Abstract:
A pulse wave measuring device includes: a connector that is disposed on a main unit; an external sensor that includes an external light-emitting module radiating light to a human body to be measured and an external light-receiving module receiving at least one of reflected light and transmitted light originating from the external light-emitting module and the human body so as to measure a pulse wave; an first controller that switches the external light-emitting module ON and OFF; an second controller that switches the external light-receiving module ON and OFF; and an external sensor connection determination section that determines a connection between the external sensor and the connector in accordance with a transient response of the external light-receiving module, wherein, after the external sensor connection determination section determines that the external sensor is connected to the connector, a measurement of the pulse wave by using the external sensor is started.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2007-337135, filed Dec. 27, 2007, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates to a pulse wave measuring device for measuring a pulse wave while being put on a human body. 
         [0004]    2. Description of the Related Art 
         [0005]    One of devices that measure vital-sign information about a user while being put on a body, such as a wrist, is a pulse wave measuring device that optically measures a pulse wave. 
         [0006]    A pulse wave is a waveform arising when a change in the pressure of blood stemming from contraction of the heart travels to peripheral blood vessels, and the waveform is primarily induced by a change in the flow of arterial blood. However, amounts of hemoglobin in blood acquired at an area to be measured also change in the same manner as does the flow of arterial blood, and hence a pulse wave can be measured by means of measuring the amounts of hemoglobin. 
         [0007]    One technique for measuring a pulse wave is a photoelectric pulse wave detection method. A light absorption factor of hemoglobin changes depending on the wavelength of light. Light in a waveband (ranging from visible light to near infrared light), which is absorbed by hemoglobin, is radiated from a light-emitting element (LED: a light-emitting diode, and the like). Differences in the intensity of reflected light or transmitted light induced by a change in blood flow are detected by a light-receiving element (a photodiode, and the like), thereby detecting a pulse wave. 
         [0008]    Depending on a waveband to be used, a change in blood flow of an arteriole near skin is captured by means of pulse wave detection complying with the photoelectric pulse wave detection method; hence, pulse wave measurement is suitable for measurement performed in an area (a finger, a palm, an ear lobe, and the like) where a plurality of arterioles are present. (For example, refer to JP-A-2003-169780 (KOKAI)). 
         [0009]    A device for measuring a pulse wave without placing a burden on the user in a daily life has already been put into commercial production. For instance, a main unit of a pulse wave measuring device is put on a wrist like a wrist watch, and only a pulse wave sensor is withdrawn from the main unit by means of a cable. The pulse wave sensor is wrapped around a finger, to thus measure a pulse wave in a palm. However, wrapping the pulse wave sensor around a finger hinders daily living activities, such as washing hands and gripping an object. For this reason, it is desirable to measure a pulse wave at a wrist where the main unit of the pulse wave measuring device is put. However, signal intensity acquired through photoelectric pulse wave measurement performed at a wrist is weaker than that acquired through measurement performed in a palm, and there is the case where measurement cannot be performed stably depending on the user or a state. 
         [0010]    In a pulse wave measurement device that enables selective use of a removable pulse wave sensor for finger use and a wrist pulse wave sensor for measuring a pulse wave at a wrist, it is laborious for the user to specify and switch the pulse wave sensor to be used for measurement. 
         [0011]    Therefore, it is appropriate that the pulse wave measuring device should determine connection/disconnection of the finger pulse wave sensor and automatically switch operation of the pulse wave measuring device so as to measure a pulse wave at a finger when the finger pulse wave sensor is connected and at a wrist when the finger pulse wave sensor is not connected. 
         [0012]    It is conceivable that an electrical connection detection mechanism will be provided in a connector for detecting connection of the finger pulse wave sensor. Proposed as such is a mechanism having a logical output circuit using; for instance, a GND pin provided in a cable terminal, thereby detecting connection/disconnection of an external input device (see; for instance, JP-A-2006-33127(KOKAI)). Provision of a mechanical connection detection mechanism is also conceivable. For instance, a connector equipped with a contact switch for detecting connection is proposed (see; for instance, JP-A-2006-80816(KOKAI)). 
         [0013]    However, miniaturizing the connector of the pulse wave measuring device of wrist watch type as small as possible is desirable. 
         [0014]    When the detection technique, such as that described in connection with JP-A-2006-33127(KOKAI), is adopted, provision of an electrode for detecting connection is required, which results in an increase in the number of electrodes as well as the number of signal lines and an increase in the size of the connector. 
         [0015]    When the detection technique, such as that described in connection with JP-A-2006-80816(KOKAI), is adopted, a mechanical mechanism is provided; hence, there is a disadvantage of requirement of a space for the mechanism and complication of the mechanism itself. 
       SUMMARY OF THE INVENTION 
       [0016]    According to an aspect of the present invention, there is provided a pulse wave measuring device including: a main unit; a connector that is disposed on the main unit; an external sensor that includes an external light-emitting module emitting light to a human body to be measured and an external light-receiving module receiving at least one of reflected light and transmitted light originating from the external light-emitting module and the human body so as to measure a pulse wave; an first controller that controls the external light-emitting module; an second controller that controls the external light-receiving module; and an external sensor connection determination section that determines a connection between the external sensor and the connector in accordance with a transient response of the external light-receiving module, the transient response being produced by activation of the external light-emitting module and the external light-receiving module, wherein, after the external sensor connection determination section determines that the external sensor is connected to the connector, a measurement of the pulse wave by using the external sensor is started. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0017]    A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. 
           [0018]      FIG. 1  is a block diagram showing the functional configuration of an exemplary pulse wave measuring device of an embodiment of the present invention; 
           [0019]      FIG. 2  is an exemplary schematic view showing example attachment of the pulse wave measuring device of the embodiment of the present invention; 
           [0020]      FIG. 3  is an exemplary schematic view showing example attachment of the pulse wave measuring device of the embodiment of the present invention; 
           [0021]      FIG. 4  is an exemplary schematic view showing an example configuration of an external pulse wave sensor of the embodiment of the present invention; 
           [0022]      FIG. 5  is an exemplary schematic view showing an example configuration of an internal pulse wave sensor of the embodiment of the present invention; 
           [0023]      FIG. 6  is an exemplary flowchart showing processing operation of the embodiment of the present invention; 
           [0024]      FIG. 7  is an exemplary flowchart showing processing operation of the embodiment of the present invention; 
           [0025]      FIG. 8  is an exemplary flowchart showing processing operation of the embodiment of the present invention; 
           [0026]      FIG. 9  is an exemplary view showing an example response of a light-receiving element produced when the external pulse wave sensor is not connected; 
           [0027]      FIG. 10  is an exemplary view showing an example response of the light-receiving element produced when the external pulse wave sensor is connected; 
           [0028]      FIG. 11  is an exemplary view showing an example response of the light-receiving element produced when the external pulse wave sensor is connected; 
           [0029]      FIG. 12  is an exemplary view showing an example output from the light-receiving element produced when the external pulse wave sensor is attached to a finger; 
           [0030]      FIG. 13  is an exemplary flowchart showing processing operation achieved in a second embodiment; and 
           [0031]      FIG. 14  is an exemplary view showing an example response of a light-receiving element produced after emitting of a light-emitting element of the second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    The best mode for implementing a pulse wave measuring device of the present invention will be described below by reference to the drawings. Throughout the drawings, like areas are assigned like reference numerals, and overlapping explanations are omitted. 
         [0033]      FIG. 1  is a block diagram showing the functional configuration of a pulse wave measuring device of an embodiment of the present invention. 
         [0034]    As shown in  FIG. 1 , a pulse wave measuring device broadly includes a pulse wave measuring device main unit  100  incorporating a control section and a determination section (both of which will be described later), an external pulse wave sensor  110 , and an internal pulse wave sensor  120  built in the pulse wave measuring device main unit  100 . 
         [0035]    The external pulse wave sensor  110  is connected to the pulse wave measuring device main unit  100  by way of a cable  113  and a connector  114 . The external pulse wave sensor  110  incorporates a light-emitting element  111  that radiates light of given intensity (light including; for instance, infrared light) to an area to be measured and a light-receiving element  112  that receives the light, which has been radiated by the light-emitting element  111  and reflected from the area to be measured, and converts the received light into an electric signal. 
         [0036]    The light-emitting element  111  and the light-receiving element  112  are connected to the cable  113  and further connected to a connector  114  provided in the pulse wave measuring device main unit  100  by way of the cable  113 . A signal output from the light-receiving element  112  is input to a pulse wave detection section  130 , where a pulse interval is detected from a pulse wave signal that is generated by extracting, amplifying, and shaping a photoelectric pulse wave component. 
         [0037]    An internal pulse wave sensor  120  built in the pulse wave measuring device main unit  100  has a second light-emitting element  121  that radiates light of given intensity (light including; for instance, infrared light) to an area to be measured and a second light-receiving element  122  that receives light, which has been radiated by the second light-emitting element  121  and reflected from the area to be measured, and converts the received light into an electric signal. A signal output from the second light-receiving element  122  is input to the pulse wave detection section  130 , where a pulse interval is detected from a pulse wave signal that is generated by extracting, amplifying, and shaping a photoelectric pulse wave component. 
         [0038]    A light-emitting element control section  101 , a light-receiving element control section  102 , a second light-emitting element control section  103 , a second light-receiving element control section  104 , an external pulse wave sensor connection determination section  105 , an external pulse wave sensor attachment determination section  106 , and an internal pulse wave sensor attachment determination section  107  are provided in the pulse wave measuring device main unit  100 . 
         [0039]    The light-emitting element control section  101  is connected to the light-emitting element  111  by way of the connector  114  and the cable  113 , thereby controlling operation of the light-emitting element  111 ; and sends an electric signal to the light-emitting element  111 . 
         [0040]    Likewise, the light-receiving element control section  102  is connected to the light-receiving element  112  by way of the connector  114  and the cable  113 ; controls operation of the light-receiving element  112 ; and receives the electric signal from the light-receiving element  112 . 
         [0041]    The light-emitting element control section  101  and the light-receiving element control section  102  are connected to the external pulse wave sensor connection determination section  105 , respectively, and determine the state of connection of the external pulse wave sensor  110 . Further, determination information from the external pulse wave sensor connection determination section  105  is transmitted to the external pulse wave sensor attachment determination section  106  and determines the state of attachment of the external pulse wave sensor  110 . Further, determination information from the external pulse wave sensor connection determination section  105  is transmitted to the internal pulse wave sensor attachment determination section  107 , as well. 
         [0042]    The second light-emitting element  121  is connected to the second light-emitting element control section  103 , and the function of the second light-emitting element is controlled. Likewise, the second light-receiving element  122  is connected to the second light-receiving element control section  104 , and the function of the second light-receiving element is controlled, and an electric signal from the second light-receiving element  122  is received. 
         [0043]    The second light-emitting element control section  103  and the second light-receiving element control section  104  are connected to the external pulse wave sensor connection determination section  105 , respectively. 
         [0044]      FIGS. 2 and 3  are diagrammatic views showing an example of attachment of the pulse wave measuring device of the embodiment of the present invention.  FIG. 2  shows an example in which a pulse wave is measured at the thick of a finger with the pulse wave measuring device main unit  100  put on a wrist and the external pulse wave sensor  110  put on a finger.  FIG. 3  shows an example in which a pulse wave is measured at a wrist by the internal pulse wave sensor  120  while the pulse wave measuring device main unit  100  is put on the wrist. 
         [0045]    In the external pulse wave sensor  110 , the light-emitting element  111  and the light-receiving element  112  are arranged side by side as shown in  FIG. 4 . The sensor is wrapped around the forefinger, and the like, by means of a belt (not shown); for instance, a Hook-and-Loop fastener, and a pulse wave is measured at the thick of the forefinger. 
         [0046]    In the internal pulse wave sensor  120 , the second light-emitting element  121  and the second light-receiving element  122  are arranged side by side on the back of the pulse wave measuring device main unit  100  as shown in  FIG. 5 . The internal pulse wave sensor  120  measures a pulse wave at the wrist contacting the back of the pulse wave measuring device main unit  100 . 
         [0047]    The light-emitting element  111  and the second light-emitting element  121  radiate light in a waveband at which hemoglobin exhibits an 2 characteristic (visible light to near infrared light) to a skin that is an area to be measured, and the light-receiving element  112  or the second light-receiving element  122  detects differences in intensity of reflected light or transmitted light induced by a change in blood flow. Accordingly, the light-receiving element  112  preferably has a characteristic that exhibits superior sensitivity at a peak wavelength of light emitted by the light-emitting element  111 , and the second light-receiving element  122  preferably has a characteristic that exhibits superior sensitivity at a peak wavelength of light emitted by the second light-emitting element  121 . The light-emitting element  111  and the second light-emitting element  121  preferably use a light-emitting diode, and the like; and the light-receiving element  112  and the second light-receiving element  122  preferably use a photodiode, a phototransistor, and the like. However, other light-emitting means and light-receiving means may also be used. 
         [0048]      FIG. 6  is a flowchart for describing processing operation of the pulse wave measuring device of the embodiment of the present invention. Descriptions are provided hereinbelow along the flowchart. 
         [0049]    First, when the power of the pulse wave measuring device is turned on, the device is started in a standby mode (step S 10 ). When the user presses a measurement start button (not shown) provided on the pulse wave measuring device to perform measurement initiation operation (step S 11 ), the light-receiving element control section  102  energizes the light-receiving element  112  to turn on the light-receiving element  112  (step S 12 ). When preliminary energization is unnecessary to activate of the light-receiving element  112 , processing with respect to step S 12  may be omitted. 
         [0050]    Next, the pulse wave measuring device is in the standby mode for a given time in which the operation of the light-receiving element  112  becomes stable (step S 13 ). When the light-receiving element  112  to be used does not need a wait time before achieving stability, processing with respect to step S 13  may be omitted. 
         [0051]    The light-emitting element control section  101  sends the electric signal; and tries to cause the light-emitting element  111  to emit light (step S 14 ). By means of reaction of the light-receiving element  112  caused after emission of light from the light-emitting element  111 , the external pulse wave sensor connection determination section  105  and the external pulse wave sensor attachment determination section  106  determine connection and attachment of the external pulse wave sensor  110  (step S 15 ). 
         [0052]    When the external pulse wave sensor  110  is determined to be connected, the external pulse wave sensor  110  receives the electric signal; and starts measuring a pulse wave (step S 16 ). 
         [0053]    In the meantime, when the external pulse wave sensor  110  is determined not to be connected, the light-emitting element control section  101  stops sending the electric signal to the connector  114  for connecting the light-emitting element  111 , and the light-receiving element control section  102  stops receiving the electric signal from the connector  114  for connecting the light-receiving element  112 . 
         [0054]    Subsequently, the second light-receiving element control section  104  energizes the second light-receiving element  122 , thereby turning on the second light-receiving element  122  (step S 17 ). When preliminary energization is unnecessary at the time of activation of the second light-receiving element  122 , processing pertaining to step S 17  can be omitted. 
         [0055]    The pulse wave measuring device is in a standby mode for a given time in which the operation of the second light-receiving element  122  becomes stable after being energized (step S 18 ). When the second light-receiving element  122  does not need a wait time before achieving stability, processing pertaining to step S 18  may be omitted. 
         [0056]    The second light-emitting element control section  103  sends the electric signal; and tries to cause the second light-emitting element  121  to emit light (step S 19 ). By means of reaction of the second light-receiving element  122  caused after emission of light from the second light-emitting element  121 , the internal pulse wave sensor attachment determination section  107  determines whether or not the pulse wave measuring device main unit  100  is properly attached (step S 20 ). 
         [0057]    After confirming that the pulse wave measuring unit is attached to the main unit, the internal pulse wave sensor  120  measures a pulse wave (step S 21 ). 
         [0058]    (Determination as to the Connection-and-Attachment of the External Pulse Wave Sensor) 
         [0059]    Next, processing operation of the external pulse wave sensor connection determination section  105  and processing operation of the external pulse wave sensor attachment determination section  106  (step S 15  and the like) will be described in detail along a flowchart shown in  FIG. 7 . 
         [0060]    After emitting of the light-emitting element  111  (step S 30 ), the pulse wave measuring device waits a period of a given sampling cycle (steps S 31  and S 32 ). When sampling timing comes, an output from the light-receiving element  112  is sampled (step S 33 ). At this time, a determination is made as to whether or not the external pulse wave sensor  110  is connected and whether or not the external pulse wave sensor  110  is put on the human body (chiefly on the thick of the finger) of the user, in accordance with a change in the output from the light-receiving element  112  immediately after emitting of the light-emitting element  111 . 
         [0061]    First, a determination is made as to whether or not a value determined by sampling the output from the light-receiving element  111  is equal to or smaller than a given threshold value (e.g., a value of 200) (step S 34 ). 
         [0062]    When the sampled value is equal to or smaller than the threshold value, the number of appearances of a value which is equal to or smaller than the threshold value is counted (step S 35 ). A determination is made as to whether or not the sampled value continually remains smaller than the threshold value for a given period of time (step S 36 ). The continuing time is determined by multiplying a count value by a sampling cycle. When the sampled value remains not smaller than the threshold value for a given period of time or longer, the pulse wave measuring device returns to a sampling standby state (step S 31 ). In contrast, when the sampled value continually remains smaller than the threshold value for a given period of time or longer, the external pulse wave sensor  110  is determined to be connected and properly attached to a finger, and the external pulse wave sensor  110  initiates measurement (step S 37 ). 
         [0063]    In the meantime, when the sampled value is determined not to be equal to and smaller than the threshold value in step S 34 , a determination is made as to whether or not the count values that have been equal to and smaller than the threshold value thus far are equal to or less than a given value (e.g., zero or less) (step S 38 ). When a count value is the sum of a given value and one or more (e.g., one or more) is achieved, the external pulse wave sensor  110  is determined to be connected but improperly attached to a finger (step S 39 ). When the count value is a given value or less (e.g., zero or less), the external pulse wave sensor  110  is determined not to be connected (step S 40 ). 
         [0064]    When the external pulse wave sensor  110  is connected but improperly attached to a finger, a notification to the effect is sent to the user. In relation to a notification method, when the pulse wave measuring device is equipped with a liquid-crystal display, the notification is displayed on the display. When the pulse wave measuring device is equipped with a speaker, the notification is provided by means of warning sound or voice. Both the sound and the voice may also be used in combination. Vibrations caused by a vibrator may also be used alone or in combination. 
         [0065]    In order to accurately determine whether or not the external pulse wave sensor is connected and attached, the user preferably stays quiet. Accordingly, the external pulse wave sensor connection determination section  105  may also be equipped with a motion detection section (not shown) for detecting user&#39;s motion. For instance, an acceleration sensor is preferable for the configuration of the motion detection section. When the motion detection section detects user&#39;s motion of a given level or higher in the middle of response observation of the light-receiving element  112 , it is preferable not to make a determination as to connection and carry out the determination again after the motion has become smaller to a given level or less. 
         [0066]    (Determination as to the Connection-and-Attachment of the Internal Pulse Wave Sensor) 
         [0067]    The internal pulse wave sensor attachment determination section  107  performs a determination in the same manner as does the external pulse wave sensor attachment determination section  106 . Processing operation performed for determining whether or not the internal pulse wave sensor is connected and attached (step S 20 , and the like) will be described in detail along a flowchart shown in  FIG. 8 . 
         [0068]    After emitting of the second light-emitting element  121  (step S 50 ), the pulse wave measuring device waits a period of a given sampling cycle (steps S 51  and S 52 ). When sampling timing comes, an output from the second light-receiving element  122  is sampled (step S 53 ). At this time, a determination is made as to whether or not the internal pulse wave sensor  120  is connected and whether or not the internal pulse wave sensor  120  is put on the human body (chiefly on the wrist) of the user, in accordance with a change in the output from the second light-receiving element  122  immediately after emitting of the second light-emitting element  121 . 
         [0069]    First, a determination is made as to whether or not a value determined by sampling the output from the second light-receiving element  121  is smaller than a given threshold value (e.g., a value of 200) (step S 54 ). 
         [0070]    When the sampled value is not equal to or smaller than the threshold value and when a count value achieved where the number of appearances that is equal to or smaller than the threshold value is counted is equal to or greater than the sum of the given value and one, the pulse wave measuring device main unit  100  is determined to be improperly attached (step S 59 ). When the count value that is equal to or smaller than the threshold value is equal to or smaller than the given value (e.g., zero or less), at least one of the second light-emitting element  121  and the second light-receiving element  122  is determined that a failure, a break in a wire, faulty mounting, or the like occurs (step S 60 ), and a notification of the failure etc. is sent to the user. 
         [0071]    In relation to a notification method, when the pulse wave measuring device is equipped with a liquid-crystal display, the notification is displayed on the display. When the pulse wave measuring device is equipped with a speaker, the notification is provided by means of warning sound or voice. Both the display and the speaker may also be used in combination. Vibrations caused by a vibrator may also be used alone or in combination. 
         [0072]    When the sampled value is smaller than the threshold value, the number of appearances of the sampled value that is equal to or smaller than the threshold value is counted (step S 55 ). A determination is made as to whether or not a period of time during which the sampled value is smaller than a threshold value has continued for a given period of time (step S 56 ). The continuing time is determined by multiplying a count value by a sampling cycle. When the period of time is not equal to or longer than the given period of time, processing returns to a sampling standby state (step S 51 ). When the period of time is equal to or longer than the given period of time, the internal pulse wave sensor  120  initiates measurement (step S 57 ). 
         [0073]    (About a Response Characteristic of the Light-Receiving Element) 
         [0074]    There is subsequently described a response characteristic of the light-receiving element achieved after control of emitting of the light-emitting element. 
         [0075]    When the external pulse wave sensor  110  is not connected, an output from the light-receiving element  112  produced after control of emitting of the light-emitting element  111  is as shown in  FIG. 9 . In  FIG. 9 , a horizontal axis represents a time (seconds), and a vertical axis represents a value achieved after analogue-to-digital conversion of an output from the light-receiving element  112 . 
         [0076]    When the external pulse wave sensor  110  is not connected to the pulse wave measuring device main unit, an output from the light-receiving element  112  remains substantially unchanged, and noticeable changes in the output are not observed. 
         [0077]    Next, when the external pulse wave sensor  110  is connected and left in the dark, an output from the light-receiving element  112  produced immediately after control of emitting of the light-emitting element  111  is as shown in  FIG. 10 . This is, for instance, a case where the user measures a pulse wave immediately before going to bed in the night. As shown in  FIG. 10 , a transient response arose regardless of presence/absence of disturbance. Specifically, a great undershoot once arises in the output from the light-receiving element  112  during a period of only one-tenth of a second immediately after ascertainment of connection of the external pulse wave sensor  110 , and the output value then greatly, sharply increases during a period of only one-third of a second. After about one second, the output reaches the maximum value. Subsequently, the output becomes gradually reduced and enters, after about three seconds, a state where no essential variations are present. 
         [0078]    Accordingly, a given threshold value is set for an output value of the light-receiving element  111 . The external pulse wave sensor connection determination section  105  can determine whether or not the external pulse wave sensor  110  is connected, according to whether or not the output value becomes smaller than the threshold value within a given period of time. Depending on a circuit configuration, there is the case where a transient response shown in  FIG. 10  appears upside down. In such a case, a determination is made according to whether or not an output value has surpassed the threshold value. 
         [0079]    When the external pulse wave sensor  110  is not put on a finger and left in the dark, a change in the output from the light-receiving element  112  appears in the same manner as shown in  FIG. 10 . 
         [0080]    When the external pulse wave sensor  110  is connected under a fluorescent lamp, an output from the light-receiving element  112  immediately after control of emitting of the light-emitting element  111  becomes as shown in  FIG. 11 ; for instance, an output obtained in a case where the user connects the external pulse wave sensor  110  under the fluorescent lamp. 
         [0081]    Even under the fluorescent lamp, a transient response arises regardless of presence/absence of disturbance. Specifically, a large undershoot once arises in an output from the light-receiving element  112  during a period of only one-tenth of a second immediately after ascertainment of connection of the external pulse wave sensor  110 ; the output value sharply, greatly increases within a period of only about one-half second; and the output value reaches the maximum value after about one second. Subsequently, the output value is found to gradually decrease. A variation in the output from the light-receiving element  112  acquired when the external pulse wave sensor  110  is not put on the finger and left under the fluorescent lamp appears in the same manner as does in the case shown in  FIG. 11 . 
         [0082]    An output from the light-receiving element  112  achieved when the external pulse wave sensor  110  is properly put on the finger is provided as shown in  FIG. 12 . Even in this case, a transient response arises regardless of presence/absence of disturbance. Specifically, a large undershoot once arises in an output from the light-receiving element  112  during a period of only one-tenth of a second immediately after ascertainment of attachment of the external pulse wave sensor  110 ; the output value sharply, greatly increases within a period of only about one-half second; and the output value reaches the maximum value after about one second. Subsequently, the output value is found to gradually decrease while pulsation is continually performed. 
         [0083]    When the external pulse wave sensor  110  is put on a finger, the external pulse wave sensor  110  remains in close contact with the surface of the skin. Therefore, reflected light originating from the light-emitting element  111  is more intense than that acquired when the sensor is not attached, and a large transient response arises. Moreover, a duration of the transient response is longer than a duration of the transient response achieved when the sensor is not attached, without regard to the presence/absence of disturbance. 
         [0084]    Accordingly, a given threshold value is set for an output value of the light-receiving element  112 , and another threshold value is also set for a given period of time during which the output value becomes smaller than the given threshold value. When a period of time during which the output value becomes smaller than the given threshold value is longer than a given period of time, the external pulse wave sensor attachment determination section  106  determines that the external pulse wave sensor is attached. In contrast, when the period of time is shorter than the given period of time, the external pulse wave sensor attachment determination section  106  determines that the external pulse wave sensor is not attached. 
         [0085]    The same also applies to a response characteristic of the internal pulse wave sensor  120 . 
       Second Embodiment 
       [0086]    The foregoing first embodiment utilizes a transient response of the light-receiving element occurred after activation of the light-emitting element. However, the present invention is not limited to the embodiment. 
         [0087]    A second embodiment utilizes a plurality of observations of a response of the light-receiving element occurred after activation of the light-emitting element; for instance, two observations. Specifically, a response of the light-receiving element occurred after activation of the light-emitting element, a subsequent response of the light-receiving element occurred after deactivation of the light-emitting element, and a response characteristic of the light-receiving element acquired after re-activation of the light-emitting element are observed, whereby a determination can be made as to whether or not the external pulse wave sensor is connected to the pulse wave measuring device. 
         [0088]    Processing operation of a pulse wave measuring device of the second embodiment corresponds to processing operation represented by the flowchart shown in  FIG. 6  to which a flowchart is partially added.  FIG. 13  shows the flowchart to be added. Specifically, the pulse wave measuring device stays in a standby state for a given period of time. For instance, about one-half second, after foregoing processing pertaining to step S 14  (step S 141 ), and the light-emitting element is switched to the OFF state (step S 142 ). Next, after the pulse wave measuring device stays in a standby state for a given period of time; for instance, about one-half second (step S 143 ), the light-emitting element is again switched to the ON state (step S 144 ). Subsequently, processing returns to previously-described step S 15 . 
         [0089]    For instance, a response characteristic of the light-receiving element achieved in the case of the second embodiment becomes as shown in  FIG. 14 . 
         [0090]    In  FIG. 14 , a thick solid line designates a response characteristic achieved when the external pulse wave sensor is connected in the dark but is not properly put on the user&#39;s finger. In  FIG. 14 , a fine solid line designates a response characteristic achieved when the external pulse wave sensor is connected under a fluorescent lamp but is not properly put on the user&#39;s finger. 
         [0091]    In the second embodiment, a change in an analogue-to-digitally converted value is iterated, and hence a determination as to connection-and-attachment of the external pulse wave sensor becomes more accurate. 
         [0092]    The present invention is not limited as-is to the foregoing embodiments and can be embodied in a practical stage while constituent elements are modified within the scope of the gist of the invention. 
         [0093]    Various inventions can be conceived by appropriate combinations of the plurality of constituent elements disclosed in the embodiments. For example, some constituent elements may also be deleted from all of the constituent elements described in the embodiments. In addition, the constituent elements of the different embodiments may also be combined as necessary. 
         [0094]    As described with reference to the embodiment, there is provided a pulse wave measuring device that enables ascertainment of connection and attachment of a pulse wave sensor, which is located outside a main unit of the device, without having a special connection mechanism. 
         [0095]    According to the embodiment, a pulse wave measuring device to be put on a wrist like a wrist watch can detect connection/disconnection of an external pulse wave sensor, which measures a pulse wave outside a main unit, without use of a special mechanism for detecting connection, and hence a connector can be miniaturized.