Patent Publication Number: US-2020300929-A1

Title: Wearable device, electronic watch, magnetic sensor calibration method, and recording medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Japanese Patent Application No. 2019-052244, filed on Mar. 20, 2019, the entire disclosure of which is incorporated by reference herein. 
     FIELD 
     The technical field of the present disclosure relates to a wearable device, an electronic watch, a magnetic sensor calibration method, and a recording medium. 
     BACKGROUND 
     Technology is described, for example, in Unexamined Japanese Patent Application Kokai Publication No. 2005-345389, that enables automatic magnetic sensor calibration by using rotation of a portable terminal device according to a vibrator operation, the magnetic sensor calibration being triggered by the vibrator operation at the time of an incoming call. 
     SUMMARY 
     A wearable device, an electronic watch, a magnetic sensor calibration method, and a recording medium are disclosed in embodiments of the present disclosure. 
     A wearable device that is an aspect of the present disclosure includes: 
     a magnetic sensor; and 
     a processor configured to perform a magnetic sensor calibration of the magnetic sensor and control two or more function modes including a first function mode and a second function mode, wherein 
     the processor
         determines whether a calibratable state exists in which the magnetic sensor is calibratable,   performs discrimination as to which function mode of the two or more function modes is being executed,   performs the magnetic sensor calibration when (i) the function mode being executed is the first function mode and (ii) the calibratable state exists, and   does not perform the magnetic sensor calibration when (i) the function mode being executed is the second function mode or (ii) the calibratable state does not exist.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of this application can be obtained when the following detailed description is considered in conjunction with the following drawings, in which: 
         FIG. 1  is a drawing illustrating an example of functional configuration of an electronic watch according to Embodiment 1; 
         FIG. 2  is a flowchart of automatic calibration processing according to Embodiment 1; 
         FIG. 3  is a flowchart of calibration stoppage processing according to Modified Example 1; 
         FIG. 4  is a flowchart of automatic calibration processing according to Modified Example 2; 
         FIG. 5  is a flowchart of automatic calibration processing according to Embodiment 2; 
         FIG. 6  is a flowchart of automatic calibration processing according to Embodiment 3; and 
         FIG. 7  is a flowchart of automatic calibration processing according to Embodiment 4. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described below with reference to drawings. Components within the drawings that are the same or equivalent are assigned the same reference sign. 
     Embodiment 1 
     A wearable device according to Embodiment 1 is a wristwatch-type electronic watch provided with a magnetic sensor and is worn on an arm of the user via a watchband. 
     As illustrated in  FIG. 1 , as a hardware configuration, an electronic watch  100  according to Embodiment 1 includes a micro-controller  110 , an oscillator circuit  111 , a magnetic sensor  131 , a display unit  132 , an operation unit  133 , a read only memory (ROM)  134 , an acceleration sensor  135 , a tilt sensor  136 , a pressure sensor  137 , and a temperature sensor  138 . 
     The micro-controller  110  is provided with a frequency dividing circuit  112 , a clock circuit  113 , a random-access memory (RAM)  114 , and a control unit  120 . Further, the frequency dividing circuit  112 , the clock circuit  113 , and the RAM  114  are not necessarily arranged within the micro-controller  110  and may be arranged to the exterior of the micro-controller  110 . The oscillator circuit  111  and the ROM  134  are not necessarily provided to the exterior of the micro-controller  110  and may be provided within the micro-controller  110 . 
     The oscillator circuit  111  causes oscillation of an oscillator such as a quartz oscillator to generate and output a prescribed frequency signal, that is, a clock signal. 
     The frequency dividing circuit  112  performs frequency division of the frequency signal input from the oscillator circuit  111  and outputs the divided frequency signal as a signal of the frequency used by the clock circuit  113  and/or the control unit  120 . The frequency of the signal output by the frequency dividing circuit  112  may be varied on the basis of a setting by the control unit  120 . 
     The clock circuit  113  is a clock that measures the present time by counting oscillations of the signal input from the frequency dividing circuit  112 . Further, the clock circuit  113  may include software that changes a value stored in the RAM  114  at every passage of time of a prescribed period, such as each one second, or alternatively, may include dedicated hardware. The time measured by the clock circuit  113  may be an accumulated period after a certain timing, Coordinated Universal Time (UTC), a standard time of a region such as Japan Standard Time (JST), time of a predetermined city (regional time), or the like. The time measured by the clock circuit  113  is not necessarily in year-month-day-hour-minute-second format. In the present embodiment, the oscillator circuit  111 , the frequency dividing circuit  112 , and the clock circuit  113  are included in the clock unit measuring the day and hour. 
     The RAM  114  is volatile memory such as static random-access memory (SRAM), dynamic random-access memory (DRAM), or the like, and a storage unit includes the RAM  114  together with the ROM  134 . The RAM  114  as working memory stores data such as temporary data, various types of setting data, and image data for display by the display unit  132 . In the present embodiment, the term “image data” refers to image data indicating information such as the present time, date, day of the week, and a battery remaining charge. 
     The control unit  120  includes components such as a central processing unit (CPU), performs various types of calculation processing, and performs general control of overall operations of the electronic watch  100 . The control unit  120  reads a control program stored in the ROM  134 , and while using the RAM  114  as working memory, performs control, such as display control and calculation control corresponding to various types of functions of the electronic watch  100 . Moreover, the control unit  120  is provided with a timer function and can measure whether a prescribed period is passed. Further, the control unit  120  has a multi-thread function and can perform parallel execution of multiple threads, that is, flows of different processing procedures. 
     The magnetic sensor  131  is a sensor that measures magnitude and direction of the magnetic field along three axes. A magneto-resistive element (MR element), for example, is used as an element for sensing the magnetic field. The values measured by the magnetic sensor  131  are output to the micro-controller  110 . 
     The display unit  132  displays data on the time and/or various types of functions. In the present embodiment, the display unit  132  is provided with a liquid crystal panel for digital display of the time, although such configuration is not limiting. For example, the display unit  132  may be provided with a second hand, a minute hand, an hour hand, or the like, and may perform analog display of data on the time and/or various types of functions. Moreover, the display unit  132  may be provided with a liquid crystal panel in addition to the second hand, the minute hand, the hour hand, or the like, may perform analog display of the time by use of each of the hands, and may further display on the liquid crystal panel the data on the date-time and/or the various types of functions. 
     The operation unit  133  receives an input operation from a user and thus sends to the micro-controller  110  as an input signal an electrical signal corresponding to the input operation. The operation unit  133 , for example, includes a push-button switch, a winding crown, a bezel, or the like. Alternatively, a touch sensor may be stacked on a display screen of the display unit  132  of the operation unit  133 , and the touch sensor and the display screen may constitute a touch panel. In this case, the touch sensor senses a contact position and/or a way of touching the display, and sends to the micro-controller  110  an operation signal corresponding to the sensed contact position and/or contact mode. 
     The ROM  134  is non-volatile memory such as mask ROM, flash memory, or the like, and together with the RAM  114 , is included in the storage unit. The ROM  134  stores information such as control programs and initial setting data. The control programs stored in the ROM  134  include a program for below-described automatic calibration processing. 
     The acceleration sensor  135  is a sensor that measures acceleration along three axial directions. The acceleration sensor  135  measures acceleration by using, for example, deformation of a piezoelectric element by acceleration. The acceleration sensor  135  outputs the measured value to the micro-controller  110 . By measuring the acceleration, the acceleration sensor  135  can function as a movement sensor unit due to the ability to sense movement of the electronic watch  100  and the user wearing the electronic watch  100 . 
     The tilt sensor  136  is a sensor that measures tilt of the electronic watch  100 . The tilt sensor  136  can measure the tilt by sensing, for example, gravitational acceleration of the earth. The tilt sensor  136  outputs the measured value to the micro-controller  110 . The tilt sensor  136  also functions as the movement sensor unit for sensing movement of the user wearing the electronic watch  100 . Moreover, the tilt sensor  136  functions also as a tilt measurement unit for sensing the tilt of the electronic watch  100 . 
     The pressure sensor  137  is a sensor that measures pressure of the atmosphere. The pressure sensor  137  measures the air pressure by sensing air pressure by a piezoelectric element, for example. The pressure sensor  137  outputs the measured value to the micro-controller  110 . 
     The temperature sensor  138  is a sensor for measuring heat. In the present embodiment, the temperature sensor  138  measures an air temperature at the periphery of the electronic watch  100 . The temperature sensor  138  measures the air temperature by sensing heat by a thermistor, for example. The temperature sensor  138  outputs the measured value to the micro-controller  110 . 
     Functional configuration of the electronic watch  100  according to Embodiment 1 is described above. Function modes of the electronic watch  100  are described next. 
     The electronic watch  100 , in addition to a time mode for performing the normal display of time, has various types of function modes such as an air pressure measurement mode for measurement of the air pressure, a temperature measurement mode for measuring the air temperature, an azimuth measurement mode for measuring azimuth, an altitude measurement mode for measuring altitude, a sunrise-sunset mode for display of the time of sunrise and/or sunset, a stopwatch mode for timing, a timer mode for sounding an alarm after measurement of passage of a set period, an alarm-setting mode for setting the alarm, and a world-time mode for display of UTC or the time in various cities of the world. 
     The electronic watch  100  runs in various function modes, that is, shifts to a function mode, based on operation of the operation unit  133  by the user. In the case of operation in a function mode other than the time mode, the stopwatch mode, the timer mode, or the world-time mode, upon passage of a determined period thereafter (such as 1 minute or 1 hour, differing in accordance with the function mode) without further user operation, the electronic watch  100  may automatically return to the time mode. These function modes are executed (selected) based on user operation of the operation unit  133  or the like by the control unit  120 , and thus the control unit  120  can perform discrimination as to which function mode is presently being run. Therefore, the control unit  120  functions as a discrimination means for performing discrimination as to which function mode is presently being run. 
     The time mode is a function mode for display of the present time on the display unit  132  and is the normal function used when the electronic watch  100  is being used as a regular watch. Upon starting up the electronic watch  100 , the electronic watch  100  starts operation in the time mode as the default setting of the function mode. 
     The air pressure measurement mode is the function mode that uses the pressure sensor  137  to measure the air pressure and display such pressure on the display unit  132 . In the air pressure measurement mode, the electronic watch  100  measures and displays the air pressure at intervals such as every one minute. Moreover, upon passage of one hour without any further operation by the user, the function mode returns to the time mode. 
     The temperature measurement mode is the function mode that measures the air temperature using the temperature sensor  138  and displays such temperature on the display unit  132 . In the temperature measurement mode, the electronic watch  100  measures and displays the air temperature at intervals such as every one minute. Moreover, upon passage of one hour without any further operation by the user, the function mode returns to the time mode. 
     The azimuth measurement mode is the function mode that measures the geomagnetic field by the magnetic sensor  131  and performs compass-like display of north-based azimuth on the display unit  132 . In the azimuth measurement mode, the electronic watch  100  measures an azimuth and displays the north-based azimuth at intervals such as every one second. Moreover, upon passage of one minute without further operation by the user, the function mode returns to the time mode. 
     The altitude measurement mode is the function mode that uses the pressure sensor  137  to measure the air pressure, converts a change in air pressure to a present value of the altitude, and displays the altitude on the display unit  132 . In the altitude measurement mode, the electronic watch  100  measures air pressure and displays the altitude at intervals such as every one hour. Moreover, upon passage of one hour without further operation by the user, the function mode returns to the time mode. 
     The sunrise-sunset mode is the function mode that calculates the times of sunrise and sunset based on a specific date (year, month, and day) and specific location (latitude and longitude), and displays such times on the display unit  132 . In the sunrise-sunset mode, after the electronic watch  100  displays the sunrise and sunset times, for example, upon passage of one minute without further operation by the user, the function mode returns to the time mode. 
     The stopwatch mode is the function mode that measures the time in 1/100 th  of a second units after pressing of a start button until pressing of a stop button via the operation unit  133 , and that displays such time on the display unit  132 . In the stopwatch mode, even without further operation by the user for a long period, the function mode remains in the stopwatch mode without returning to the time mode. 
     The timer mode is the function mode in which, upon setting of a measurement period by use of the operation unit  133  and pressing of the start button, time is measured until passage of the set period, remaining time is displayed on the display unit  132 , and a sound is sounded to provide notification of expiration of the set period. In the timer mode, even without further operation by the user for a long period, the function mode remains in the timer mode without returning to the time mode. 
     The alarm-setting mode is the function mode for setting an alarm time. In the alarm-setting mode, upon passage of a lengthy time interval such as 5 minutes without further operation by the user, the function mode returns to the time mode. 
     The world-time mode is the function mode in which UTC or the time of various world cities is displayed on the display unit  132 . The user can use the operation unit  133  to specify a city whose time or UTC is to be displayed. In the world-time mode, even without further operation by the user for a lengthy time interval, the function mode remains the world-time mode without returning to the time mode. 
     Although various types of modes are included in the function modes as described above, transition to a function mode other than the time mode does not occur without the user intentionally executing (selecting) such a function mode. That is to say, the running (selecting) of the function mode can be understood to be due to the user wanting to use the function mode. Conversely, the time mode can be understood to be a function mode that is run irrespective of the intention of the user, although the user can intentionally run (select) the time mode, and such running may be, for example, due to a default setting, passage of time, or the like. Thus, the time mode is also termed the default mode, and the function modes other than the time function mode are collectively termed the non-default modes. 
     In the aforementioned azimuth measurement mode, the electronic watch  100  displays, on the display unit  132 , the north-based azimuth on the basis of the measurement value of the magnetic sensor  131 . However, when a component within the electronic watch  100  is magnetized (magnetic), the magnetic sensor  131  measures a sum of the geomagnetic field and magnetic field of the magnetized component, and thus the north-based azimuth cannot be correctly displayed. In this case, the magnetic field of the magnetized component is an offset magnetic field applied to each of the three axial directions of the magnetic sensor  131 . Therefore, the correct geomagnetic field can be measured by measuring this offset magnetic field, and then subtracting this offset magnetic field from the measured values of the magnetic sensor  131 . 
     The offset magnetic field is the magnetic field due to the component fixed within the electronic watch  100 , and thus has a fixed magnitude in each of the three axial directions. Therefore, by measuring the geomagnetic field by the magnetic sensor  131  in various attitudes of the electronic watch  100  such that the direction of the geomagnetic field differs relative to the three axial directions as viewed from the electronic watch  100 , the control unit  120  can find the offset magnetic field from a value of average deviation from the geomagnetic field. The finding of the offset magnetic field is termed the calibration of the magnetic sensor  131 . During performance of the calibration of the magnetic sensor  131 , the control unit  120  functions as a calibration means. 
     By the user performing a certain operation, such as operation of the winding crown in the azimuth measurement mode, the electronic watch  100  enters a mode for a manual calibration of the magnetic sensor  131 , that is, enters a manual calibration mode. The user can perform the manual calibration of the magnetic sensor  131  by an action such as rotation of the electronic watch  100  in this mode. However, such manual calibration is rarely performed by some user due to effort of the user to cause running of the manual calibration mode, and effort such as rotation of the electronic watch  100  thereafter. Thus, measurement of azimuth in the azimuth measurement mode is sometimes performed incorrectly by the electronic watch  100  of the user who does not frequency perform the manual calibration. 
     However, when the user wearing the electronic watch  100  on the arm is moving (movement state), for example, by walking, the magnetic sensor  131  can measure the magnetic field in various directions due to movement such as swinging of the arm of the user. That is to say, when the user is walking, the electronic watch  100  can perform the calibration of the magnetic sensor  131 . Moreover, by sensing movement by the acceleration sensor  135 , the electronic watch  100  can determine whether the user wearing the electronic watch  100  is presently walking. Therefore, the calibration of the magnetic sensor  131  can be performed automatically by sensing of walking of the user. 
     This automatic calibration processing is described with reference to  FIG. 2 . The automatic calibration processing is processing for automatically performing the calibration of the magnetic sensor  131  by the electronic watch  100 , and upon startup of the electronic watch  100 , the electronic watch  100  starts execution of such processing in parallel with other processing, such as time measurement processing to measure the date and time. 
     Firstly, the control unit  120  of the electronic watch  100  determines whether at least 24 hours is passed after the previous calibration of the magnetic sensor  131 , including both automatic calibrations and manual calibrations (step S 101 ). The 24 hour period here is one example of the passed period, and a shorter period such as three hours may be used if the magnetic sensor  131  is to be set as accurately as possible, or alternatively, a long period such as 72 hours may be used in order to suppress power consumption of the electronic watch  100 . 
     When 24 hours is not passed (NO in step S 101 ), processing returns to step S 101 . Such operation is used since, when 24 hours is not passed, the calibration is considered to still be omittable. When at least 24 hours is passed (YES in step S 101 ), the control unit  120  determines, based on measurement of acceleration by the acceleration sensor  135 , whether walking by the user wearing the electronic watch  100  on the arm is sensed (step S 102 ). The algorithm for sensing walking by the acceleration sensor  135  is known technology. For example, walking can be sensed by detecting whether or not periodic peaks occur in values measured by the acceleration sensor  135 . Step S 102  is also termed a sensing step. If walking is not sensed (NO in step S 102 ), processing returns to step S 101 . In the present embodiment, due to the performance of the calibration on the basis of swinging of the arm during walking, the automatic calibration is not performed unless walking is in progress. 
     If walking is sensed (YES in step S 102 ), the control unit  120  determines whether a period in which walking continues to be sensed is equal to or greater than a walking standard period such as 60 seconds (step S 103 ). If the period of continuation of walking is less than the walking standard period (NO in step S 103 ), processing returns to step S 101 . Such a configuration is used since, if the period of continuation is less than the walking standard period, continuation of walking in the future is uncertain, and failure of the automatic calibration that is in progress may occur if walking does not continue. Step S 103  is also termed the determination step since determination is made in step S 103  as to whether the state of movement (walking) sensed in step S 102  is the calibratable state in which the calibration of the magnetic sensor  131  can be performed. 
     If the period of continuation of walking is equal to or greater than the walking standard period (YES in step S 103 ), the control unit  120  determines whether the present function mode of the electronic watch  100  is the time mode (step S 104 ). Step S 104  is also termed the discrimination step. If the time mode is not in progress (NO in step S 104 ), processing returns to step S 101 . Such configuration is used since, if the function mode is not the time mode, the user is considered to be deliberately setting the present function mode, and convenience for the user may be lost by performing the calibration of the magnetic sensor  131  in such a case without permission. 
     If the present function mode of the electronic watch  100  is the time mode (YES in step S 104 ), the control unit  120  turns the magnetic sensor  131  ON and executes the automatic calibration (step S 105 ), and processing returns to step S 101 . In step S 105 , the calibration is performed by using various changes of the direction of the magnetic sensor  131  due to swinging of the arm of the user during walking. Step S 105  is also termed a calibration step. 
     The automatic calibration processing is described above. Even without the user manually performing the calibration in accordance with the aforementioned automatic calibration processing, the electronic watch  100  senses movement of the user, and if the state of such movement is the walking state, the calibration is performed automatically. Therefore, the electronic watch  100  can perform the calibration of the magnetic sensor  131  without imposing a burden on the user. Furthermore, the walking state can be understood to be a state in which the calibration of the magnetic sensor  131  is possible, and thus may also be termed the calibratable state. 
     Moreover, the calibration in accordance with such automatic calibration processing is performed only when the present function mode of the electronic watch  100  is the time mode (default mode), thereby enabling avoidance of termination of the function A by the automatic calibration without user permission when the user is using another function such as a function A. 
     Moreover, rather than performing the calibration only after sensing walking, the electronic watch  100  performs the calibration after recognizing that walking continues for a certain period (walking standard period), and thus such configuration can prevent performance of the calibration when, for example, walking is performed for a few steps in a house, that is, when walking is soon to stop. When the walking soon stops, the swinging of the arm stops prior to completion of the calibration, the calibration cannot be completed, the calibration is performed with low accuracy, or the like; however, the electronic watch  100  can decrease the possibility of lowering of the accuracy or the possibility of failure of the calibration, by performance of the calibration after determination that the period of continuation of walking is equal to or greater than the walking standard period. Due to such configuration, the calibration seldom ends in failure, and power consumption can be suppressed. Further, although in the above embodiment the calibration is to be performed after confirming that the user is continuing to walk, such configuration is not limiting. For example, the calibration may be performed after confirming that the user is continuing to drive a car. 
     Japanese Patent Application Kokai Publication No. 2005-345389 describes technology that enables the automatic magnetic sensor calibration. However, when using the technology described in Japanese Patent Application Kokai Publication No. 2005-345389, sometimes the calibration fails without obtaining data to be acquired in cases such as when rotational movement of the portable terminal device does not continue. In such cases, a problem arises from the standpoint of power consumption in that the calibration operation is wasted. However, according to the aforementioned embodiment, failure of the calibration and lowering of accuracy can be decreased, thereby enabling a lessening in the occurrence of failed calibrations and enabling suppression of power consumption. 
     Modified Example 1 
     In Embodiment 1, automatic calibration processing is executed only when the function mode of the electronic watch  100  is the time mode, that is, the default mode. Such configuration is used since, when the function mode is a non-default mode such as a function A mode that is not the time mode, the function A mode is considered to be deliberately executed by the user since running of the function A mode is desired by the user, and when the calibration is performed in such a case, the function A mode is terminated contrary to the intention of the user. 
     However, when the user causes running of a non-default mode (function mode, such as the function A mode that is other than the time mode) during the calibration, the user is thought to often stop (stop walking) to check the display operating in the function A mode and to look at the display unit  132 . When such action occurs, swinging of the arm stops, and the calibration that is being performed at that time is anticipated to fail. The continuation of the calibration that is anticipated to fail is undesirable from the standpoint of power consumption. Therefore, Modified Example 1 is described below in which the calibration is halted in the case in which the user executes the non-default mode, that is, the function mode other than the time mode, during the calibration. 
     Functional configuration of the electronic watch  100  according to Modified Example 1 is the same as that of the electronic watch  100  according to Embodiment 1 and is illustrated in  FIG. 1 . The electronic watch  100  according to Modified Example 1 differs from the electronic watch  100  according to Embodiment 1 in that, in addition to the automatic calibration processing ( FIG. 2 ), in the Modified Example 1 processing for halting the calibration (calibration stoppage processing) is executed when the function mode is observed to change during execution of the calibration and thus the user executes the non-default mode, that is, the function mode other than the time mode. This calibration stoppage processing is described with reference to  FIG. 3 . Such processing starts in parallel with execution of other processing such as the time measurement processing upon start-up of the electronic watch  100  according to the Modified Example 1. 
     Firstly, the control unit  120  of the electronic watch  101  determines whether the calibration of the magnetic sensor  131  is starting (step S 151 ). For example, if the calibration is starting regardless of whether the calibration is the manual calibration or the automatic calibration, a flag variable indicating that the calibration is in progress is set to “1”, and when the calibration ends, the flag variable is set to “0”, and thus the control unit  120  can, by checking the flag variable, determine whether the calibration is started. If the calibration is not starting (NO in step S 151 ), processing returns to step S 151 . 
     If the calibration is starting (YES in step S 151 ), the control unit  120  determines whether the calibration of the magnetic sensor  131  is finished (step S 152 ). Such determination can be performed by processing similar to that of step S 151 . If the calibration is completed (YES in step S 152 ), processing returns to step S 151 . 
     If the calibration is not completed (NO in step S 152 ), the control unit  120  determines whether a non-default mode, that is, a function mode other than the time mode, is executed (step S 153 ). Such determination can be performed by sensing whether the user is operating the operation unit  133  so that the non-default mode, that is, the function mode other than the time mode, is executed. If the non-default mode (function mode other than the time mode) is not being executed (NO in step S 153 ), processing returns to step S 152 . 
     If the non-default mode (function mode other than the time mode) is executed (YES in step S 153 ), the control unit  120  turns the magnetic sensor  131  OFF to stop the calibration (step S 154 ). Then processing returns to step S 151 . 
     Due to the aforementioned calibration stoppage processing ( FIG. 3 ), when the user executes the non-default mode (function mode other than the time mode), the electronic watch  100  stops the calibration of the magnetic sensor  131 , and thus the continuation of the calibration having a high probability of failure is prevented, and power consumption can be decreased. 
     Although upon start-up of the electronic watch  100  according to Modified Example 1, other processing, such as time measurement processing, is described as starting execution in parallel in the aforementioned calibration stoppage processing ( FIG. 3 ), execution start timing is not limited to this configuration. The calibration stoppage processing may be executed when the calibration is executed, regardless of whether the calibration is executed manually or automatically. In this case, the processing of step S 151  can be omitted, or the portion “returns to step S 151 ” mentioned in the aforementioned  FIG. 3  description can be replaced by “ending calibration stoppage processing”. 
     Modified Example 2 
     Although in Embodiment 1 the electronic watch  100 , after 24 hours is passed since the prior calibration, continues the determination of whether the user is walking, the acceleration sensor  135  is used for such determination, and thus a problem occurs in that power required for operation of the acceleration sensor  135  continues to be consumed. Some sort of movement of the user such as walking can be sensed not only by the acceleration sensor  135  but also by the tilt sensor  136 . Power consumption by the tilt sensor  136  is generally lower than that by the acceleration sensor  135 . Therefore, Modified Example 2 is described that uses the acceleration sensor  135  after sensing of a prescribed tilt by the tilt sensor  136 . 
     Functional configuration of the electronic watch  100  according to Modified Example 2 is the same as that of the electronic watch  100  according to Embodiment 1 and illustrated in  FIG. 1 . The electronic watch  100  according to Modified Example 2 differs from the electronic watch  100  according to Embodiment 1 in that, in Modified Example 2 prior to sensing of walking by the acceleration sensor  135  during the automatic calibration processing, firstly the user is detected to be moving by the tilt sensor. The automatic calibration processing according to this Modified Example 2 is described with reference to  FIG. 4 . Upon start-up of the electronic watch  100  according to Modified Example 2, execution of the automatic calibration processing of Modified Example 2 is started in parallel with the other processing, such as the time measurement processing. 
     The automatic calibration processing according to Modified Example 2 ( FIG. 4 ) is processing that appends step S 111  between step S 101  and step S 102  of the automatic calibration processing according to Embodiment 1 ( FIG. 2 ). Therefore, step S 111  is described below. In step S 111 , the control unit  120  determines whether the tilt measured by the tilt sensor  136  is changed from a previously measured tilt. If there is no change (NO in step S 111 ), processing returns to step S 101 . If there is a change (YES in step S 111 ), the control unit  120  uses the acceleration sensor  135  to determine whether walking of the user wearing the electronic watch  100  on the arm is detected (step S 102 ). 
     Except for the aforementioned processing, the automatic calibration processing according to Modified Example 2 is the same as the automatic calibration processing ( FIG. 2 ) according to Embodiment 1, and thus description thereof is omitted. The electronic watch  100  according to Modified Example 2, due to confirmation of whether the user is moving by the tilt sensor  136  prior to sensing of walking by the acceleration sensor  135 , can lessen power consumption. 
     Embodiment 2 
     Although in Embodiment 1 the electronic watch  100  senses walking of the user and then performs the calibration, the timing of the performance of the calibration is not limited to performance upon sensing the walking of the user. Although an act of looking at the electronic watch by the user wearing the electronic watch on the arm is thought to be performed relatively frequently, after such an act, the user normally performs an action of swinging the arm downward. The calibration can be also performed during the act of swinging the arm downward since, like the action of swinging the arm during walking, the act of swinging the arm downward is an act of moving the electronic watch worn on the arm while changing an orientation of the electronic watch. Thus, Embodiment 2 is described below in which execution of the automatic calibration is triggered by the act of looking at the display of the electronic watch. 
     Functional configuration of the electronic watch  101  according to Embodiment 2 is the same as that of the electronic watch  100  according to Embodiment 1 and is illustrated in  FIG. 1 . Moreover, the function modes of the electronic watch  101  according to Embodiment 2 are also the same as the function modes of the electronic watch  100  according to Embodiment 1, and there is no particular difference between the manual calibration functions of the electronic watch  101  according to Embodiment 2 and the manual calibration functions of the electronic watch  100  according to Embodiment 1. However, the automatic calibration processing of the electronic watch  101  according to Embodiment 2 is different from the automatic calibration processing of the electronic watch  100  according to Embodiment 1 ( FIG. 2 ), and thus the automatic calibration processing of the electronic watch  101  is described below with reference to  FIG. 5 . Upon start-up of the electronic watch  101 , execution of this automatic calibration processing starts in parallel with other processing, such as time measurement processing. 
     Firstly, the control unit  120  of the electronic watch  101  determines whether at least 24 hours is passed after the previous calibration of the magnetic sensor  131 , regardless of whether the previous calibration is the manual calibration or the automatic calibration, (step S 201 ). In the same manner as in Embodiment 1, the setting of the passed period to 24 hours is an example; a shorter period, such as 3 hours, may be used if the magnetic sensor  131  is to be as accurate as possible; and a longer period, such as 72 hours, may be used if suppression of power consumption of the electronic watch  101  is desired. 
     If 24 hours is not passed (NO in step S 201 ), processing returns to step S 201 . Such configuration is used since not performing the calibration is considered to still be permissible if 24 hours is not passed. If at least 24 hours is passed (YES in step S 201 ), the control unit  120  determines whether the user wearing the electronic watch  101  on the arm performs the act of looking at the electronic watch  101  (display unit  132 ) by using the change of acceleration according to the acceleration sensor  135 , the tilt of the electronic watch  101  according to the tilt sensor  136 , or both the change in acceleration according to the acceleration sensor  135  and the tilt of the electronic watch  101  according to the tilt sensor  136  (step S 202 ). Whether the user performs the act of looking at the electronic watch  101  (display unit  132 ) can be determined on the basis of (i) a change in acceleration of the part where the user wears the electronic watch  101  when the user is performing the act of looking at the display unit  132  of the electronic watch  101  from the state in which the arm is naturally swung downward, (ii) tilt of the electronic watch  101  when the user looks at the display unit  132 , or the like. If the act of looking at the electronic watch  101  (display unit  132 ) is not being performed (NO in step S 202 ), processing returns to step S 201 . Since the calibration is performed based on swinging of the arm after the act of looking at the electronic watch  101  (display unit  132 ) in the present embodiment, the automatic calibration is not performed unless the act of looking at the electronic watch  101  (display unit  132 ) is performed. 
     If the act of looking at the electronic watch  101  (display unit  132 ) is performed (YES in step S 202 ), the control unit  120  uses the acceleration sensor  135  to determine whether the stationary state of the electronic watch  101  is continuing (step S 203 ). If the stationary state of the electronic watch  101  is continuing (YES in step S 203 ), processing returns to step S 203 . Such configuration is used since the interval while the stationary state continues is thought to be when the user is continuing to look at the electronic watch  101  (display unit  132 ), and the swinging movement of the arm is not starting. 
     If the stationary state of the electronic watch  101  is not continuing (NO in step S 203 ), the control unit  120  determines whether the present function mode of the electronic watch  101  is the time mode (step S 204 ). If the present function mode is not the time mode (NO in step S 204 ), processing returns to step S 201 . Such configuration is used since, if the present function mode is not the time mode, the user is considered to be deliberately setting the present function mode, and convenience for the user may be lost by performing the calibration of the magnetic sensor  131  in such a case without permission. 
     If the present function mode of the electronic watch  101  is the time mode (YES in step S 204 ), the control unit  120  turns the magnetic sensor  131  ON and executes the automatic calibration (step S 205 ), and processing returns to step S 201 . In step S 205 , the calibration is performed using the change of the orientation of the magnetic sensor  131  to various directions due to the act of downward swinging of the arm previously raised in order for the user to look at the electronic watch  101  (display unit  132 ). That is, the calibration is performed by the electronic watch  101  after determining whether the user performs the act of looking at the electronic watch  101 . Such configuration enables reliable use of timing of the change of the orientation of the magnetic sensor  131  to various directions due to swinging downward of the arm that is previously raised for the user to then look at the electronic watch  101 , thereby decreasing the possibility of the failure of the calibration or the possibility of the low accuracy of the calibration. Such configuration decreases the frequency of calibrations that end in failure and enables suppression of power consumption. 
     The automatic calibration processing according to Embodiment 2 is described above. Due to the aforementioned automatic calibration processing, even without the user performing the manual calibration, the electronic watch  101  senses the movement of the user, and if the state of such movement is the operational state in which the electronic watch  101  is looked at, performs the calibration automatically. Therefore, the electronic watch  101  can perform the calibration of the magnetic sensor  131  without imposing a burden on the user. Further, the operational state in which the electronic watch  101  is looked at can be understood to be a state in which the calibration of the magnetic sensor  131  is possible, and thus this state may also be termed the calibratable state. 
     Moreover, this calibration is performed only when the present function mode of the electronic watch  101  is the time mode, and thus by the performance of the calibration automatically when the user is using another function such as the function A, termination of the function A without permission can be avoided. 
     Embodiment 3 
     Another timing may be considered for the performance of the calibration. For example, the timing may be a timing at which, after the electronic watch is in a state of static placement on a desk, the user then takes up the electronic watch and attaches the electronic watch to the arm. According to such timing, the electronic watch taken up by the user moves while the orientation of the electronic watch changes until the electronic watch is attached to the arm, and thus the calibration can be performed. Thus Embodiment 3 is described below in which the calibration is performed automatically at the timing of attachment to the arm. 
     Functional configuration of the electronic watch  102  according to Embodiment 3 is the same as that of the electronic watch  100  according to Embodiment 1, and is illustrated in  FIG. 1 . Moreover, the function modes of the electronic watch  102  according to Embodiment 3 are the same as the function modes of the electronic watch  100  according to Embodiment 1, and there is no particular difference in the manual calibration function of the electronic watch  102  according to Embodiment 3 versus the electronic watch  100  according to the Embodiment 1. However, the automatic calibration processing of the electronic watch  102  according to Embodiment 3 differs from the automatic calibration processing of the electronic watch  100  according to Embodiment 1 ( FIG. 2 ), and thus the automatic calibration processing of the electronic watch  102  is described below with reference to  FIG. 6 . Upon start-up of the electronic watch  102 , execution of the automatic calibration processing of Embodiment 3 starts in parallel to other processing such as time measurement processing. 
     Firstly, the control unit  120  of the electronic watch  102  determines whether a time (stand-still continuation period) during which the electronic watch  102  continues to stand still is equal to or greater than a stand-still standard period, such as 3 hours or more, by using the change in acceleration according to the acceleration sensor  135 , the change in tilt according to the tilt sensor  136 , or both the change in acceleration according to the acceleration sensor  135  and change in tilt according to the tilt sensor  136  (step S 301 ). If the stand-still continuation period is less than the stand-still standard period (NO in step S 301 ), processing returns to step S 301 . 
     If the stand-still continuation period is equal to or greater than the stand-still standard period (YES in step S 301 ), the control unit  120  determines whether the electronic watch  102  is moved, that is, whether a position or orientation of the electronic watch  102  changes, by using the change in acceleration according to the acceleration sensor  135 , the change in tilt according to the tilt sensor  136 , or both the change in acceleration according to the acceleration sensor  135  and change in tilt according to the tilt sensor  136  (step S 302 ). If the electronic watch  102  does not move, that is, the position or orientation of the electronic watch  102  does not change (NO in step S 302 ), processing returns to step S 301 . 
     If the electronic watch  102  is moved, that is, in position or orientation of the electronic watch  102  changes (YES in step S 302 ), the control unit  120  determines whether at least 24 hours is passed after the previous calibration of the magnetic sensor  131 , regardless of whether the previous calibration is the manual calibration or the automatic calibration, (step S 303 ). In the same manner as in Embodiment 1, the setting of the passed period to 24 hours is an example; a shorter period, such as 3 hours, may be used if the magnetic sensor  131  is to be as accurate as possible; and a longer period, such as 72 hours, may be used if suppression of power consumption of the electronic watch  102  is desired. 
     If 24 hours is not passed (NO in step S 303 ), processing returns to step S 301 . Such configuration is used since, if 24 hours is not passed, omission of the calibration still is considered to be permissible. If at least 24 hours is passed (YES in step S 303 ), the control unit  120  determines whether the present function mode of the electronic watch  102  is the time mode (step S 304 ). If the present function mode is not the time mode (NO in step S 304 ), processing returns to step S 301 . Such configuration is used since, if the present function mode is not the time mode, the user is considered to be deliberately performing setting to the present function mode, and when the calibration of the magnetic sensor  131  is performed without permission in this case, convenience for the user may be lost. 
     When the present function mode of the electronic watch  102  is the time mode (YES in step S 304 ), the control unit  120  turns the magnetic sensor  131  ON and executes the automatic calibration (step S 305 ), and processing returns to step S 301 . In step S 305 , the calibration is performed using the change of the orientation of the magnetic sensor  131  to various directions due to movement when the electronic watch  102  is attached to the arm by the user. That is to say, the electronic watch  102  performs the calibration after determining that the electronic watch  102  is moved due to the user attaching the electronic watch  102  to the arm. Due to such configuration, after movement such as the user attaching the electronic watch  102  to the arm, the timing of the change of the orientation of the magnetic sensor  131  to various directions can be reliability used, thereby enabling lowering of the possibility of failure of the calibration, the possibility of lowering of accuracy, or the like. Thus, the calibration seldom ends in failure, and power consumption can be suppressed. 
     The automatic calibration processing according to Embodiment 3 is described above. Due to the aforementioned automatic calibration processing, even when the user does not perform the calibration manually, the electronic watch  102  senses movement of the user and performs the calibration automatically if the state of such movement is the operational state in which the electronic watch  102  is attached to the arm. Therefore, the electronic watch  102  can perform the calibration of the magnetic sensor  131  without imposing a burden on the user. Further, the operational state in which the electronic watch  102  is attached to the arm can be understood to be a state in which the calibration of the magnetic sensor  131  is possible, and thus this state may also be termed the calibratable state. 
     Moreover, this calibration is only performed when the present function mode of the electronic watch  102  is the time mode, and thus when the user is using another function, such as the function A, the automatic calibration can be performed, thereby avoiding termination of the function A without permission. 
     Embodiment 4 
     Another timing may be considered for the performance of the calibration. For example, the timing may be a timing at which the user removes the watchband of the electronic watch. According to such timing, the calibration can be performed since the electronic watch is moved while changing the orientation of the electronic watch until the user places the electronic watch on a desk or the like after releasing the watchband of the electronic watch and removing the electronic watch from the arm. Thus Embodiment 4 is described below in which execution of the automatic calibration is triggered by an act of releasing the watchband of the electronic watch by the user. 
     Functional configuration of the electronic watch  103  according to Embodiment 4 is the same as that of the electronic watch  100  according to Embodiment 1, and is illustrated in  FIG. 1 . Moreover, the function modes of the electronic watch  103  according to Embodiment 4 are the same as the function modes of the electronic watch  100  according to Embodiment 1, and there is no particular difference between the manual calibration function of the electronic watch  103  according to Embodiment 4 and the manual calibration of the electronic watch  100  according to the Embodiment 1. However, the automatic calibration processing of the electronic watch  103  according to Embodiment 4 differs from the automatic calibration processing of the electronic watch  100  according to Embodiment 1 ( FIG. 2 ), and thus the automatic calibration processing of the electronic watch  103  is described below with reference to  FIG. 7 . Upon start-up of the electronic watch  103 , execution of the automatic calibration processing of Embodiment 4 starts in parallel with other processing such as time measurement processing. 
     Firstly, the control unit  120  of the electronic watch  103  determines whether at least 24 hours is passed after the previous calibration of the magnetic sensor  131  regardless of whether the previous calibration is the manual calibration or the automatic calibration (step S 401 ). In the same manner as in Embodiment 1, the setting of the passed period to 24 hours is an example; a shorter period, such as 3 hours, may be used if the magnetic sensor  131  is to be as accurate as possible; and a longer period, such as 72 hours, may be used if suppression of power consumption of the electronic watch  103  is desired. 
     If 24 hours is not passed (NO in step S 401 ), processing returns to step S 401 . Such configuration is used since not performing the calibration is considered to still be permissible if 24 hours is not passed. If at least 24 hours is passed (YES in step S 401 ), the control unit  120  determines whether the user wearing the electronic watch  103  on the arm performs the act of removing the watchband of the electronic watch  103 , by using the change in acceleration according to the acceleration sensor  135 , the tilt of the electronic watch  103  according to the tilt sensor  136 , or both the change in acceleration according to the acceleration sensor  135  and the tilt of the electronic watch  103  according to the tilt sensor  136  (step S 402 ). 
     Due to performing an act of rotating the wrist that is characteristic of the release of the watchband when the user releases the watchband of the electronic watch  103 , the control unit  120  can determine in step S 402 , based upon such movement of the wrist or the like, whether the watchband is previously removed by the user. Moreover, the watchband part of the electronic watch  103  may be provided with a watchband attachment sensor that is capable of sensing attachment and removal of the watchband. If the electronic watch  103  is provided with the watchband attachment sensor, the control unit  120  can determine, by a result of sensing by the watchband attachment sensor, whether the watchband is removed. 
     If the watchband is not removed (NO in step S 402 ), processing returns to step S 401 . In the present embodiment, the calibration is performed on the basis of movement of the electronic watch  103  after removal of the electronic watch  103 , and therefore the automatic calibration is not performed unless the act of removing the electronic watch  103  is performed. 
     If the watchband is removed (YES in step S 402 ), the control unit  120  determines whether the present function mode of the electronic watch  103  is the time mode (step S 403 ). If the present function mode is not the time mode (NO in step S 403 ), processing returns to step S 401 . Such configuration is used since, if the present function mode is not the time mode, the user is considered to be deliberately performing setting to the present function mode, and when the calibration of the magnetic sensor  131  is performed without permission in this case, convenience for the user may be lost. However, after removal of the watchband, the user is considered not to use the electronic watch  103  until attachment is repeated, and thus the processing of step S 403  may be omitted. 
     When the processing of step S 403  is not omitted, if the present function mode of the electronic watch  103  is the time mode in step S 403  (YES in step S 403 ), the control unit  120  turns the magnetic sensor  131  ON and executes the automatic calibration processing (step S 404 ), and processing returns to step S 401 . In step S 404 , the calibration is performed using the change of the orientation of the magnetic sensor  131  to various directions due to the act of the user taking the electronic watch  103  from the arm and placing the electronic watch  103  on the desk or the like by the user. That is to say, the electronic watch  103  performs the calibration after determining that the electronic watch  103  is removed from the arm. Due to such configuration, after placement of the electronic watch  103  on the desk or the like by the user, the timing of the change of the orientation of the magnetic sensor  131  to various directions can be reliability used, thereby enabling lowering of the possibility of failure of the calibration, the possibility of lowering of accuracy, or the like. Thus, the calibration seldom ends in failure, and power consumption can be suppressed. 
     The automatic calibration processing according to Embodiment 4 is described above. Due to the aforementioned automatic calibration processing, even without the user performing the manual calibration, the electronic watch  103  senses movement of the user, and if the state of such movement is the operational state of removing the electronic watch  103  from the arm, the calibration is performed automatically. Therefore, the electronic watch  103  can perform the calibration of the magnetic sensor  131  without imposing a burden on the user. Furthermore, the state in which the electronic watch  103  is removed from the arm can also be understood to be a state in which the calibration of the magnetic sensor  131  is enabled, and thus may also be termed the calibratable state. 
     Furthermore, the present disclosure is not limited to the aforementioned embodiments, and modifications are possible by variously combining such embodiments. For example, although in the aforementioned embodiments an electronic watch is cited as one example of the wearable device provided with the magnetic sensor, the present disclosure is not limited to the electronic watch, and application is possible to a freely-selected wearable device provided with the magnetic sensor, such as a smartwatch, a physical activity meter, or the like. Although an electronic watch is to be provided with a time-measuring unit for measuring the date and hour, in the case of application to a wearable device that may omit measurement of the date and hour, the time-measuring unit may be omitted from the wearable device. 
     Moreover, combining the automatic calibration processing occurring in the aforementioned embodiments enables an increase in the number of timings of the performance of the automatic magnetic sensor calibration. For example, if Embodiment 1 and Embodiment 2 are combined, the accuracy of the magnetic sensor  131  can be further increased, by performing the automatic calibration not only when the user is walking but also when the act of looking at the display unit  132  is performed. 
     Moreover, for example, by combining Embodiments 2-4 and Modified Example 1, the calibration can be stopped in the case in which the user during the calibration changes the function mode to an function mode other than the time mode (non-default mode) in the electronic watches  101 ,  102 , and  103  according to Embodiments 2-4, and wasteful consumption of power can be prevented. 
     Each of the electronic watches  100 ,  101 ,  102 , and  103  of the aforementioned embodiments is described as being provided with the pressure sensor  137 . However, if the electronic watches  100 ,  101 ,  102 , and  103  are not necessarily provided with the function mode requiring the pressure sensor  137 , such as the air pressure measurement mode and the altitude measurement mode, then the pressure sensor  137  may be omitted from each of the electronic watches  100 ,  101 ,  102 , and  103 . 
     Moreover, Each of the electronic watches  100 ,  101 ,  102 , and  103  of the aforementioned embodiments are described as being provided with the temperature sensor  138 . However, if the electronic watches  100 ,  101 ,  102 , and  103  are not necessarily provided with the function mode requiring the temperature sensor  138 , such as the temperature measurement mode, then the temperature sensor  138  may be omitted from each of the electronic watches  100 ,  101 ,  102 , and  103 . 
     Moreover, for example, sensing walking by sensing the existence of periodic peaks in values measured by the acceleration sensor is described as a method of sensing of walking by the acceleration sensor  135 . However, this method is not limiting, and walking may be sensed by a freely-selected method as long as the method of sensing walking is based on output of the acceleration sensor  135 . 
     Furthermore, the functions of each of the electronic watches  100 ,  101 ,  102 , and  103  can be achieved using a computer such as a portable personal computer (PC). Specifically, a program for automatic calibration processing performed by the electronic watches  100 ,  101 ,  102 , and  103  in the aforementioned embodiments is described as being stored beforehand on the ROM  134 . However, the devices according to the present disclosure may include a computer capable of achieving each of the aforementioned functions by (i) storing the program on a computer-readable storage medium such as a flexible disc, a compact disc read only memory (CD-ROM), a digital versatile disc (DVD), a magneto-optical (MO) disc, a memory card, a universal serial bus (USB) memory, or the like, (ii) distributing the computer-readable storage medium, and (iii) reading and installing the program on the computer. 
     The foregoing describes some example embodiments for explanatory purposes. Although the foregoing discussion has presented specific embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. This detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined only by the included claims, along with the full range of equivalents to which such claims are entitled.