 
     The third electrode which may be touched by the second portion (e.g., finger) of the user&#39;s body, with the wearable electronic device  401  worn on the user&#39;s wrist and the first portion (e.g., wrist) of the user&#39;s body contacting the first electrode  411  and the second electrode  412 , may be disposed in various positions. For example, the third electrode  413  may be disposed on the left side surface of the wearable electronic device  401  or, as shown in  FIG. 4B , on the right side surface. 
     Alternatively, as shown in  FIG. 4C , the third electrode  413  may be included, as a transparent electrode, in the display  460  (e.g., the display  120   a  of  FIG. 1D  or the display  260  of  FIG. 2 ) of the wearable electronic device  401  and be contacted by a second portion (e.g., finger) of the user&#39;s body. 
     Alternatively, as shown in  FIG. 4D , the third electrode  413  may be disposed in the bezel  402  (e.g.,  106   a  of  FIG. 1B ) of the wearable electronic device  401  and be contacted by the second portion (e.g., finger) of the user&#39;s body. When the wearable electronic device  401  is bezel-less, the third electrode  413  may be disposed on the housing (e.g.,  110   a  of  FIG. 1B ) of the wearable electronic device  401  and be contacted by the second portion (e.g., finger) of the user&#39;s body. 
       FIG. 5  is a circuit diagram  500  illustrating a living body contact detecting unit of a wearable electronic device according to an embodiment.  FIG. 5  is a circuit diagram of the living body contact detecting unit  310  of the wearable electronic device of  FIG. 3 . 
     Referring to  FIG. 5 , the living body contact detecting unit  510  may include a plurality of electrodes  511 ,  512 , and  513 , a plurality of buffers  523  having high input impedance, which process the voltage output from the first electrode  511  and third electrode  513  for biometric signal measurement, electrode connection detecting units  531  and  532 , a bias unit  550 , and a measuring unit  570  measuring the biometric signal based on the first electrode  511  and the third electrode  513 . 
     The plurality of electrodes may include a first electrode  511  and a third electrode  513  for measuring a biometric signal and a second electrode  512  for applying a predetermined voltage to the first electrode  511  and the third electrode  513 . 
     The electrode connection detecting units  531  and  532  may include a first connection detecting unit  531  comparing a first reference voltage with the first voltage and/or second voltage output from the first electrode  511  and a second connection detecting unit  532  comparing a second reference voltage with the second voltage output from the third electrode  513 . 
     The first connection detecting unit  531  may include a first comparator  531   a  and a second comparator  531   b  and may set the first reference voltage TH_L of the first comparator  531   a  to “0.4V” and the first reference voltage TH_H of the second comparator  531   b  to “1.4V.” 
     According to an embodiment, the first reference voltage TH_L of the first comparator  531   a  and the first reference voltage TH_H of the second comparator  531   b  may be adjusted by the processor (e.g., the processor  220  of  FIG. 2 ) for enhancing the detecting capability. The processor may adjust the first reference voltage TH_L of the first comparator  531   a  and the first reference voltage TH_H of the second comparator  531   b  according to the operation state for biometric signal measurement of the wearable electronic device. When the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-ready state, the processor may adjust a range of the first reference voltage TH_L of the first comparator  531   a  and the first reference voltage TH_H of the second comparator  531   b  to a first range and, when the operation state of biometric signal measurement of the wearable electronic device is the state of measuring the biometric signal, the processor may adjust a range of the first reference voltage TH_L of the first comparator  531   a  and the first reference voltage TH_H of the second comparator  531   b  to a second range which is smaller or larger than the first range. 
     The second connection detecting unit  532  may include a first comparator  532   a  and a second comparator  532   b  and may set the second reference voltage TH_H of the first comparator  532   a  to “1.4V” and the second reference voltage TH_L of the second comparator  532   b  to “0.4V.” 
     According to an embodiment, the second reference voltage TH_H of the first comparator  532   a  and the second reference voltage TH_L of the second comparator  532   b  may be adjusted by the processor (e.g., the processor  220  of  FIG. 2 ) for enhancing the detecting capability. The processor may adjust the second reference voltage TH_H of the first comparator  532   a  and the second reference voltage TH_L of the second comparator  532   b  according to the operation state for biometric signal measurement of the wearable electronic device. When the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-ready state, the processor may adjust a range between the second reference voltage TH_H of the first comparator  532   a  and the second reference voltage TH_L of the second comparator  532   b  to a third range and, when the operation state of biometric signal measurement of the wearable electronic device is the state of measuring the biometric signal, the processor may adjust a range between the second reference voltage TH_H of the first comparator  532   a  and the second reference voltage TH_L of the second comparator  532   b  to a fourth range which is smaller or larger than the third range. 
     According to an embodiment, the comparator (e.g., the first comparator  531   a  and second comparator  531   b  of the first connection detecting unit  531  and/or the first comparator  532   a  and second comparator  532   b  of the second connection detecting unit  532 ) may compare the voltages applied to the non-inverting (+) input terminal and inverting (−) input terminal and output the result of the comparison. For example, when the voltage applied to the non-inverting (+) input terminal is higher than the voltage applied to the inverting (−) input terminal, the comparator may output “1” and, when the voltage applied to the non-inverting (+) input terminal is identical to or lower than the voltage applied to the inverting (−) input terminal, the comparator may output “0.” The comparator (e.g., the first comparator  531   a  and second comparator  531   b  of the first connection detecting unit  531  and/or the first comparator  532   a  and second comparator  532   b  of the second connection detecting unit  532 ) may compare the voltages applied to the non-inverting (+) input terminal and inverting (−) input terminal based on other various comparison conditions and output the results. 
     According to an embodiment, the properties of the electrode connection detecting units  531  and  532  may be adjusted according to external factors (e.g., the user&#39;s characteristics (e.g., the degree of dryness of hand) and/or ambient environment (e.g., temperature). 
     According to an embodiment, the properties of the electrode connection detecting units  531  and  532  may be adjusted by increasing the input resistance (Rin) of the front end of the buffer  523  or by changing the operation voltage (e.g., 0.4V) set as default for the comparator (e.g., the first comparator  531   a  and second comparator  531   b  of the first connection detecting unit  531  and/or the first comparator  532   a  and second comparator  532   b  of the second connection detecting unit  532 ). 
     According to an embodiment, the properties of the electrode connection detecting units  531  and  532  may be changed by the user&#39;s selection or automatically according to the result of detection by a detecting unit capable of detecting external factors (e.g., the user&#39;s characteristics (e.g., the degree of hand dryness) and/or ambient environment (e.g., temperature)). 
     The electrode connection detecting units  531  and  532  may output the information, which results from summating the information output from the first connection detecting unit  531  and the information output from the second connection detecting unit  532  and list such pieces of information in order, as information (e.g., first information or second information) for indicating the operation state for biometric signal measurement of the wearable electronic device (e.g., the wearable electronic device  201  of  FIG. 2 ). 
     The bias unit  550  may include an inverting summing amplifier, the average voltage of the first electrode  511  and the third electrode  513  may be input to the inverting (−) terminal of the amplifier, and the Vbias input to the non-inverting (+) terminal may be set to 0.9V. The amplifier may be configured to output 0V through up to 1.8V. 
     The plurality of buffers  523  are high-impedance elements and may allow high voltage to be applied to the respective front nodes B 1  and B 2  of the first electrode  511  and the third electrode  513 . 
     Due to their high impedance, the plurality of buffers  523  may stop the current flowing through the front nodes B 1  and B 2  of the first electrode  511  and the third electrode  513  from flowing towards the plurality of buffers  523 , thereby preventing the biometric measurement (e.g., ECG measurement) signal from weakening due to a drop of the voltage applied to the front nodes B 1  and B 2  of the first electrode  511  and the third electrode  513 . 
     The plurality of buffers  523  may be used for precise biometric measurement (e.g., ECG measurement) signals in the case where the contact resistance increases due to the user&#39;s dry skin or a small electrode area as in the wearable electronic device. 
     The plurality of buffers  523  may not be included in the living body contact detecting unit  510  in the case the electrode impedance is maintained to be lower than a predetermined reference in the wearable electronic device. The plurality of buffers  523  are elements for minimizing influence by the electrode impedance and may be omitted in the system where the electrode impedance is maintained to be lower than a predetermined reference. 
       FIG. 6  is a view  600  illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment.  FIG. 6  is a view illustrating the biometric signal measurement-stopped state in which no living body contact is made in the wearable electronic device.  FIG. 6  illustrates the same living body contact detecting unit  610  as that of  FIG. 5 , except that different reference numbers are used. 
     Referring to  FIG. 6 , with the living body is not in contact with both the first electrode  611  and the third electrode  613  for biometric measurement, the first electrode  611  and the third electrode  613  each may output a voltage of 0V. The first comparator  631   a  and the second comparator  631   b  included in the first connection detecting unit  631  may compare the voltage (0V) output from the first electrode  611  with a first reference voltage (TH_L=0.4V, TH_H=1.4V) and output “NL=1, NH=0” as information according to the result of comparison. The first comparator  632   a  and the second comparator  632   b  included in the second connection detecting unit  632  may compare the voltage (0V) output from the third electrode  613  with a second reference voltage (TH_H=1.4V, TH_L=0.4V) and output “PL=1, PH=0” as information according to the result of comparison. “PL, PH, NL, NH=1010” ( 690 ), which results from summating the information (PL, PH) output from the second connection detecting unit  632  and the information (NL, NH) output from the first connection detecting unit  631  and listing the pieces of information in order, may be output, as third information, to the processor (e.g., the processor  220  of  FIG. 2 ). The processor may detect that the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-stopped state, based on the third information “PL, PH, NL, NH=1010” ( 690 ) output from the living body contact detecting unit  610 . 
       FIGS. 7A, 7B, 7C, and 7D  are views  700   a  to  700   d  illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment.  FIGS. 7A to 7D  are views illustrating the biometric signal measurement-ready state in the wearable electronic device and show the process from the time when the wearable electronic device contacts the first portion (e.g., wrist) of the living body to the final stable state in which information indicating contact of the first portion (e.g., wrist) of the living body to the wearable electronic device may be output.  FIGS. 7A to 7D  illustrate the same living body contact detecting unit  710  as that of  FIGS. 5 and 6 , except that different reference numbers are used. 
     Referring to  FIG. 7A , when the wearable electronic device is worn on the user&#39;s wrist, the first electrode  711  and second electrode  712  positioned on the same surface may contact the first portion (e.g., wrist) of the living body. When the first electrode  711  and the second electrode  712  contact the first portion (e.g., wrist) of the living body so that a path A 1  is formed between the first electrode  711  and the second electrode  712 , the second electrode  712  may apply a first voltage, e.g., maximum voltage Vsat of 1.8V, to the first electrode  711  (a 1 ). 
     Referring to  FIG. 7B , when the maximum voltage, 1.8V, is applied from the second electrode  712  to the first electrode  711 , a voltage of 1.8V output from the first electrode  711  may be input to each of the first comparator  731   a  and the second comparator  731   b  included in the first connection detecting unit  731  (a 2 ). As the third electrode  713  which the living body does not contact outputs 0V, the first comparator  732   a  and the second comparator  732   b  included in the second connection detecting unit  732  may maintain input of 0V which is output from the third electrode  713 . The average voltage, 0.9V, of the first electrode  711  and the third electrode  713  may be input to the inverting (−) terminal of the bias unit  760  (a 3 ). 
     Referring to  FIG. 7C, 1.8V  which is input to each of the first comparator  731   a  and the second comparator  731   b  included in the first connection detecting unit  731  may be compared with the first reference voltage (TH_L=0.4V, TH_H=1.4V), and “NL=0, NH=1,” as information according to the result of comparison, may be output (a 4 ). The first comparator  732   a  and the second comparator  732   b  included in the second connection detecting unit  732  may compare the voltage (0V) output from the third electrode  713  with a second reference voltage (TH_H=1.4V, TH_L=0.4V) and maintain the output of “PL=1, PH=0” as information according to the result of comparison. 
     By the process shown in  FIGS. 7A to 7C , when the final stable state is reached as shown in  FIG. 7D , “PL, PH, NL, NH=1001” ( 790 ), which results from summating the information (PL, PH) output from the second connection detecting unit  732  and the information (NL, NH) output from the first connection detecting unit  731  and listing the pieces of information in order, may be output, as first information, to the processor (e.g., the processor  220  of  FIG. 2 ). The processor may detect that the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-ready state, based on the first information “PL, PH, NL, NH=1001” ( 790 ) output from the living body contact detecting unit  710 . 
       FIGS. 8A, 8B, and 8C  are views  800   a  to  800   c  illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment.  FIGS. 8A to 8C  are views illustrating the biometric signal measurement-capable state in the wearable electronic device and show the process from the time when the wearable electronic device contacts the second portion (e.g., finger) of the living body, with the first portion (e.g., wrist) of the living body in contact with the wearable electronic device, to the final stable state in which information indicating contact of both the first portion (e.g., wrist) and second portion (e.g., finger) of the living body to the wearable electronic device may be output.  FIGS. 8A to 8C  illustrate the same living body contact detecting unit  810  as that of  FIGS. 5 to 7 , except that different reference numbers are used. 
     Referring to  FIG. 8A , when the third electrode  813  contacts the second portion (e.g., finger) of the living body while the first information, “PL, PH, NL, NH=1001” ( 790 ) indicating that the wearable electronic device contacts the first portion (e.g., wrist) of the living body is output from the living body contact detecting unit  810 , an additional path A 2  may be formed between the second electrode  812  and the third electrode  813 . When the additional path A 2  is formed between the second electrode  812  and the third electrode  813 , the voltage at the third electrode  813  may rise (b 1 ) so that the voltage output to the second connection detecting unit  832  may go up (b 2 ), and the average voltage of the first electrode  811  and the third electrode  813  at the inverting (−) terminal increases (b 3 ) so that the output voltage of the bias unit  860  may drop (b 4 ). 
     Referring to  FIG. 8B , as the average voltage input to the inverting (−) terminal of the bias unit  860  rises, if the output voltage of the bias unit  860  decreases, the voltage applied from the second electrode  812  to the first electrode  811  may drop (b 5 ) so that the voltage output from the first connection detecting unit  831  may decrease (b 6 ). 
     Referring to  FIGS. 8A and 8B , when the output value of the bias unit  860  is varied as the third electrode  813  contacts the second portion (e.g., finger) of the living body, with the first portion (e.g., wrist) of the living body simultaneously contacting the first electrode  811  and the second electrode  812 , the average voltage between the first electrode  811  and the third electrode  813  input to the inverting (−) terminal of the bias unit  860  may be adjusted to a predetermined voltage (e.g., 0.9V) so that the same second voltage is applied from the second electrode  812  to each of the first electrode  811  and the third electrode  813  as shown in  FIG. 8C . When the average voltage is adjusted to the predetermined voltage (e.g., 0.9V), the second voltage applied to the first electrode  811  and the third electrode  813  may become 0.4V to 1.4V. 
     Referring to  FIG. 8C , the voltage at the first electrode  811  may be decreased to a target voltage (e.g., 0.9V), and the voltage at the third electrode  813  may be increased to the target voltage (e.g., 0.9V) (b 7 ) so that the average voltage may be adjusted to the predetermined voltage (e.g., 0.9V) (b 8 ). When the average voltage (e.g., 0.9V) adjusted to the predetermined voltage is input to the inverting (−) terminal of the bias unit  860 , the bias unit  860  may output the target voltage (e.g., 0.9V) (b 9 ). As the second electrode  812  applies the second voltage (e.g., 0.9V) to each of the first electrode  811  and the third electrode  813 , the second voltage (e.g., 0.9V) may be output to the first connection detecting unit  831  and the second connection detecting unit  832 . 
     The second voltage (e.g., 0.9V) which is input to each of the first comparator  831   a  and the second comparator  831   b  included in the first connection detecting unit  831  may be compared with the first reference voltage (TH_L=0.4V, TH_H=1.4V), and “NL=0, NH=0,” as information according to the result of comparison, may be output (b 10 ). The second voltage (e.g., 0.9V) which is input to each of the first comparator  832   a  and the second comparator  832   b  included in the second connection detecting unit  832  may be compared with the second reference voltage (TH_H=1.4V, TH_L=0.4V), and the output of “PL=0, PH=0,” which is the information according to the result of comparison, may be maintained. “PL, PH, NL, NH=0000” ( 890 ), which is the second information resultant from summating the information (PL, PH) output from the second connection detecting unit  832  and the information (NL, NH) output from the first connection detecting unit  831  and listing the pieces of information in order, may be output to the processor (e.g., the processor  220  of  FIG. 2 ). The processor may detect that the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-capable state, based on the second information “PL, PH, NL, NH=0000” ( 890 ) output from the living body contact detecting unit  810 . 
     According to an embodiment, a wearable electronic device (e.g., the wearable electronic device  201  of  FIG. 2 ) comprises at least two electrodes (e.g., the first electrode  312  and third electrode  313  of  FIG. 3 ) for measuring a biometric signal, a living body contact detecting unit (e.g., the living body contact detecting unit  215  of  FIG. 2  or the living body contact detecting unit  310  of  FIG. 3 ) configured to apply a voltage to at least one electrode contacting a living body among the at least two electrodes and output information indicating an operation state for biometric signal measurement of the wearable electronic device based on a voltage output from the at least one electrode, and a processor (e.g., the processor  120  of  FIG. 1A  or the processor  220  of  FIG. 2 ) configured to determine the operation state for biometric signal measurement of the wearable electronic device, based on the information received from the living body contact detecting unit. 
     According to an embodiment, the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ) is configured to, when a first electrode (e.g., the first electrode  311  of  FIG. 3 ) among the at least two electrodes for biometric signal measurement contacts first portion of the living body, apply a first voltage to the first electrode and, when the first electrode and a third electrode (e.g., the third electrode  313  of  FIG. 3 ), among the at least two electrodes contact the first portion of the living body and a second portion of the living body, respectively, apply a second voltage different from the first voltage to each of the first electrode and the third electrode. 
     According to an embodiment, the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ) is configured to, when a first electrode for the biometric signal measurement and a second electrode for applying a voltage contact a first portion of the living body, output first information indicating that the operation state of the wearable electronic device is a biometric signal measurement-ready state, based on a first voltage applied to the first electrode; and when a third electrode for the biometric signal measurement contacts a second portion of the living body while the first information is output, output second information indicating that the operation state of the wearable electronic device is a biometric signal measurement-capable state, based on a second voltage applied to each of the first electrode and the third electrode. 
     According to an embodiment, the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ) is configured to, when the first electrode and the third electrode contact no portion of the living body, output third information indicating that the operation state of the wearable electronic device is a biometric signal measurement-stopped state, based on no voltage output from the third electrode and the first electrode. 
     According to an embodiment, the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ) includes the at least two electrodes including a first electrode (e.g., the first electrode  311  of  FIG. 3 ) and a third electrode (e.g., the third electrode  313  of  FIG. 3 ) for biometric signal measurement and a second electrode (e.g., the second electrode of  FIG. 2 ) for applying a voltage to the first electrode and the third electrode, an electrode connection detecting unit (e.g., the electrode connection detecting unit  330  of  FIG. 3 ) configured to output first information indicating that the operation state of the wearable electronic device is a biometric signal measurement-ready state based on a first voltage output from the first electrode and output second information indicating that the operation state of the wearable electronic device is a biometric signal measurement-capable state based on a second voltage output from the third electrode, a bias unit (e.g., the bias unit  350  of  FIG. 3 ) configured to adjust a voltage to be applied from the second electrode to the first electrode and/or the third electrode to the first voltage and/or the second voltage, and a measuring unit (e.g., the measuring unit  370  of  FIG. 3 ) configured to measure the biometric signal using one or more differences between potential values measured at the first electrode and the third electrode. 
     According to an embodiment, the electrode connection detecting unit (e.g., the electrode connection detecting unit  330  of  FIG. 3 ) includes a first connection detecting unit (e.g., the first connection detecting unit  331  of  FIG. 3 ) configured to compare a first reference voltage with the first voltage and/or the second voltage output from the first electrode and a second connection detecting unit (e.g., the second connection detecting unit  332  of  FIG. 3 ) configured to compare a second reference voltage with the second voltage output from the third electrode. 
     According to an embodiment, among the at least two electrodes, a first electrode and a second electrode is placed in positions of the wearable electronic device, where the first electrode and the second electrode can contact a first portion of the living body and, among the at least two electrodes, a third electrode can contact a second portion of the living body in a position different from the positions of the first electrode and the second electrode. 
     According to an embodiment, the wearable electronic device further comprises a memory configured to store biometric information and a display displaying the biometric information. 
     According to an embodiment, the processor is configured to, upon receiving first information indicating that the operation state of the wearable electronic device is a biometric signal measurement-ready state, switch to the biometric signal measurement-ready state, maintain a session for the biometric signal measurement-ready state and, upon receiving second information indicating that the operation state of the wearable electronic device is a biometric signal measurement-capable state while maintaining the session for the biometric signal measurement-ready state, automatically switch to the biometric signal measurement-capable state to measure the biometric signal. 
     According to an embodiment, the processor is configured to, upon receiving first information indicating that the operation state of the wearable electronic device is a biometric signal measurement-ready state, display information related to the biometric signal measurement-ready state of the wearable electronic device on a user interface (UI) and, upon receiving second information indicating that the operation state of the wearable electronic device is a biometric signal measurement-capable state while displaying the information related to the biometric signal measurement-ready state on the UI, display information related to the biometric signal measurement-capable state of the wearable electronic device on the UI. 
     According to an embodiment, the processor is configured to, upon receiving third information indicating that the operation state of the wearable electronic device is a biometric signal measurement-stopped state, switch to the biometric signal measurement-stopped state. 
       FIG. 9  is a flowchart  900  illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment. The living body contact detecting operations may include operations  901  to  905 . The living body contact detecting operations may be performed by a wearable electronic device (e.g., the electronic device  101  of  FIG. 1 ), at least one processor (e.g., the processor  120  of  FIG. 1A ) of the electronic device, the wearable electronic device  201  of  FIG. 2 , or the processor (e.g., the processor  220  of  FIG. 2  and/or the living body contact detecting unit  215  of  FIG. 2 ) of the wearable electronic device. According to an embodiment, at least one of operations  901  to  905  may be omitted, or some operations may be performed in a different order, or other operations may be added. 
     Referring to  FIG. 9 , in operation  901 , the wearable electronic device may apply different voltages to the at least two electrodes based on at least one electrode contacting the living body among at least two electrodes for biometric signal measurement. 
     According to an embodiment, when the first electrode (e.g., the first electrode  311  of  FIG. 3 ) for biometric signal measurement and the second electrode (e.g., the second electrode  312  of  FIG. 3 ) for applying voltage in the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ) contacts a first portion (e.g., wrist) of the living body, the second electrode may apply the first voltage (e.g., the maximum voltage, e.g., 1.8V) to the first electrode. 
     According to an embodiment, when the third electrode (e.g., the third electrode  313  of  FIG. 3 ) for biometric signal measurement contacts a second portion (e.g., finger) of the living body while the first portion (e.g., wrist) of the living body is in contact with the first electrode (e.g., the first electrode  312  of  FIG. 3 ) and the second electrode (e.g., the second electrode  313  of  FIG. 3 ) in the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ), the second electrode may apply the second voltage (e.g., 0.9V), which is lower than the first voltage, to each of the first electrode and the third electrode. 
     In operation  903 , the wearable electronic device may output information indicating the operation state of the biometric signal measurement of the wearable electronic device based on the voltage output from the at least two electrodes. 
     According to an embodiment, when the first electrode (e.g., the first electrode  311  of  FIG. 3 ) for biometric signal measurement and the second electrode (e.g., the second electrode  312  of  FIG. 3 ) for applying voltage in the living body contact detecting unit (e.g., the living body contact detecting unit  315  of  FIG. 3 ) contacts the first portion (e.g., wrist) of the living body so that the second electrode applies the first voltage (e.g., the maximum voltage, e.g., 1.8V) to the first electrode, first information indicating that the operation state of the wearable electronic device is the biometric signal measurement-ready state may be output based on the first voltage. 
     According to an embodiment, when the third electrode (e.g., the third electrode  313  of  FIG. 3 ) for biometric signal measurement contacts the second portion (e.g., finger) of the living body while the first portion (e.g., wrist) of the living body is in contact with the first electrode (e.g., the first electrode  312  of  FIG. 3 ) and the second electrode (e.g., the second electrode  313  of  FIG. 3 ) in the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ) so that the second electrode applies the second voltage (e.g., 0.9V) to each of the first electrode and the third electrode, second information indicating that the operation state of the wearable electronic device is the biometric signal measurement-capable state may be output based on the second voltage. 
     According to an embodiment, when the first electrode and the third electrode contact no portion of the living body while the second information is output from the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ), third information indicating that the wearable electronic device contacts no portion of the living body may be output based on the voltage (e.g., 0V) output from the first electrode and the third electrode to which no voltage is applied from the second electrode. 
     In operation  905 , the wearable electronic device may determine the operation state for biometric signal measurement of the wearable electronic device based on the information indicating the operation state for biometric signal measurement of the wearable electronic device. 
     According to an embodiment, it may be determined that the operation state of the wearable electronic device is the biometric signal measurement-ready state, based on the first information output from the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ). 
     According to an embodiment, it may be determined that the operation state of the wearable electronic device is the biometric signal measurement-capable state, based on the second information output from the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ). 
     According to an embodiment, it may be determined that the operation state of the wearable electronic device is the biometric signal measurement-stopped state, based on the third information output from the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ). 
       FIG. 10  is a flowchart  1000  illustrating an example of detecting living body contact by a wearable electronic device according to an embodiment. The living body contact detecting operations may include operations  1001  to  1005 . The living body contact detecting operations may be performed by a wearable electronic device (e.g., the electronic device  101  of  FIG. 1 ), at least one processor (e.g., the processor  120  of  FIG. 1A ) of the electronic device, the wearable electronic device  201  of  FIG. 2 , or the processor (e.g., the processor  220  of  FIG. 2  and/or the living body contact detecting unit  215  of  FIG. 2 ) of the wearable electronic device. According to an embodiment, at least one of operations  1001  to  1005  may be omitted, or some operations may be performed in a different order, or other operations may be added. 
     Referring to  FIG. 10 , in operation  1001 , upon detecting first information indicating that the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-ready state as the wearable electronic device contacts the first portion (e.g., wrist) of the living body, the wearable electronic device may switch to the biometric signal measurement-ready state. According to an embodiment, upon receiving the first information (e.g., the first information (PL, PH, NL, NH=1001) ( 790 ) of  FIG. 7D ), the wearable electronic device may search for an application (e.g., ECG application) for biometric signal measurement and prepare to execute the application. 
     According to an embodiment, upon switching to the biometric signal measurement-ready state in response to reception of the first information (PL, PH, NL, NH=1001) ( 790 ) of  FIG. 7D ), the wearable electronic device may measure at least one of heartrate, oxygen saturation, blood pressure, stress level, or sleep information based on the signal received via the PPG sensor (e.g.,  415  of  FIG. 4A ) mounted on the rear surface of the wearable electronic device in the biometric signal measurement-ready state and display information about at least one of the measured heartrate, oxygen saturation, blood pressure, stress level, or sleep information on the display (e.g., the display  260  of  FIG. 2 ). 
     According to an embodiment, the wearable electronic device may switch to the biometric signal measurement-ready state based on living body approaching information detected by the PPG sensor and the information (PL, PH, NL, NH=1001) ( 790 ) of  FIG. 7D ) detected by the electrodes. In the case where the living body approaching information is detected using the PPG sensor alone, a predetermined number of samples or more may be needed, so that it may take time to determine the biometric signal measurement-ready state. Thus, when the electrodes are used together with the PPG sensor, it may be quickly determined whether it is in the biometric signal measurement-ready state. When the wearable electronic device has difficulty in judging contact of the living body, such as when the user wears the wearable electronic device with a shirt in-between, the user&#39;s skin is dry, the ambient temperature is low, or the user&#39;s arm is hairy, it may be quickly and precisely determined whether it is in the biometric signal measurement-ready state by using the PPG sensor along with the electrodes. 
     In operation  1003 , upon detecting second information indicating that the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-capable state as the first portion (e.g., wrist) of the living body and the second portion (e.g., finger) of the living body contact the wearable electronic device, the wearable electronic device may switch to the biometric signal measurement-capable state. 
     According to an embodiment, upon receiving the second information (e.g., the second information (PL, PH, NL, NH=0000)( 890 ) of  FIG. 8C ), the wearable electronic device may execute an application (e.g., ECG application) for biometric signal measurement, receive the biometric signal measured from the measuring unit (e.g., the measuring unit  370  of  FIG. 3 ) of the living body contact detecting unit (e.g., the living body contact detecting unit  310  of  FIG. 3 ), and display information about the biometric signal on the display (e.g., the display  260  of  FIG. 2 ). 
     In operation  1005 , upon detecting third information (e.g., the third information (PL, PH, NL, NH=1010)( 690 ) of  FIG. 6 ) indicating that the operation state for biometric signal measurement of the wearable electronic device is the biometric signal measurement-stopped state as the wearable electronic device contacts no portion of the living body, the wearable electronic device may switch to the biometric signal measurement-stopped state. According to an embodiment, in this state, the contact, to the wearable electronic device, of the first portion (e.g., wrist) of the living body and the second portion (e.g., finger) of the living body is released. Thus, the third information may be information indicating the release of the contact of the first portion (e.g., wrist) of the living body and/or the second portion (e.g., finger) of the living body. 
     According to an embodiment, the wearable electronic device may switch to the biometric signal measurement-stopped state based on living body approaching information detected by the PPG sensor and the information (e.g., the third information (PL, PH, NL, NH=(PL, PH, NL, NH=1010) ( 690 ) of  FIG. 6 ) detected by the electrodes. 
     In the case where the living body approaching information is detected using the PPG sensor alone, a predetermined number of samples or more may be needed, so that it may take time to determine the biometric signal measurement-stopped state. Thus, when the electrodes, which may immediately detect contact and/or non-contact of the living body, are used together with the PPG sensor, it may be quickly determined whether it is in the biometric signal measurement-stopped state. When the electrodes are used, a DC-based method is used, rather than an AC-based method which is poor at detecting the contact or non-contact of the first portion and second portion of the living body to the wearable electronic device, due to a path formed between the two electrodes which are supposed to be electrically insulated from each other. When the electrodes are used by the DC-based method, no additional noise may be caused unlike in the AC-based method which applies an alternating current. 
     As the wearable electronic device precisely determines contact or non-contact to portions (e.g., the first portion and the second portion) of the living body as shown in  FIG. 10 , it may aid in precisely determining the user&#39;s context, thereby increasing the reliability of user authentication and payment service. As the wearable electronic device quickly determines the contact and non-contact to the portion (e.g., the first portion and second portion) of the living body based on the approaching information from the PPG sensor and the information from the electrodes, it may be possible to determine the context in an complementary manner (e.g. complementary to the PPG sensor) even when a temporary non-contact occurs to the body portion (e.g., the first portion and second portion), leading to better usability. 
       FIG. 11  is a flowchart  1110  illustrating an example of detecting a biometric signal by a wearable electronic device according to an embodiment. 
       FIG. 11  illustrates a first interval A in which the wearable electronic device (e.g., the wearable electronic device  201  of  FIG. 2 ) is worn on the user&#39;s wrist and is in the biometric signal measurement-ready state, a second interval B in which while the first interval A is maintained, a finger contacts the third electrode of the wearable electronic device so that the biometric signal is automatically measured, and a third interval C in which contact of a finger to the third electrode of the wearable electronic device is not detected. 
     In the first interval A, the wearable electronic device (e.g., the wearable electronic device  201  of  FIG. 2 ) is worn on the first portion (e.g., wrist) of the living body, and the wearable electronic device is currently in the biometric signal measurement-ready state. In the first interval A, as the first electrode  1111  (e.g., the first electrode  711  of  FIGS. 7A to 7D ) contacts the first portion (e.g., wrist) of the living body, the first electrode  1111  outputs the maximum voltage, e.g., 1.8V, which is applied from the second electrode (e.g., the second electrode  712  of  FIGS. 7A to 7D ) which, together with the first electrode  1111 , forms a path, and the third electrode  1113  (e.g., the third electrode  713  of  FIGS. 7A to 7D ) which the living body does not contact may output 0V. As the first electrode  1111  outputs the maximum voltage, 1.8V, and the third electrode  1113  outputs 0V in the first interval A, the wearable electronic device (e.g., the living body contact detecting unit  215  of  FIG. 3 ) may output first information (e.g., PL, PH, NL, NH=1001) indicating the biometric signal measurement-ready state. 
     In the second interval B, the third electrode  1113  (e.g., the third electrode  813  of  FIGS. 8A to 8C ) contacts the second portion (e.g., finger) of the living body while the first interval A, where the wearable electronic device is worn on the first portion (e.g., wrist) of the living body, is maintained. In response to contact of the second portion (e.g., finger) of the living body to the third electrode  1113 , the wearable electronic device may automatically measure the biometric signal. 
     The second interval B may include an initial stabilization interval B 1 , a biometric signal measurement interval B 2 , and a biometric signal measurement termination interval B 3 . 
     The initial stabilization interval B 1  may include a first time b 1 , a second time b 2 , a third time b 3 , and a fourth time b 4  and may include a predetermined time interval (e.g., 1 second) or less. 
     The first time b 1  is the time when the second portion (e.g., finger) of the living body actually contacts the third electrode  1113 , with the wearable electronic device worn on the first portion (e.g., wrist) of the living body. 
     The second time b 2 , which may occur a predetermined time interval (e.g., 10 ms or less) after the first time b 1 , is the time when the wearable electronic device detects the contact of the second portion (e.g., finger) of the living body to the third electrode  1113 , with the wearable electronic device worn on the first portion (e.g., wrist) of the living body. As the first electrode  1111  (e.g., the first electrode  811  of  FIGS. 8A to 8C ) contacts the first portion (e.g., wrist) of the living body, and the third electrode  1113  contacts the second portion (e.g., finger) of the living body, the first electrode  1111  and the third electrode  1113  may output the voltage which is applied from the second electrode which forms paths with each of the first electrode  1111  and the third electrode  1113 . The interval between the first time b 1  and the second time b 2  is a stabilization interval for outputting a target voltage (e.g., 0.9V) to each of the first electrode  1111  and the third electrode  1113  from the second electrode. Thus, at the second time b 2 , the second electrode outputs the target voltage (e.g., 0.9V) to each of the first electrode  1111  and the third electrode  1113 , so that the second information (e.g., PL, PH, NL, NH=0000) indicating that the wearable electronic device is in the biometric signal measurement-capable state may be output. At the second time b 2 , a preparation signal for biometric signal measurement may be transferred to the measuring unit (e.g., the measuring unit  370  of  FIG. 3 ) of the biometric signal detecting unit that measures the biometric signal. 
     The third time b 3  is the time when the biometric signal may be measured, and the interval between the second time b 2  and the third time b 3  may be referred to as a signal saturation interval. 
     The fourth time b 4  is the time when valid signal values for biometric signal measurement may be gathered. During the interval (e.g., 10 ms) between the third time b 3  and the fourth time b 4 , excessive response signal values received as the voltage value is varied may be disregarded and, from the fourth time b 4 , stable and effective signal values for biometric signal measurement may be obtained. 
     In the interval B 2  for gathering signals for biometric signal measurement, stable and effective signal values b 7  for biometric signal measurement may be received during a predetermined time interval (e.g., 30 ms) and the biometric signal may be measured. During the interval B 2  for gathering signals for biometric signal measurement, the measuring unit (e.g., the measuring unit  370  of  FIG. 3 ) may measure the biometric signal using the difference between the voltages at the first electrode  1111  and the third electrode  1113 , based on the effective signal values for biometric signal measurement, received during the predetermined time (e.g., 30 ms). 
     The biometric signal measurement termination interval B 3  may include a fifth time b 5  which is the time when the contact of the second portion (e.g., finger) of the living body to the third electrode  1113  is substantially released while the wearable electronic device stays worn on the first portion (e.g., wrist) of the living body and a sixth time b 6  which is the time when the wearable electronic device detects the release of the contact of the second portion (e.g., finger) of the living body to the third electrode  1111  while the wearable electronic device stays worn on the first portion (e.g., wrist) of the living body. 
     The third interval C is an interval during which the wearable electronic device is currently in the biometric signal measurement-ready state as the contact of the second portion (e.g., finger) of the living body to the third electrode  1113  (e.g., the third electrode  713  of  FIGS. 7A to 7D ) is released, with the wearable electronic device worn on the first portion (e.g., wrist) of the living body. In the third interval C, as in the first interval A, the wearable electronic device (e.g., the living body contact detecting unit  215  of  FIG. 3 ) may output the first information (e.g., PL, PH, NL, NH=1001) indicating the biometric signal measurement-ready state. 
       FIG. 12A  is a front perspective view  1200   a  illustrating a wearable electronic device according to an embodiment.  FIG. 12B  is a rear perspective view  1200   b  illustrating the wearable electronic device of  FIG. 12A . 
     Referring to  FIGS. 12A and 12B , a pair of earbuds  1201 , which is the wearable electronic device, may include one earbud  1201   a . The one earbud  1201   a  may include a plurality of electrodes  1211 ,  1212 , and  1213  for detecting biometric signals. The plurality of electrodes may include a first electrode  1211  (e.g., the first electrode  311  of  FIG. 3 ) and a third electrode  1213  (e.g., the third electrode  313  of  FIG. 3 ) for biometric signal measurement and a second electrode  1212  (e.g., the second electrode  312  of  FIG. 3 ) for applying voltage to the first electrode  1211  and/or the third electrode  1213 . The earbud  1201  may include the configuration of  FIGS. 2 and 3 . 
     When the pair of earbuds  1201  or one earbud  1201   a  of the pair  1201  is inserted to the user&#39;s ear, the first electrode  1211  and the second electrode  1212  positioned on the same surface of the earbud  1201   a  contact a first portion (e.g., ear) of the living body, a path may be formed between the first electrode  1211  and the second electrode  1212 . And, as the first electrode  1211  outputs the voltage which is applied from the second electrode  1212 , the earbud pair  1201  may turn into the biometric signal measurement-ready state. While the earbud pair  1201  remains in the biometric signal measurement-ready state, if the third electrode  1213  contacts a second portion (e.g., finger) of the living body, an additional path may be formed between the second electrode  1212  and the third electrode  1213 , and the first electrode  1211  and the third electrode  1213  each may output the voltage which is applied from the second electrode  1212 , so that the earbud pair  1201  may automatically measure the biometric signal. The result of biometric signal measurement may be output via the electronic device communicating with the earbud pair  1210 . 
     Although the wearable electronic device is exemplified as a watch as shown in  FIGS. 1B to 1D and 4A to 4D  and as earbuds as shown in  FIGS. 12A and 12B , embodiments of the disclosure may also apply to other embodiments such as glasses which are worn on the user&#39;s face and contact the living body. 
     The watch, as the wearable electronic device, may also be worn on the user&#39;s ankle, not only on the user&#39;s wrist, and may detect living body contact and measuring biometric signals in the same manner. 
     According to an embodiment, a method for detecting contact of a living body to a wearable electronic device (e.g., the wearable electronic device  201  of  FIG. 2 ) can comprise applying a voltage to at least one electrode contacting the living body among at least two electrodes for biometric signal measurement, outputting information indicating an operation state for biometric signal measurement of the wearable electronic device based on another voltage output from the at least one electrode, and determining the operation state of the biometric signal measurement of the wearable electronic device based on the information indicating the operation state of the biometric signal measurement of the wearable electronic device. 
     According to an embodiment, applying the voltage include, when a first electrode among the at least two electrodes for biometric signal measurement contacts a first portion of the living body, applying a first voltage to the first electrode and, when the first electrode and a third electrode, among the at least two electrodes contact the first portion of the living body and a second portion of the living body, respectively, applying a second voltage, different from the first voltage, to each of the first electrode and the third electrode. 
     According to an embodiment, outputting the information include, when a first electrode for the biometric signal measurement and a second electrode for applying the voltage contact a first portion of the living body, outputting first information indicating that the operation state of the wearable electronic device is a biometric signal measurement-ready state, based on a first voltage applied to the first electrode and, when a third electrode for the biometric signal measurement contacts a second portion of the living body while the first information is output, outputting second information indicating that the operation state of the wearable electronic device is a biometric signal measurement-capable state, based on a second voltage applied to each of the first electrode and the third electrode. 
     According to an embodiment, the method further comprises, when the first electrode and the third electrode contact no portion of the living body, outputting third information indicating that the operation state of the wearable electronic device is a biometric signal measurement-stopped state, based on no voltage output from the third electrode and the first electrode. 
     According to an embodiment, among the at least two electrodes, a first electrode and a second electrode are be placed in positions of the wearable electronic device, where the first electrode and the second electrode can contact a first portion of the living body. 
     According to an embodiment, among the at least two electrodes, a third electrode can contact a second portion of the living body in a position different from the positions of the first electrode and the second electrode. 
     According to an embodiment, the method further comprise, upon receiving first information indicating that the operation state of the wearable electronic device is a biometric signal measurement-ready state, switching to the biometric signal measurement-ready state, maintaining a session for the biometric signal measurement-ready state and, upon receiving second information indicating that the operation state of the wearable electronic device is a biometric signal measurement-capable state while maintaining the session for the biometric signal measurement-ready state, automatically switching to the biometric signal measurement-capable state to measure the biometric signal. 
     According to an embodiment, the method further comprise, upon receiving first information indicating that the operation state of the wearable electronic device is a biometric signal measurement-ready state, displaying information related to the biometric signal measurement-ready state of the wearable electronic device on a user interface (UI) and, upon receiving second information indicating that the operation state of the wearable electronic device is a biometric signal measurement-capable state while displaying the information related to the biometric signal measurement-ready state on the UI, displaying information related to the biometric signal measurement-capable state of the wearable electronic device on the UI. 
     According to an embodiment, the method further comprise, upon receiving third information indicating that the operation state of the wearable electronic device is a biometric signal measurement-stopped state, switching to the biometric signal measurement-stopped state. 
     The electronic device according to various embodiments may be one of various types of electronic devices. The electronic devices may include, for example, a portable communication device (e.g., a smart phone), a computer device, a portable multimedia device, a portable medical device, a camera, a wearable device, or a home appliance. According to an embodiment of the disclosure, the electronic devices are not limited to those described above. 
     It should be appreciated that various embodiments of the disclosure and the terms used therein are not intended to limit the technological features set forth herein to particular embodiments and include various changes, equivalents, or replacements for a corresponding embodiment. With regard to the description of the drawings, similar reference numerals may be used to refer to similar or related elements. It is to be understood that a singular form of a noun corresponding to an item may include one or more of the things, unless the relevant context clearly indicates otherwise. As used herein, each of such phrases as “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B, or C,” “at least one of A, B, and C,” and “at least one of A, B, or C,” may include all possible combinations of the items enumerated together in a corresponding one of the phrases. As used herein, such terms as “1st” and “2nd,” or “first” and “second” may be used to simply distinguish a corresponding component from another, and does not limit the components in other aspect (e.g., importance or order). It is to be understood that if an element (e.g., a first element) is referred to, with or without the term “operatively” or “communicatively”, as “coupled with,” “coupled to,” “connected with,” or “connected to” another element (e.g., a second element), it means that the element may be coupled with the other element directly (e.g., wiredly), wirelessly, or via a third element. 
     As used herein, the term “module” may include a unit implemented in hardware, software, or firmware, and may interchangeably be used with other terms, for example, “logic,” “logic block,” “part,” or “circuitry”. A module may be a single integral component, or a minimum unit or part thereof, adapted to perform one or more functions. For example, according to an embodiment, the module may be implemented in a form of an application-specific integrated circuit (ASIC). 
     Various embodiments as set forth herein may be implemented as software (e.g., the program  140 ) including one or more instructions that are stored in a storage medium (e.g., internal memory  136  or external memory  138 ) that is readable by a machine (e.g., the electronic device  101 ). For example, a processor (e.g., the processor  120 ) of the machine (e.g., the electronic device  101 ) may invoke at least one of the one or more instructions stored in the storage medium, and execute it, with or without using one or more other components under the control of the processor. This allows the machine to be operated to perform at least one function according to the at least one instruction invoked. The one or more instructions may include a code generated by a compiler or a code executable by an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. Wherein, the term “non-transitory” simply means that the storage medium is a tangible device, and does not include a signal (e.g., an electromagnetic wave), but this term does not differentiate between where data is semi-permanently stored in the storage medium and where the data is temporarily stored in the storage medium. 
     According to an embodiment, a method according to various embodiments of the disclosure may be included and provided in a computer program product. The computer program products may be traded as commodities between sellers and buyers. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read only memory (CD-ROM)), or be distributed (e.g., downloaded or uploaded) online via an application store (e.g., Play Store™), or between two user devices (e.g., smart phones) directly. If distributed online, at least part of the computer program product may be temporarily generated or at least temporarily stored in the machine-readable storage medium, such as memory of the manufacturer&#39;s server, a server of the application store, or a relay server. 
     According to various embodiments, each component (e.g., a module or a program) of the above-described components may include a single entity or multiple entities. According to various embodiments, one or more of the above-described components may be omitted, or one or more other components may be added. Alternatively or additionally, a plurality of components (e.g., modules or programs) may be integrated into a single component. In such a case, according to various embodiments, the integrated component may still perform one or more functions of each of the plurality of components in the same or similar manner as they are performed by a corresponding one of the plurality of components before the integration. 
     According to various embodiments, operations performed by the module, the program, or another component may be carried out sequentially, in parallel, repeatedly, or heuristically, or one or more of the operations may be executed in a different order or omitted, or one or more other operations may be added. 
     There may be provided a storage medium storing instructions configured to, when executed by at least one processor, enable the at least one processor to perform operations such as applying a voltage to at least one electrode contacting the living body among at least two electrodes for biometric signal measurement, outputting information indicating an operation state for biometric signal measurement of the wearable electronic device based on another voltage output from the at least one electrode, and determining the operation state of the biometric signal measurement of the wearable electronic device based on the information indicating the operation state of the biometric signal measurement of the wearable electronic device. 
     As is apparent from the foregoing description, according to certain embodiments, a buffer having high input impedance is used, so that the bias unit, which is a voltage source, may operate at very low output current. Further, as compared with the conventional operation method in which voltage is measured by applying current, it is possible to prolong the battery life of the wearable electronic device. Since no current is applied between the two electrodes in certain situations, no additional noise (IR voltage drop by current*contact resistance) occurs. It is also possible to measure the biometric signal while simultaneously detecting contact of a body portion to the wearable electronic device using the two electrodes. 
     The embodiments herein are provided merely for better understanding of the disclosure, and the disclosure should not be limited thereto or thereby. It should be appreciated by one of ordinary skill in the art that various changes in form or detail may be made to the embodiments without departing from the scope of the disclosure defined by the following claims. 
     Certain of the above-described embodiments of the present disclosure can be implemented in hardware, firmware or via the execution of software or computer code that can be stored in a recording medium such as a CD ROM, a Digital Versatile Disc (DVD), a magnetic tape, a RAM, a floppy disk, a hard disk, or a magneto-optical disk or computer code downloaded over a network originally stored on a remote recording medium or a non-transitory machine readable medium and to be stored on a local recording medium, so that the methods described herein can be rendered via such software that is stored on the recording medium using a general purpose computer, or a special processor or in programmable or dedicated hardware, such as an ASIC or FPGA. As would be understood in the art, the computer, the processor, microprocessor controller or the programmable hardware include memory components, e.g., RAM, ROM, Flash, etc. that may store or receive software or computer code that when accessed and executed by the computer, processor or hardware implement the processing methods described herein.