Patent Publication Number: US-11391570-B2

Title: Inertial measurement unit

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-178184, filed Sep. 30, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an inertial measurement unit and the like. 
     2. Related Art 
     Recently, with the increasing precision of manufacturing devices and measuring devices or the like, vibration measurement to improve the efficiency and yield of production processes has become more important. Therefore, simplified device vibration measurement and ambient vibration measurement are desired. For example, JP-A-2016-205868 discloses a vibration monitoring device in which a vibration detection unit detects a vibration, using a vibration sensor, and wirelessly transmits vibration data acquired by the detection, and in which a vibration monitor receives the transmitted vibration data and displays the vibration data at a display unit. In this vibration monitoring device, the vibration detection unit detects a vibration of a device and an ambient vibration, and the detected vibration data can be displayed at the display unit of the vibration monitor provided separately from the vibration detection unit. 
     Using an inertial measurement unit having an inertial sensor such as an acceleration sensor or angular velocity sensor enables the monitoring of the state of a device or the monitoring of the ambient state as described above. However, when using the technique of displaying the result of the measurement by the inertial measurement unit at the display unit provided separately from the inertial measurement unit, as in JP-A-2016-205868, the user needs to check the result of the measurement by looking at the display unit provided separately from the inertial measurement unit. This makes the checking work complicated for the user. Also, since the content of information to be displayed at the display unit based on the detection information from the inertial sensor varies depending on the user using the inertial measurement unit, various demands about the display form of the display information need to be met. 
     SUMMARY 
     An aspect of the present disclosure relates to an inertial measurement unit including: a sensor unit having at least one inertial sensor; a display unit performing a display based on detection information from the inertial sensor; and a mode changeover switch. The mode changeover switch changes a display mode of the display unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a configuration example of an inertial measurement unit according to an embodiment. 
         FIG. 2  is a perspective view showing another configuration example of the inertial measurement unit according to the embodiment. 
         FIG. 3  is an exploded perspective view of the inertial measurement unit. 
         FIG. 4  is a side view of the inertial measurement unit. 
         FIG. 5  is a bottom view of the inertial measurement unit. 
         FIG. 6  is a plan view of a protection plate. 
         FIG. 7  is a plan view of a protection plate. 
         FIG. 8  is a plan view of a display unit. 
         FIG. 9  is an explanatory view of a mode changeover switch, a reset switch, and a measurement start switch. 
         FIG. 10  is an explanatory view showing a changeover of display mode. 
         FIG. 11  is an explanatory view showing a changeover of display mode. 
         FIG. 12  is an explanatory view of a wireless communication unit and an antenna unit. 
         FIG. 13  is an explanatory view showing the coupling between a sensor-side connector and a substrate-side connector. 
         FIG. 14  is a state transition diagram explaining an operation of the inertial measurement unit. 
         FIG. 15  is an exploded perspective view of a first configuration example of a sensor unit. 
         FIG. 16  is an exploded perspective view of a second configuration example of the sensor unit. 
         FIG. 17  is a plan view of a sensor substrate in the second configuration example. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An embodiment will now be described. The embodiment described below does not unduly limit the contents described in the appended claims. Not all the components described in the embodiment are essential components. 
     1. Inertial Measurement Unit 
       FIG. 1  is a perspective view showing a configuration example of an inertial measurement unit  10  according to this embodiment. The inertial measurement unit (IMU)  10  includes a sensor unit  20 . The inertial measurement unit  10  can also include fixing members  11 ,  12 ,  13 , a substrate  40 , a base  150 , and a protection plate  160 . In  FIG. 1 , a direction from the inertial measurement unit  10  toward an installation surface  2  for the inertial measurement unit  10  is defined as a direction DR 1 , and a direction orthogonal to DR 1  is defined as a direction DR 2 . The direction DR 1  is a direction orthogonal to the installation surface  2  and, for example, orthogonal to a main surface of the sensor unit  20 . The main surface is a top surface or bottom surface of the sensor unit  20  and, for example, a surface orthogonal to a lateral surface. A direction DR 3  is a direction orthogonal to the direction DR 1  and the direction DR 2 . Directions DR 4 , DR 5 , DR 6  are the opposite directions of the directions DR 1 , DR 2 , DR 3 , respectively. The directions DR 1 , DR 2 , DR 3 , DR 4 , DR 5 , DR 6  are a first direction, a second direction, a third direction, a fourth direction, a fifth direction, and a sixth direction, respectively. 
     The sensor unit  20  includes at least one inertial sensor. The inertial sensor is a physical quantity sensor detecting physical quantity information. Specifically, as described later with reference to  FIGS. 15, 16, and 17 , the sensor unit  20  includes at least one acceleration sensor, as at least one inertial sensor. Alternatively, the sensor unit  20  includes at least one acceleration sensor and at least one angular velocity sensor, as at least one inertial sensor. The angular velocity sensor is, for example, a gyro sensor. The inertial sensor is not limited to the acceleration sensor or the angular velocity sensor and may be any sensor configured to detect information about inertia by any detection technique. The inertial sensor may be a physical quantity sensor configured to detect a physical quantity equivalent to an acceleration or angular velocity. The inertial sensor may be, for example, a physical quantity sensor configured to detect a physical quantity such as a velocity or angular acceleration. The sensor unit  20  includes a case  24 . For example, the sensor unit  20  includes a sensor substrate  210  provided with at least one inertial sensor, and the case  24  accommodating the sensor substrate  210 , as shown in  FIGS. 15 to 17 , described later. The case  24  is formed of an electrically conductive member such as a metal and is provided with the sensor substrate  210  in an accommodation space inside the case  24 . 
     The substrate  40  is provided with at least one of a processing unit  50  and a display unit  60 . In  FIG. 1 , both of the processing unit  50  and the display unit  60  are provided at the substrate  40 . However, for example, only the processing unit  50  may be provided at the substrate  40 , or only the display unit  60  may be provided at the substrate  40 . The substrate  40  is a circuit board, for example, a printed circuit board where a metal wiring is formed. The substrate  40  is, for example, a rigid substrate. 
     The processing unit  50  performs processing based on detection information from the inertial sensor of the sensor unit  20 . The processing unit  50  is a processing circuit and can be implemented by a processor such as an MPU or CPU. Alternatively, the processing unit  50  may be implemented by an ASIC (application-specific integrated circuit) by automatic placement and routing of a gate array or the like. For example, the processing unit  50  is electrically coupled to the inertial sensor of the sensor unit  20  via a connector or the like, as described later. The detection information from the inertial sensor is inputted to the processing unit  50  via the connector or the like. The detection information is, for example, acceleration information, angular velocity information, or information based on these pieces of information. The processing unit  50  performs various kinds of processing based on the detection information from the inertial sensor. For example, the processing unit  50  performs processing to process the detection information. For example, the processing unit  50  performs processing to process the detection information into information that is appropriate as display information to be displayed at the display unit  60  or at a display unit  70  shown in  FIG. 2 , described later. The processing unit  50  also performs analysis processing to analyze the detection information. For example, the processing unit  50  performs analysis processing to analyze a vibration, tilt, or attitude or the like of a measuring target, based on the detection information from the inertial sensor. For example, the processing unit  50  performs FFT analysis (Fast Fourier Transform analysis) and thus analyzes a frequency component of vibration information or the like, as the analysis processing. 
     The display unit  60  in  FIG. 1  and the display unit in  FIG. 2  perform a display based on the detection information from the inertial sensor of the sensor unit  20 . For example, when the inertial measurement unit  10  has the processing unit  50  and the display units  60 ,  70 , the processing unit  50  performs processing based on the detection information from the inertial sensor, and the display units  60 ,  70  performs a display based on the result of the processing by the processing unit  50 . For example, display information based on the result of the processing on the detection information by the processing unit  50  is displayed at the display units  60 ,  70 . For example, when the processing unit  50  performs processing to process the detection information, the display units  60 ,  70  display display information corresponding to the processed detection information. When the processing unit  50  performs analysis processing to analyze the detection information, the display units  60 ,  70  display display information corresponding to the result of the analysis. For example, in  FIG. 1 , the display unit  60 , which is a display device, has light-emitting element groups  62 ,  64 . The light-emitting element of the light-emitting element groups  62 ,  64  is an element converting an electrical signal into a light signal and can be implemented by a semiconductor element such as a light-emitting diode (LED). Alternatively, the light-emitting element may be implemented by other elements than the semiconductor element. In  FIG. 2 , the display unit  70 , which is a display module, has a display panel  72 . The display panel  72  is, for example, an organic EL panel, liquid crystal panel or the like. 
     The substrate  40  is also provided with a mode changeover switch  80 , a reset switch  82 , and a measurement start switch  84 . The substrate  40  is also provided with a wireless communication unit  90  and an antenna unit  92 . These switches and the wireless communication unit  90  and the like will be described in detail later. 
     The substrate  40  is also provided with an interface unit  100 . The interface unit  100  performs wired communicates with outside. For example, the interface unit  100  implements a communication interface such as UART (universal asynchronous receiver/transmitter), GPIO (general-purpose input/output), or SPI (serial peripheral interface). The UART is an asynchronous serial communication interface. The GPIO is a general-purpose communication interface whose operation can be controlled by the user at the time of execution. The SPI is an interface communicating via three or four signal lines including a serial clock signal line, a serial data signal line and the like. The substrate  40  is also provided with an interface unit  101  implementing a JTAG or similar communication interface. 
     The substrate  40  is also provided with memories  102 ,  103 ,  104 . The memory  102  is, for example, a non-volatile memory and is implemented, for example, by an EEPROM (electrically erasable programmable read-only memory) where data is electrically erasable, or an OTP (one time programmable) memory using a FAMOS (floating-gate avalanche injection MOS) or the like. The memories  103 ,  104  are, for example, SRAMs temporarily storing data. The substrate  40  is also provided with a power interface  106 . External power is supplied to the inertial measurement unit  10  via the power interface  106 . 
     The inertial measurement unit  10  includes the base  150 . The base  150  is a member for installing the inertial measurement unit  10  at the installation surface  2 . For example, the sensor unit  20  is provided between the base  150  and the substrate  40 , and the base  150  is fixed to the sensor unit  20  by the fixing members  11 ,  12 ,  13 , which are at least one fixing member. For example, the base  150  is provided between the sensor unit  20  and the installation surface  2 . The installation surface  2  is, for example, a surface of a device such as a manufacturing device or a measuring device, or a floor surface where the device is installed. The base  150  has a recess  154  at a bottom surface, which is the surface facing the installation surface  2 . In cases such as where the inertial measurement unit  10  is installed at the installation surface  2  via a double-sided adhesive tape, the provision of such a recess  154  can make it easier to strip off the double-sided adhesive tape. The sensor unit  20  is provided in contact with the top surface of the base  150 . 
     The protection plate  160  is a member for protecting the substrate  40 . The substrate  40  is provided between the sensor unit  20  and the protection plate  160 . Thus, the components installed at the substrate  40  such as the processing unit  50 , the display unit  60 , and the wireless communication unit  90  can be protected using the protection plate  160 . For example, the protection plate  160 , which is a first protection plate, is a transparent or semitransparent plate-like member and can be implemented, for example, by a resin plate of acryl or the like. The protection plate  160  may be formed of other materials than acryl. The protection plate  160  may be, for example, a resin plate of ABS or PET, or may be formed of other materials than resin. 
     The inertial measurement unit  10  includes at least one fixing member removably fixing the sensor unit  20  and the substrate  40  together. Specifically, in  FIG. 1 , the inertial measurement unit  10  includes the fixing members  11 ,  12 ,  13  as at least one fixing member. Although the three fixing members  11 ,  12 ,  13  are provided in  FIG. 1 , the number of fixing members may be two or fewer, or four or more. In  FIG. 1 , columnar members are provided as the fixing members  11 ,  12 ,  13 . That is, the fixing members  11 ,  12 ,  13  are columnar members having the longitudinal direction thereof along the direction DR 1 . As described later, the columnar members are provided in such a way as to penetrate holes in the sensor unit  20 , the substrate  40  and the like. 
       FIG. 2  shows another configuration example of the inertial measurement unit  10 . In  FIG. 2 , a substrate  48  is provided in addition to the configuration shown in  FIG. 1 . The substrate  48  is provided with the display unit  70  having the display panel  72 . The display panel  72 , which is an organic EL panel or liquid crystal panel, performs a display based on the detection information from the sensor unit  20 . For example, the processing unit  50  provided at the substrate  40 , which is a first substrate, performs analysis processing to analyze a vibration or the like of a measuring target such as a device or floor surface, based on the detection information from the inertial sensor of the sensor unit  20 . The display unit  70  provided at the substrate  48 , which is a second substrate, displays information about the result of the analysis processing. For example, the display unit  70  displays information about the result of analysis such as FFT on the vibration of the measuring target. The display unit  70  displays, for example, information about a peak frequency or peak value of the vibration. 
     In  FIG. 2 , a protection plate  170  is provided in addition to the protection plate  160 . The protection plate  170  is, for example, a protection member for the substrate  48 . For example, the substrate  48  is provided between the protection plate  160  and the protection plate  170 . Thus, the protection plate  170  and the like installed at the substrate  48  can be protected using the protection plate  170 . For example, the protection plate  170 , which is a second protection plate, is a transparent or semitransparent plate-like member and can be implemented, for example, by a resin plate of acryl or the like. The protection plate  170  as the second protection plate may be formed of other materials than acryl and may be formed of other materials than resin, similarly to the protection plate  160  as the first protection plate. In this way, in  FIG. 2 , the substrate  48  is provided between the protection plate  160  and the protection plate  170 , and the substrate  40  is provided between the sensor unit  20  and the protection plate  160 . 
     The protection plate  170  is provided with a window  174 . At the position of this window  174 , the display unit  70  installed at the substrate  48  is arranged. This enables the user to view the information displayed at the display unit  70 , via the window  174 . 
       FIG. 3  is an exploded perspective view of the inertial measurement unit  10 . As shown in  FIG. 3 , the sensor unit  20  is provided with a plurality of holes  21 ,  22 ,  23 , and the substrate  40  is provided with a plurality of holes  41 ,  42 ,  43 . As the fixing members  11 ,  12 ,  13 , which are columnar members, fit into the plurality of holes  41 ,  42 ,  43  provided in the substrate  40  and the plurality of holes  21 ,  22 ,  23  provided in the sensor unit  20 , the sensor unit  20  and the substrate  40  are removably fixed together. Specifically, the fixing members  11 ,  12 ,  13  are provided in such a way as to penetrate the holes  41 ,  42 ,  43  in the substrate  40  and the holes  21 ,  22 ,  23  in the sensor unit  20 . Also, the base  150  is provided with holes  151 ,  152 ,  153 . As the fixing members  11 ,  12 ,  13 , which are columnar members, fit into the holes  151 ,  152 ,  153  provided in the base  150 , the base  150  is fixed to the sensor unit  20 . Also, the protection plate  160  is provided with a plurality of holes  161 ,  162 ,  163  and the protection plate  170  is provided with a plurality of holes  171 ,  172 ,  173 . As the fixing members  11 ,  12 ,  13  fit into the holes  161 ,  162 ,  163  and the holes  171 ,  172 ,  173 , the protection plates  160 ,  170  are removably fixed together. 
     For example, the fixing members  11 ,  12 ,  13 , which are columnar members, are screw members. That is, the fixing members  11 ,  12 ,  13  are male screws threaded on the outer circumference. The holes  151 ,  152 ,  153  in the base  150  are female screws threaded on the inner circumference. Thus, the distal ends of the fixing members  11 ,  12 ,  13 , which are screw members, can be screwed into the holes  151 ,  152 ,  153  in the base  150 . This enables the fixing of the sensor unit  20 , the substrate  40 , the protection plates  160 ,  170  and the like to the base  150 . The holes  21 ,  22 ,  23  in the sensor unit  20 , the holes  161 ,  162 ,  163  in the protection plate  160 , and the holes  171 ,  172 ,  173  in the protection plate  170  are not threaded on the inner circumference. However, a modified embodiment where these holes are threaded can be employed as well. 
     As shown in  FIG. 3 , spacers  14 ,  15 ,  16  are provided at positions corresponding to the holes  41 ,  42 ,  43  in the substrate  40 . Also, spacers  17 ,  18 ,  19  are provided at positions corresponding to the holes  161 ,  162 ,  163  in the protection plate  160 . When fixing, the fixing members  11 ,  12 ,  13  penetrate the holes in these spacers  14 ,  15 ,  16 ,  17 ,  18 ,  19 . Providing such spacers  14 ,  15 ,  16 ,  17 ,  18 ,  19  enables provision of a space between the substrate  40  and the protection plate  160  and between the protection plate  160  and the protection plate  170 . 
     Also, a modified embodiment where the holes in the spacers  14 ,  15 ,  16 ,  17 ,  18 ,  19  are formed as female screws threaded on the inner circumference can be employed as well. As shown in  FIG. 3 , the substrate  48  can be installed as supported by the substrate  40  using a support part  44 . The protection plate  160  is provided with a slit  164 . As the support part  44  is installed in such a way as to penetrate the slit  164 , the protection plate  160  is arranged between the substrate  40  and the substrate  48 . 
       FIG. 4  is a side view of the inertial measurement unit  10 .  FIG. 5  is a bottom view. As shown in  FIG. 4 , the sensor unit  20  is provided between the base  150  and the substrate  40 . The substrate  40  is provided between the sensor unit  20  and the protection plate  160 . The substrate is provided between the protection plate  160  and the protection plate  170 . As described with reference to  FIG. 3 , the fixing members  11 ,  12 ,  13 , which are columnar members, are provided in such a way as to fit into the holes provided in each of the base  150 , the sensor unit  20 , the substrate  40 , the protection plate  160 , the substrate  48 , and the protection plate  170 . Thus, these members can be removably fixed. 
     As shown in  FIGS. 4 and 5 , the base  150  has fixing parts  156 ,  157  at the bottom surface thereof facing the installation surface  2 . The fixing parts  156 ,  157  are magnets, that is, magnetic bodies. The fixing parts  156 ,  157  are attached to the bottom surface of the base  150 , for example, with a screw. Thus, the fixing parts  156 ,  157  can be removably attached to the base  150 . For example, the fixing parts  156 ,  157  are cubic. The bottom surfaces of the fixing parts  156 ,  157  come into contact with the installation surface  2 . As such fixing parts  156 ,  157 , which are magnets, are provided at the bottom surface of the base  150 , the inertial measurement unit  10  can be easily installed, for example, at a metal surface or the like of a device by the magnetic force of the magnets. 
       FIG. 6  is a plan view of the protection plate  160 . As shown in  FIG. 6 , the protection plate  160  is provided with the holes  161 ,  162 ,  163  to be penetrated by the fixing members  11 ,  12 ,  13 , which are columnar members. The protection plate  160  is also provided with the slit  164  to be penetrated by the support part  44  for supporting the substrate  48 . In  FIG. 6 , the protection plate  160  is shown as a transparent plate-like member. 
       FIG. 7  is a plan view of the protection plate  170 . As shown in  FIG. 7 , the protection plate  170  is provided with the holes  171 ,  172 ,  173  to be penetrated by the fixing members  11 ,  12 ,  13 . The screw heads of the fixing members  11 ,  12 ,  13 , which are screw members, are located above the holes  171 ,  172 ,  173 , as shown in  FIG. 3 . The protection plate  170  is also provided with the window  174  so that the user can view the display unit  70  below. The protection plate  170  is also provided with windows  175 ,  176  so that the user can view the light-emitting element groups  62 ,  64  of the display unit  60  below. In  FIG. 7 , the protection plate  170  is shown as a semitransparent plate-like member colored in a predetermined color such as blue. On the protection plate  170 , letters for explaining the functions of switches, described later, and letters for notifying the content of display information at the light-emitting element groups  62 ,  64 , are written. 
       FIG. 8  is a plan view of the display unit  70 . The display unit  70  has the display panel  72 . A signal line for transmitting a drive signal for the display panel  72  is electrically coupled to a coupling terminal in the display unit  70  from the substrate  40  below, via the support part  44  and the substrate  48 . This coupling terminal is provided, for example, on the right side of the display panel  72  as viewed in  FIG. 8 . 
     As described above, the inertial measurement unit  10  according to this embodiment includes: the sensor unit  20  having at least one inertial sensor; the substrate  40  provided with at least one of the processing unit  50  performing processing based on detection information from the inertial sensor and the display unit  60  performing a display based on the detection information; and at least one fixing member  11 ,  12 ,  13  removably fixing the sensor unit  20  and the substrate  40  together. 
     In the inertial measurement unit  10  according to this embodiment, the processing unit  50  provided at the substrate  40  can execute processing based on detection information from the inertial sensor of the sensor unit  20 , and the display unit  60  provided at the substrate  40  can perform a display based on the detection information. In  FIG. 1 , the display unit  60  having the light-emitting element groups  62 ,  64  is provided at the substrate  40 . However, the display unit  70  having the display panel  72  may be provided at the substrate  40 , as shown in  FIG. 2 . 
     In this embodiment, the sensor unit  20  and the substrate  40  are removably fixed together using the fixing members  11 ,  12 ,  13 , as shown in  FIG. 3 . For example, the sensor unit  20  and the substrate  40  are fixed together in a freely removable manner. Thus, the type of the sensor unit  20  and the type of the substrate  40  incorporated into the inertial measurement unit  10  can be freely changed. For example, the sensor unit  20  having an acceleration sensor can be incorporated into the inertial measurement unit  10 , or the sensor unit  20  having both of an acceleration sensor and an angular velocity sensor, or the like, can be incorporated into the inertial measurement unit  10 . Alternatively, the substrate  40  provided only with the processing unit  50  can be incorporated into the inertial measurement unit  10 , or the substrate  40  provided only with the display unit  60  can be incorporated into the inertial measurement unit  10 . Also, the substrate  40  provided with both of the processing unit  50  and the display unit  60 , or the like, can be incorporated into the inertial measurement unit  10 . Thus, various demands by the user using the inertial measurement unit  10  can be met and the extensibility of the inertial measurement unit  10  can be improved. Also, the inertial measurement unit  10  can be installed at the installation surface  2  in the state where the sensor unit  20  and the substrate  40  are firmly fixed together via the fixing members  11 ,  12 ,  13 . Therefore, a situation where an unwanted vibration or the like due to resonance or the like is transmitted to the inertial measurement unit  10  and adversely affects the measurement by the inertial measurement unit  10  can be restrained. Thus, the inertial measurement unit  10  in which extensibility can be improved while deterioration in the accuracy of measurement is restrained can be provided. 
     For example, according to the related art, the sensor unit  20  itself is used as the inertial measurement unit  10 , and the detection information from the inertial sensor of the sensor unit  20  is outputted from a connector  26  shown in  FIGS. 15 to 17 , described later. For example, acceleration information and angular velocity information detected by the inertial sensor are outputted directly as the detection information. However, handling the detection information from the inertial sensor is difficult and needs expertise, and therefore has the problem of poor user-friendliness. In this case, a technique such as coupling a PC (personal computer) to the connector  26  of the sensor unit  20 , then using the PC to perform various kinds of processing such as analysis processing on the detection information, and displaying the result of the analysis at the display unit, may be employed. However, in this technique, the PC needs to be coupled to the sensor unit  20  to perform various kinds of work. Therefore, the technique has a problem in that the work becomes complicated and that the scale of the measuring system increases. 
     In contrast, in this embodiment, the sensor unit  20  and the substrate  40  are fixed together via the fixing members  11 ,  12 ,  13 , thus forming the inertial measurement unit  10 . Therefore, processing such as analysis processing on detection information from the inertial sensor of the sensor unit  20  can be performed using the processing unit  50  provided at the substrate  40 , and a display based on the detection information can be performed using the display unit  60  provided at the substrate  40 . For example, there is no need to couple a PC to the inertial measurement unit  10  to perform processing based on detection information or to perform a display based on the detection information. Therefore, user-friendliness can be improved. That is, simply installing the inertial measurement unit  10  to a measuring target enables processing based on detection information or a display based on the detection information. For example, when the measuring target is a device such as a manufacturing device or measuring device, or a floor surface where the device is installed, the inertial measurement unit  10  is installed on the installation surface  2  that is a surface of the device or the floor surface. Then, the processing unit  50  executes processing to analyze a vibration of the device or the floor surface. Information about the result of the processing can be outputted to outside via the wireless communication unit  90  and the interface unit  100 , or the result of the analysis can be displayed at the display unit  60 . Thus, the state of the measuring target can be monitored by a highly portable, low-cost and small-scale system. 
     For example, for a user who needs only acceleration information, the inertial measurement unit  10  in which the sensor unit  20  provided with an acceleration sensor as an inertial sensor and the substrate  40  are fixed together via the fixing members  11 ,  12 ,  13  is provided. For a user who need both of acceleration information and angular velocity information, the inertial measurement unit  10  in which the sensor unit  20  provided with both of an acceleration sensor and an angular velocity sensor as an inertial sensor and the substrate  40  are fixed together via the fixing members  11 ,  12 ,  13  is provided. For a user who wants the display unit  70  having the display panel  72 , the inertial measurement unit  10  in which the sensor unit  20 , the substrate  40 , and the substrate  48  provided with the display unit  70  are fixed together via the fixing members  11 ,  12 ,  13 , as shown in  FIG. 2 , is provided. In this way, the inertial measurement unit  10  meeting various demands by the user can be provided and the extensibility of the inertial measurement unit  10  can be increased. Also, since the inertial measurement unit  10  in which the sensor unit  20  and the substrate  40  are firmly fixed together via the fixing members  11 ,  12 ,  13  can be provided, it is advantageous in that deterioration in the accuracy of the result of measurement by the inertial measurement unit  10  due to an unwanted vibration or the like such as resonance can be restrained. 
     In  FIGS. 1 and 2 , both of the processing unit  50  and the display unit  60  are provided at the substrate  40 . However, at least one of the processing unit  50  and the display unit  60  may be provided at the substrate  40 . For example, when the processing unit  50  is not provided at the substrate  40 , processing based on detection information may be performed, for example, using a processing unit  212 , described later, provided in the sensor unit  20 . Alternatively, the processing unit  50  may be provided at the substrate  48  located above the substrate  40 . The display unit  60  may be provided at the substrate  48  instead of at the substrate  40 . Alternatively, the display unit  60  using a light-emitting element may not be provided as a display unit in the inertial measurement unit  10 . The display unit  70  having the display panel  72  may be provided at the substrate  40 . 
     In this embodiment, as shown in  FIG. 3 , the inertial measurement unit  10  includes a plurality of columnar members as the fixing members  11 ,  12 ,  13 . As the fixing members  11 ,  12 ,  13 , which are the plurality columnar members, fit into the plurality of holes  41 ,  42 ,  43  provided in the substrate  40  and the plurality of holes  21 ,  22 ,  23  provided in the sensor unit  20 , the sensor unit  20  and the substrate  40  are removably fixed together. Thus, various combinations of sensor unit  20  and substrate  40  can be freely attached or removed from each other and removable fixing of the sensor unit  20  and the substrate  40  can be realized. For example, replacing the sensor unit  20  with a sensor unit of a different type and inserting the fixing members  11 ,  12 ,  13  into the holes  21 ,  22 ,  23  in the sensor unit can change the type of the sensor unit  20 . Also, replacing the substrate  40  with a substrate of a different type and inserting the fixing members  11 ,  12 ,  13  into the holes  41 ,  42 ,  43  in the substrate can change the type of the substrate  40 . Thus, sensor units  20  and substrates  40  of various types can be provided as option parts for the user, and the extensibility of the inertial measurement unit  10  can be significantly improved. 
     For example, the fixing members  11 ,  12 ,  13 , which are a plurality of columnar members, are screw members. For example, the fixing members  11 ,  12 ,  13  are male screws threaded on the outer circumference. Using screw members as the fixing members  11 ,  12 ,  13  in this way enables screw-fixing with the screw members. Therefore, the sensor unit  20 , the substrate  40  and the like can be fixed firmly and stably. Thus, deterioration in the accuracy of the result of measurement by the inertial measurement unit  10  due to an unwanted vibration or the like caused by resonance or the like can be restrained further. Also, the work of attaching the sensor unit  20 , the substrate  40  and the like becomes easier and work efficiency or the like is improved. 
     The inertial measurement unit  10  also includes the base  150  for installing the inertial measurement unit  10  at the installation surface  2 . The sensor unit  20  is provided between the base  150  and the substrate  40 . The base  150  is fixed to the sensor unit  20  via at least one fixing member  11 ,  12 ,  13 . For example, the base  150  is a member serving as a base stand for installing the inertial measurement unit  10  at the installation surface  2 . As the bottom surface or the like of the base  150  comes into contact with the installation surface  2 , the inertial measurement unit  10  is installed on the installation surface  2 . The installation surface  2  is, for example, a surface of a device such as a manufacturing device or measuring device, or a floor surface or the like where the device is installed. The installation surface  2  is a surface of a measuring target. The sensor unit  20  is fixed by the fixing members  11 ,  12 ,  13  in such a way as to be held between the substrate  40  and the base  150 . Such fixing can restrain deterioration in the accuracy of detection of the inertial sensor of the sensor unit  20  due to a vibration or the like caused by resonance or the like. Even when the bottom surface of the sensor unit  20  does not have a suitable shape for installation on the installation surface  2 , the bottom surface of the base  150  instead of the bottom surface of the sensor unit  20  can be attached to the installation surface  2 , and this enables table installation of the inertial measurement unit  10 . For example, stable installation can be achieved regardless of the shape and type of the sensor unit  20 , and detection errors or the like due to wobbly installation can be prevented. 
     As shown in  FIGS. 4 and 5 , the base  150  has the fixing parts  156 ,  157 , which are magnets, on the surface facing the installation surface  2 . That is, the fixing parts  156 ,  157  for fixing the inertial measurement unit  10  to the installation surface  2  are provided at the bottom surface of the base  150 . These fixing parts  156 ,  157  are magnets. For example, the fixing parts  156 ,  157  are cubic magnets. Thus, the bottom surfaces of the fixing parts  156 ,  157  are attracted to a metal surface or the like of a device, as the installation surface  2 , by the magnetic force of the magnets. Therefore, simply bringing the bottom surfaces of the fixing parts  156 ,  157  into contact with the installation surface  2  enables the inertial measurement unit  10  to be fixed and installed at the installation surface  2  by the magnets. This makes it easier for the user to carry out installation work and can improve work efficiency. 
     Although  FIGS. 4 and 5  show an example where the number of the fixing parts  156 ,  157  is two, the number of fixing parts is not limited to this and may be, for example, three or more. The base  150  itself or a part of the base  150  may be a magnet. 
     As shown in  FIGS. 4 and 5 , the base  150  has the recess  154  on the surface facing the installation surface  2 . That is, the bottom surface, which is the surface facing the installation surface  2 , of the base  150  has the recess  154  recessed in the direction DR 4 , which is the opposite direction of the direction DR 1 . In cases such as where the inertial measurement unit  10  is installed at the installation surface  2  via a double-sided adhesive tape, the provision of such a recess  154  can make it easier to strip off the double-sided adhesive tape. That is, in this embodiment, the inertial measurement unit  10  can be installed at the installation surface  2 , using a double-sided adhesive tape instead of using the fixing parts  156 ,  157 . Specifically, one side of the double-sided adhesive tape is attached to the bottom surface of the base  150 , and the other side of the double-sided adhesive tape is attached to the installation surface  2 . Thus, the inertial measurement unit  10  can be installed at the installation surface  2  by simple work and can be installed at the installation surface  2  even when, for example, the installation surface  2  is not a metal surface. In this case, after measurement is finished and the inertial measurement unit  10  is removed from the installation surface  2 , the double-sided adhesive tape needs to be stripped off from the bottom surface of the base  150 . In this regard, the provision of the recess  154  at the bottom surface of the base  150  enables the user as a worker to insert a finger or the like into this recess  154  and thus easily strip off the double-sided adhesive tape from the bottom surface of the base  150 . The inertial measurement unit  10  can also be installed via a screw as well as the magnets and the double-sided adhesive tape. 
     As shown in  FIGS. 1 and 2 , the substrate  40  is provided with the wireless communication unit  90  wirelessly transmitting information based on detection information from the inertial sensor. For example, a wireless communication IC that is the wireless communication unit  90  is provided at the substrate  40 . The wireless communication unit  90  transmits the information based on the detection information from the inertial sensor, to outside. For example, when the processing unit  50  performs processing such as analysis processing based on the detection information from the inertial sensor, the wireless communication unit  90  transmits information about the result of the processing, to outside. Alternatively, the wireless communication unit  90  may transmit the detection information itself from the inertial sensor, to outside. Thus, the information based on the detection information from the inertial sensor can be wirelessly transmitted to an external device, even without coupling the inertial measurement unit  10  and the external device together via a wire. For example, the information based on the detection information detected by the inertial sensor can be transmitted to the external device, using the wireless communication unit  90 , in the state where the inertial measurement unit  10  remains installed at the installation surface  2 . Therefore, improved convenience or the like can be achieved. 
     The substrate  40  is also provided with the interface unit  100  for wired communication with outside. For example, the interface unit  100  communicates with outside by such a communication interface format as UART, GPIO or SPI. For example, the interface unit  100  transmits information based on detection information from the inertial sensor, to an external device. The provision of such an interface unit  100  can meet various demands by the user with respect to the communication interface. For example, UART can be converted to RS-232C so as to couple the inertial measurement unit  10  to various devices. Also, UART can be converted to Ethernet (trademark registered). Moreover, the inertial measurement unit  10  can be coupled to an SD (trademark registered) card slot device, using SPI. Thus, user-friendliness can be improved. 
     The substrate  40  is also provided with at least one of the mode changeover switch  80  for changing the mode of the inertial measurement unit  10 , the reset switch  82  for resetting the inertial measurement unit  10 , and the measurement start switch  84  for starting measurement by the inertial measurement unit  10 . In  FIGS. 1 and 2 , all of these switches are provided. However, in this embodiment, at least one of these switches may be provided. As such various switches are provided, the user can operate each of these switches to cause the inertial measurement unit  10  to carry out various operations. This can make the measuring work simpler and more efficient. When the user operates the mode changeover switch  80 , the inertial measurement unit  10  switches between various modes. Specifically, the display mode in the display units  60 ,  70  is changed. When the user operates the reset switch  82 , the inertial measurement unit  10  becomes reset. When the user operates the measurement start switch  84 , the inertial measurement unit  10  starts measurement. The measurement start switch  84  also functions as a measurement end switch. For example, when the user presses the measurement start switch  84  before starting measurement, the inertial measurement unit  10  shifts into a state monitoring mode and starts measurement. Then, when the user presses measurement start switch  84  again, the state monitoring mode ends. The measurement start switch  84  also functions as a teach switch, as described later. 
     The inertial measurement unit  10  also includes the protection plate  160 . The substrate  40  is provided between the sensor unit  20  and the protection plate  160 . For example, the protection plate  160  is arranged above the substrate  40 , that is, in the direction DR 4  from the substrate  40 , via a gap space formed by the spacers  14 ,  15 ,  16 . Thus, a dustproof function by the protection plate  160  can be realized. Also, the protection plate  160 , as a protection member, can prevent an unwanted impact from being applied to the components arranged at the substrate  40 , such as the processing unit  50 , the display unit  60 , and the wireless communication unit  90 . Also, for example, in  FIG. 1 , the user can hold the inertial measurement unit  10  in a hand with its palm in contact with the top surface of the protection plate  160  and thus install the inertial measurement unit  10  at the installation surface  2 . The provision of the protection plate  160  makes it easier for the user to manually hold the inertial measurement unit  10  and thus makes the installation work easier and more efficient. 
     The inertial measurement unit  10  includes, as a substrate, the substrate  40  as the first substrate, and the substrate  48  as the second substrate, as shown in  FIG. 2 . The substrate  40  as the first substrate is provided with the processing unit  50 . The substrate  48  as the second substrate is provided with the display unit  70  having the display panel  72 . Thus, for example, processing based on detection information from the inertial sensor of the sensor unit  20  is executed by the processing unit  50  provided at the substrate  40 , and information about the result of the processing can be displayed on the display panel  72  of the display unit  70  provided at the substrate  48 . That is, the information based on the detection information can be displayed on the display panel  72 . The display panel  72  is formed of an organic EL panel or liquid crystal panel and therefore can perform a more detailed and advanced display of information than when a light-emitting element is used. For example, numbers and letters about a measured value can be displayed and more precise and advanced changeover processing about the display mode can be implemented. Thus, user-friendliness can be improved. Also, a modified embodiment where the display unit  70  having the display panel  72  is provided at the substrate  40  can be employed. 
     The inertial measurement unit  10  also includes the protection plate  160  as the first protection plate, and the protection plate  170  as the second protection plate. The substrate  40  is provided between the sensor unit  20  and the protection plate  160 . The substrate  48  is provided between the protection plate  160  and the protection plate  170 . For example, as shown in  FIG. 3 , the protection plate  170  is arranged above the protection plate  160 , that is, in the direction DR 4  from the protection plate  160 , via a gap space formed by the spacers  17 ,  18 ,  19  provided at the holes  161 ,  162 ,  163  in the protection plate  160 . The substrate  48  is arranged in this gap space. Thus, the protection plate  160  can protect the components provided at the substrate  40 . For example, the components provided at the substrate  40 , such as the processing unit  50 , the wireless communication unit  90 , and the display unit  60 , can be protected. The protection plate  170  can protect the components provided at the substrate  48 . For example, the components provided at the substrate  48 , such as the display unit  70 , can be protected. Thus, damage or the like to the components of the inertial measurement unit  10 , for example, due to a touch by the user, can be effectively prevented. 
     The substrate  40  is also provided with the display unit  60  having the light-emitting element groups  62 ,  64 . That is, the display unit  60  formed of the light-emitting element groups  62 ,  64  such as LEDs is provided. Thus, the display of information based on detection information from the inertial sensor of the sensor unit  20  can be implemented via an indication operation based on light emission of the light-emitting elements of the light-emitting element groups  62 ,  64 . For example, information about whether the result of measurement satisfies a determination criterion or not, or the like, can be sufficiently communicated via light emission of the light-emitting elements. The light-emitting elements are available at a lower cost than the display panel  72  and therefore can achieve cost reduction or the like of the inertial measurement unit  10 . 
     2. Switches 
     In this embodiment, the user holds the inertial measurement unit  10  in such a way that the bottom surface of the inertial measurement unit  10  comes into contact with the installation surface  2 , then installs the inertial measurement unit  10 , using a double-sided adhesive tape, magnet, screw or the like, and carries out measurement with the inertial measurement unit  10 . In this case, it is desired that, when measuring with the inertial measurement unit  10 , the user can easily carry out operations such as mode setting and measurement start instruction for the inertial measurement unit  10 . Thus, in this embodiment, the inertial measurement unit  10  is provided with various switches such as the mode changeover switch  80 , the reset switch  82 , and the measurement start switch  84 , as shown in  FIG. 9 . The mode changeover switch  80  is a switch for changing the mode of the inertial measurement unit  10  and specifically a switch for changing the display mode of the display unit  70 . For example, the mode changeover switch  80  is a switch for changing the mode of display information. The reset switch  82  is a switch for resetting the inertial measurement unit  10 . Pressing the reset switch  82  initializes the inertial measurement unit  10 . The measurement start switch  84  is a switch for starting measurement by the inertial measurement unit  10 . The measurement start switch  84  also functions as a switch for ending measurement by the inertial measurement unit  10 . When long-pressed, the measurement start switch  84  functions as a teach switch for giving an instruction to store measurement criteria information for inertial measurement into a memory. Also, the mode changeover switch  80 , when long-pressed, functions as a switch for saving measurement log data. A slide switch  86  is a switch for selecting wireless communication and a communication interface. 
     The display unit  70  performs a display based on detection information from the inertial sensor of the sensor unit  20 . For example, in  FIG. 9 , the display unit  70  shows that a measured vibration satisfies VC-B of VC (vibration criteria), which are ambient vibration criteria. The display unit  70  also shows information about vibration displacement. In this embodiment, the display mode of the display unit  70  changes via the mode changeover switch  80 . For example, in  FIG. 10 , the display unit  70  shows a result of determination based on the VC standard. For example, the display unit  70  shows the result of determination that a measured vibration satisfies VC-B. That is, in a first display mode in  FIG. 10 , the result of determination based on a first determination criterion is displayed. Meanwhile, in  FIG. 11 , the display unit  70  shows a result of measurement based on a determination criterion set by the user. For example, the display unit  70  shows the result of determination that what percentage of a threshold set by the user is reached. That is, in a second display mode in  FIG. 11 , the result of determination based on a second determination criterion is displayed. For example, pressing the mode changeover switch  80  results in the first display mode in  FIG. 10  or the second display mode in  FIG. 11 . 
     Also, the unit of information displayed based on detection information from the inertial sensor changes via the mode changeover switch  80 . That is, the display mode changes in terms of unit via the mode changeover switch  80 . For example, in  FIG. 10 , the unit of vibration displacement, μm, is shown. Specifically, a peak frequency of vibration displacement and the vibration displacement at the peak frequency are shown. Pressing the mode changeover switch  80  changes the display of the unit to a display of the unit of vibration velocity, mm/s, or a display of the unit of vibration acceleration, Gal. Specifically, pressing the mode changeover switch  80  results in a display of a peak frequency of vibration velocity and the vibration velocity at the peak frequency, or a display of a peak frequency of vibration acceleration and the vibration acceleration at the peak frequency. For example, the result of determination based on VC is displayed at the beginning, and every time the mode changeover switch  80  is pressed, the display mode sequentially changes to the display of vibration acceleration and peak frequency thereof, the display of vibration velocity and peak frequency thereof, the display of vibration displacement and peak frequency thereof, and the display of the measured value in percentage terms to the threshold set by the user. 
     VC, which are ambient vibration criteria, define VC-A, VC-B, VC-C, VC-D, VC-E and the like. Showing which of these is satisfied enables the user to easily grasp the vibration level of an ambient vibration or the like. The threshold set by the user is stored, for example, into the memory  102  in  FIG. 1 , which is a non-volatile memory, for example, based on the setup by the user. Alternatively, a threshold may be set via the teach switch, described later. 
     As shown in  FIG. 9 , the mode changeover switch  80  has a moving part  81 . The moving part  81  is implemented, for example, by a push-button. It is now assumed that the direction from the inertial measurement unit  10  toward the installation surface  2  is defined as DR 1  and that a direction orthogonal to the direction DR 1  is defined as DR 2 . The direction DR 1  is a first direction. The direction DR 2  is a second direction. The direction DR 2  is, for example, a direction along the main surface, that is, the top surface of the sensor unit  20  and the main surface, that is, the top surface of the substrate  40 , and for example, along the shorter sides of the sensor unit  20  and the substrate  40 . In this case, the moving part  81  is movable in the direction DR 2 . That is, the push-button as the moving part  81  is movable and can be pressed along a directions indicated by A 1  in  FIG. 9 . The movement of the moving part  81  of the mode changeover switch  80  gives an instruction to change the display mode of the display unit  70 . That is, pressing the push-button as the moving part  81  results in the change in the display mode described with reference to  FIGS. 10 and 11 . 
     The moving part  81  of the mode changeover switch  80 , when not pressed, protrudes from a side of the sensor unit  20  as viewed in a plan view in the direction DR 1 . For example, in  FIG. 9 , a side SD 1  is a first shorter side of the substrate  40 , and a side SD 2  is a second shorter side opposite the side SD 1 . A side SD 3  is a first longer side of the substrate  40 , and a side SD 4  is a second longer side opposite the side SD 3 . The mode changeover switch  80  is arranged on the side SD 3 , which is a longer side of the substrate  40 . The reset switch  82  and the measurement start switch  84 , too, are arranged on the side SD 3 . That is, the mode changeover switch  80 , the reset switch  82 , and the measurement start switch  84  are arrayed along the side SD 3 . The moving part  81  of the mode changeover switch  80 , when not pressed, protrudes from the side SD 3  of the substrate  40  and also protrudes from the side of the sensor unit  20  corresponding to the side SD 3  of the substrate  40 , as viewed in a plan view. That is, when not pressed, the push-button as the moving part  81  protrudes from the side SD 3 . Thus, for example, when the user holds the inertial measurement unit  10  with the palm in contact with the top surface thereof, the user can press the moving part  81 , for example, using a finger of the hand. Therefore, while holding the inertial measurement unit  10 , the user can press the push-button as the moving part  81  of the mode changeover switch  80  with a finger of the hand and thus can easily change the display mode of the display unit  70 . For example, the user can attach the bottom surface of the inertial measurement unit  10  to the installation surface  2  and operate the mode changeover switch  80  with a hand&#39;s finger. Therefore, user-friendliness can be improved. 
     The reset switch  82  similarly has a moving part  83 . The moving part  83  can be pressed along directions indicated by A 2  in  FIG. 9 . However, the moving part  83 , when not pressed, does not protrude from the side SD 3  of the substrate  40  and does not protrude from the side of the sensor unit  20  and the side of the protection plate  160  corresponding to the side SD 3 , either. That is, since pressing the moving part  83  of the reset switch  82  initializes the inertial measurement unit  10 , the moving part  83  does not protrude from the side SD 3 . Thus, the user can be prevented from making an erroneous operation such as making a reset operation by mistake. 
     The measurement start switch  84  similarly has a moving part  85  movable in the direction DR 2 . The movement of the moving part  85  of the measurement start switch  84  gives an instruction to start measurement by the inertial measurement unit  10 . That is, a push-button that is the moving part  85  can be moved and pressed along directions indicated by A 3  in  FIG. 9 . Pressing the push-button as the moving part  85  starts measurement by the inertial measurement unit  10 . Then, pressing the push-button as the moving part  85  again after the measurement is started ends the measurement. That is, the measurement start switch  84  also functions as a measurement end switch. 
     The moving part  85  of the measurement start switch  84 , when not pressed, protrudes from the side SD 3  of the substrate  40  and protrudes from the side of the sensor unit  20  corresponding to the side SD 3 , as viewed in a plan view. That is, when not pressed, the push-button as the moving part  85  protrudes from the side SD 3 . Thus, for example, when the user holds the inertial measurement unit  10  with the palm in contact with the top surface thereof, the user can press the moving part  85 , for example, using a finger of the hand. Therefore, while holding the inertial measurement unit  10 , the user can press the push-button as the moving part  85  of the measurement start switch  84  with a finger of the hand and thus can easily start measurement. Therefore, user-friendliness can be improved. 
     In this embodiment, the measurement start switch  84  also functions as a teach switch, which is a switch for giving an instruction to store measurement criteria information for inertial measurement into the memory  102 . That is, the measurement start switch  84  functions as a teach switch for causing the inertial measurement unit  10  to learn measurement criteria information. Specifically, for example, a long press on the measurement start switch  84  by the user causes the measurement start switch  84  to functions as a teach switch. When the measurement start switch  84  functions as a teach switch, the teach switch has the moving part  85  movable in the direction DR 2  and the movement of the moving part  85  of the teach switch gives an instruction to store measurement criteria information into the memory  102 . Specifically, a long press on the measurement start switch  84  causes the inertial measurement unit  10  to shift to a learning mode, which is a teach mode. Then, the inertial measurement unit  10  performs measurement for learning during a predetermined learning period. Based on an average value or the like of measured values measured during the learning period, a threshold that serves as measurement criteria information is found. The threshold is stored as measurement criteria information into the memory  102 , which is a non-volatile memory. In actual measurement by the inertial measurement unit  10 , determination processing is performed using the threshold as the measurement criteria information, and the result of the determination is displayed at the display unit  70 . For example, the display as shown in  FIG. 11  is performed. 
     As described above, the inertial measurement unit  10  according to this embodiment includes the sensor unit  20  having at least one inertial sensor, the display unit  70  performing a display based on detection information from the inertial sensor, and the mode changeover switch  80 . The display mode of the display unit  70  changes via the mode changeover switch  80 . For example, the changeover of the display mode as described with reference to  FIGS. 10 and 11  is carried out. For example, the mode of display information at the display unit  70  is changed. 
     In the inertial measurement unit  10  of such a configuration, the display unit  70  provided in the inertial measurement unit  10  can perform a display based on detection information from the inertial sensor of the sensor unit. For example, simply installing the inertial measurement unit  10  on a measurement target enables the display unit  70  to display information based on detection information. Therefore, there is no need to couple the inertial measurement unit  10  to a PC and cause the display unit of the PC to perform a display based on detection information. Thus, the work of checking the result of measurement can be simplified and user-friendliness can be improved. When the user operates the mode changeover switch  80  provided in the inertial measurement unit  10 , the display mode of the display unit  70  changes. Specifically, as described with reference to  FIGS. 10 and 11 , when the user operates the mode changeover switch  80 , a change of the display mode takes place, such as displaying the result of determination about measurement at the display unit  70 , based on a different determination criterion, or changing the unit of information displayed at the display unit  70 . The simple operation of operating the mode changeover switch  80  can change the display mode of the display unit  70  in various forms. Thus, various demands about the display form of the result of measurement can be met and user-friendliness can be improved further. 
     In the inertial measurement unit  10  having the configuration described with reference to  FIG. 9 , the mode changeover switch  80  need not necessarily be provided at the substrate  40  and may be provided, for example, at other substrates than the substrate  40 . For example, the mode changeover switch  80  may be provided at the substrate  48 , where the display unit  70  is provided, instead of the substrate  40 , where the processing unit  50  or the like is provided. Alternatively, various modified embodiments, for example, installing the mode changeover switch  80  at the top surface of the sensor unit  20 , can be employed. 
     As shown in  FIG. 9 , the mode changeover switch  80  has the moving part  81  movable in the direction DR 2 , which is orthogonal to the direction DR 1  from the inertial measurement unit  10  toward the installation surface  2 . The movement of the moving part  81  of the mode changeover switch  80  gives an instruction to change the display mode of the display unit  70 . Thus, for example, the user can hold the inertial measurement unit  10  with the palm in contact with the top surface thereof and can move the moving part  81  in the direction DR 2  parallel to the top surface of the inertial measurement unit  10 , thus giving an instruction to change the display mode of the display unit  70 . Therefore, the user can give an instruction to change the display mode by a simple operation and can cause the display unit  70  to display information based on detection information from the inertial sensor, in a display mode desired by the user. 
     The moving part  81  of the mode changeover switch  80 , when not pressed, protrudes from a side of the sensor unit  20  as viewed in a plan view along the direction DR 1 . Thus, for example, when the user holds the inertial measurement unit  10  with the palm in contact with the top surface thereof, the moving part  81  of the mode changeover switch  80  is in a protruding state when not pressed. Therefore, while holding the inertial measurement unit  10 , the user can press the protruding moving part  81 , for example, with a finger of the hand, thus causing the display mode of the display unit  70  to change. The simple operation of pressing the moving part  81  protruding in a direction parallel to the top surface of the sensor unit  20  when not pressed, changes the display mode of the display unit  70 . Thus, user-friendliness can be improved. 
     The inertial measurement unit  10  also includes the measurement start switch  84  for starting measurement by the inertial measurement unit  10 . As such a measurement start switch  84  is provided, processing of giving a command to start measurement via a PC or the like is not needed. When wishing to start measurement, the user can start measurement by the inertial measurement unit  10  by the simple operation of pressing the measurement start switch  84 . 
     The measurement start switch  84  has the moving part  85  movable in the direction DR 2 , which is orthogonal to the direction DR 1  toward the installation surface  2 . The movement of the moving part  85  of the measurement start switch  84  gives an instruction to start measurement by the inertial measurement unit  10 . Thus, for example, the user can hold the inertial measurement unit  10  with the palm in contact with the top surface thereof and can move the moving part  85  in the direction DR 2  parallel to the top surface, thus giving an instruction to start measurement by the inertial measurement unit  10 . Therefore, the user can give an instruction to start measurement by the inertial measurement unit  10  by a simple operation at a timing desired by the user. 
     The inertial measurement unit  10  also includes the memory  102  and the teach switch for giving an instruction to store measurement criteria information for inertial measurement into the memory  102 . In  FIG. 9 , for example, the measurement start switch  84  is also used as the teach switch. When the measurement start switch  84  is long-pressed, the leaning mode sets in and a threshold as the measurement criteria information for inertial measurement is stored into the memory  102 . Then, for example, the processing unit  50  performs determination processing about measurement based on the threshold as the determination criterion, or the display unit  70  displays the result of the determination about measurement based on the threshold as the determination criterion. Thus, the inertial measurement unit  10  can be made to learn measurement criteria information corresponding to the state of a device as a measuring target or the ambient state, and can perform measurement using the measurement criteria information. 
     The teach switch, also used as the measurement start switch  84 , has the moving part  85  movable in the direction DR 2 . The movement of the moving part  85  of the teach switch gives an instruction to store measurement criteria information into the memory  102 . Thus, for example, the user can hold the inertial measurement unit  10  with the palm in contact with the top surface thereof and can move the moving part  85  in the direction DR 2  parallel to the top surface, thus giving an instruction to store measurement criteria information into the memory  102 . Therefore, the user can cause the inertial measurement unit  10  to learn measurement criteria information during a period when the user wants the inertial measurement unit  10  to learn the measurement criteria information. 
     The inertial measurement unit  10  also includes the substrate  40  provided with the mode changeover switch  80 . For example, the mode changeover switch  80  is provided at the substrate  40  where the processing unit  50  or the display unit  60  or the like is provided. For example, the mode changeover switch  80  is mounted at the substrate  40  arranged parallel to the top surface of the sensor unit  20 . Thus, the mode changeover switch  80  can be mounted in a compact form in the inertial measurement unit  10 . Particularly, making the direction of movement of the moving part  81  of the mode changeover switch  80  parallel to the surface of the substrate  40  enables the mode changeover switch  80  to be mounted compactly. 
     As described with reference to  FIGS. 1 and 2  or the like, the inertial measurement unit  10  includes at least one fixing member  11 ,  12 ,  13  for removably fixing the sensor unit  20  and the substrate  40  together. That is, the sensor unit  20  having the inertial sensor, and the substrate  40  provided with the mode changeover switch  80 , are removably fixed together via the fixing members  11 ,  12 ,  13 . Thus, the type of the sensor unit  20  and the type of the substrate  40  incorporated in the inertial measurement unit  10  can be freely changed, and the extensibility of the inertial measurement unit  10  can be improved. The inertial measurement unit  10  can be installed at the installation surface  2  in the state where the sensor unit  20  and the substrate  40  are fixed together via the fixing members  11 ,  12 ,  13 . Therefore, a situation where an unwanted vibration or the like due to resonance or the like is transmitted to the inertial measurement unit  10  and adversely affects the measurement can be restrained. 
     Also, the inertial measurement unit  10  includes the substrate  40  as the first substrate, and the substrate  48  as the second substrate. The mode changeover switch  80  is provided at the substrate  40 . The display unit  70  is provided at the substrate  48 . The substrate  40  is provided between the sensor unit  20  and the substrate  48 . Thus, when the mode changeover switch  80  provided at the substrate  40  is operated, the display mode of the display unit  70  provided at the substrate  48  changes. The mode changeover switch  80  is provided at the substrate  40  provided between the sensor unit  20  and the substrate  48  and therefore is arranged, for example, near the center in the direction of the height of the inertial measurement unit  10 . Therefore, the operability of the mode changeover switch  80  can be improved. Meanwhile, the display unit  70  is provided at the substrate  48  arranged above the substrate  40 , that is, in the direction DR 4  from the substrate  40 , and therefore can be arranged at a position visible to the user. 
     In the first display mode, the display unit  70  displays the result of determination based on the first determination criterion, as the result of determination in determination processing based on detection information. In the second display mode, the display unit  70  displays the result of determination based on the second determination criterion. For example, in the first display mode, the display unit  70  displays the result of determination as shown in  FIG. 10 , and in the second display mode, the display unit  70  displays the result of determination as shown in  FIG. 11 . Thus, the display mode can be switched between the first display mode, in which the result of determination based on the first determination criterion is displayed, and the second display mode, in which the result of determination based on the second determination criterion is displayed, via the mode changeover switch  80 . Therefore, as the user operates the mode changeover switch  80 , the result of determination about measurement is displayed at the display unit  70 , based on different determination criteria. This enables presentation of the result of determination based on various determination criteria to the user. 
     In this case, the first determination criterion is a determination criterion of VC (vibration criteria) and the second determination criterion is a determination criterion set by the user. For example, in the first display mode, the result of determination is displayed based on the determination criterion of VC as the first determination criterion, as shown in  FIG. 10 . For example, which of VC-A, VC-B, VC-C, VC-D, VC-E and the like as indicators of ambient vibration criteria is satisfied by a vibration measured by the inertial measurement unit  10  is displayed. Meanwhile, in the second display mode, the result of determination is displayed based on the determination criterion set by the user, as shown in  FIG. 11 . For example, what degree of the determination criterion set by the user is reached by the result of measurement by the inertial measurement unit  10  is displayed. For example, when the determination criterion set by the user is a threshold, what proportion of the threshold is reached by the measured value is displayed. Thus, the display mode can be switched between the first display mode, in which the result of determination based on the VC determination criterion is displayed, and the second display mode, in which the result of determination based on the determination criterion set by the user is displayed, via the mode changeover switch  80 . When the display unit  60  formed of the light-emitting element groups  62 ,  64  is used, which of VC-A, VC-B, VC-C, VC-D, VC-E and the like is satisfied is displayed using the light-emitting element group  62 , as clear from  FIG. 7 . Also, for example, which of L (low), M (middle), and H (high) the peak value is, is displayed using the light-emitting element group  64 . That is, one of the light-emitting elements corresponding to the positions of L, M, H emits light, thus displaying which of the low level, the middle level, and the high level the peak value is. “A” in  FIG. 7  represents an alarm state. When the light-emitting element corresponding to the position of “A” emits light, the user is notified that the alarm state has set in, such as where the measured value exceeds the threshold. 
     The mode changeover switch  80  also changes the unit of information displayed based on detection information. For example, in the case of measuring a vibration, the unit of the displayed measured value changes to the unit of vibration displacement (μm), the unit of vibration velocity (mm/s), and the unit of vibration acceleration (Gal) or the like, in response to an operation on the mode changeover switch  80 , as shown in  FIG. 10 . Thus, in response to the operation on the mode changeover switch  80 , the measured value can be displayed in various units to the user. Therefore, user-friendliness can be improved. 
     The inertial measurement unit  10  includes the processing unit  50  performing processing based on detection information. The processing unit  50  performs analysis processing on vibration information of a detection target. The display unit  70  displays information about the result of the analysis processing. The display unit  60  similarly displays information about the result of the analysis processing. For example, the processing unit  50  performs analysis processing such as FFT analysis on vibration information, based on detection information from the inertial sensor of the sensor unit  20 . The display unit  70  displays, for example, a peak frequency of vibration, vibration displacement at the peak frequency, vibration velocity, or vibration acceleration or the like, as the information about the result of the analysis processing. Thus, even when detection information from the inertial sensor is difficult for the user to handle, the processing unit  50  performs analysis processing on this detection information and the display unit  70  displays information about the result of the analysis processing, enabling the user to easily grasp the vibration state of the detection target. 
     3. Wireless Communication Unit, Antenna Unit 
     The inertial measurement unit  10  according to this embodiment is provided with the wireless communication unit  90  for wirelessly transmitting, to outside, information based on detection information from the inertial sensor of the sensor unit  20 , and the antenna unit  92  coupled to the wireless communication unit  90 . The wireless communication unit  90  is, for example, a device performing near-field wireless communication such as Bluetooth (trademark registered, hereinafter simply referred to as BT) and is implemented by a wireless communication IC, which is an integrated circuit device, or the like. The wireless communication performed by the wireless communication unit  90  is not limited to BT and may be near-field wireless communication of another type such as ZigBee or Wi-SUN or may be Wi-Fi (trademark registered) wireless communication. Meanwhile, as described with reference to  FIGS. 15 to 17  later, the sensor unit  20  includes the sensor substrate  210  provided with the inertial sensor, and the electrically conductive case  24  accommodating the sensor substrate  210 . The case  24  includes, for example, a container  220  and a lid  222 . The sensor substrate  210  is accommodated in an accommodation space formed by the container  220  and the lid  222 . In  FIG. 15 , acceleration sensors  30 X,  30 Y,  30 Z are provided as the inertial sensor at the sensor substrate  210 . The acceleration sensors  30 X,  30 Y,  30 Z detect information about an acceleration in directions along an X-axis, a Y-axis, and a Z-axis, respectively, as detection information. In  FIGS. 16 and 17 , an acceleration sensor  32  and angular velocity sensors  34 X,  34 Y,  34 Z are provided as the inertial sensor at the sensor substrate  210 . The acceleration sensor  32  detects information about an acceleration in directions along the X-axis, the Y-axis, and the Z-axis, as detection information. The angular velocity sensors  34 X,  34 Y,  34 Z detect information about an angular velocity about the X-axis, the Y-axis, and the Z-axis, respectively, as detection information. 
     In  FIGS. 15 to 17 , the case  24  is formed of an electrically conductive material such as a metal. Since the sensor substrate  210  where the inertial sensor is installed is thus accommodated in the electrically conductive case  24 , adverse effects of external electromagnetic waves or the like on the inertial sensor can be reduced. For example, when the electrically conductive case  24  is not provided, external electromagnetic waves or the like may cause the problem of drift in the detection information from the inertial sensor. However, providing the inertial sensor in the electrically conductive case  24  can restrain the occurrence of such a problem. 
     Meanwhile, it has been found that the sensitivity of the antenna unit  92  drops when such an electrically conductive case  24  is located near the antenna unit  92 . For example, the antenna unit  92  is implemented by an inductor of a metal wiring formed at the substrate. For example, when the inductor of the metal wiring of the antenna unit  92  is located directly above the electrically conductive case  24 , the sensitivity of the antenna unit  92  drops significantly. 
     Thus, in this embodiment, as shown in  FIG. 12 , when the direction from the inertial measurement unit  10  toward the installation surface  2  is defined as DR 1 , the antenna unit  92  is provided in such a way as to protrude from a side of the case  24  of the sensor unit  20 , as viewed in a plan view in the direction DR 1 . For example, in  FIG. 12 , the substrate  40  has sides SD 1 , SD 2  as shorter sides opposite each other, and sides SD 3 , SD 4  as longer sides opposite each other. The direction from the side SD 1  toward the side SD 2  is DR 3 . The opposite direction of DR 3  is DR 6 . The direction from the side SD 3  toward the side SD 4  is DR 2 . The opposite direction of DR 2  is DR 5 . The antenna unit  92  protrudes from the side SD 1 , which is a shorter side of the substrate  40 . The antenna unit  92  also protrudes from the side of the sensor unit  20  corresponding to the side SD 1 . Specifically, the antenna unit  92  is provided in such a way as to protrude in the direction DR 6  from the side SD 1 . 
     Thus, for example, the antenna unit  92  is not located directly above the electrically conductive case  24  of the sensor unit  20 . Specifically, the inductor of the metal wiring of the antenna unit  92  is not located directly above the electrically conductive case  24 . Therefore, the drop in the sensitivity of the antenna unit  92  due to the electrically conductive case  24  can be restrained. That is, when the antenna unit  92  is provided in the direction DR 3  from the side SD 1  in  FIG. 12 , the presence of the electrically conductive case  24  causes a drop in the sensitivity of the antenna unit  92 . However, when the antenna unit  92  is provided in the direction DR 6  from the side SD 1  as shown in  FIG. 12 , the electrically conducive case  24  is not present directly below the antenna unit  92  and the sensitivity of the antenna unit  92  can be improved accordingly. 
     As described above, the inertial measurement unit  10  according to this embodiment includes the sensor unit  20  having at least one inertial sensor, the wireless communication unit  90  wirelessly transmitting information based on detection information from the inertial sensor, and the antenna unit  92  coupled to the wireless communication unit  90 . Providing the wireless communication unit  90  and the antenna unit  92  in this way enables wireless transmission of information based on detection information from the inertial sensor, to outside. Thus, the information based on the detection information can be transmitted to an external device, for example, even without coupling the inertial measurement unit  10  to the external device. Therefore, user-friendliness can be improved. 
     The sensor unit  20  includes the inertial sensor, the sensor substrate  210  provided with the inertial sensor, and the electrically conductive case  24  accommodating the sensor substrate  210 . That is, in  FIG. 15 , the sensor substrate  210  provided with the acceleration sensors  30 X,  30 Y,  30 Z as the inertial sensor is accommodated in the case  24 . In  FIGS. 16 and 17 , the sensor substrate  210  provided with the acceleration sensor  32  and the angular velocity sensors  34 X,  34 Y,  34 Z as the inertial sensor is accommodated in the case  24 . Thus, the inertial sensor is accommodated in the electrically conductive case  24  and therefore deterioration in the accuracy of detection information from the inertial sensor due to external electromagnetic waves or the like can be restrained. 
     As shown in  FIG. 12 , in the inertial measurement unit  10  according to this embodiment, the antenna unit  92  is provided in such a way as to protrude from a side of the case  24 , as viewed in a plan view in the direction DR 1  toward the installation surface  2 . That is, the antenna unit  92  protrudes from the side SD 1  of the substrate  40  and also protrudes from the side of the case  24  below corresponding to the side SD 1 . Thus, the drop in the sensitivity of the antenna unit  92  due to the electrically conductive case  24  can be restrained. Therefore, both of restraint on the deterioration in the accuracy of detection of the inertial sensor by accommodating the inertial sensor in the electrically conductive case  24  and improvement in the sensitivity of the antenna unit  92  can be achieved. 
     In the inertial measurement unit  10  having the configuration described with reference to  FIG. 12 , the wireless communication unit  90  and the antenna unit  92  need not necessarily be provided at the substrate  40  and may be provided, for example, at other substrates than the substrate  40 . For example, the wireless communication unit  90  and the antenna unit  92  may be provided at the substrate  48 , where the display unit  70  is provided, instead of the substrate  40 , where the processing unit  50  or the like is provided. Alternatively, various modified embodiments, for example, installing the wireless communication unit  90  and the antenna unit  92  at the top surface of the sensor unit  20 , can be employed. 
     The inertial measurement unit  10  has the substrate  40  provided with the wireless communication unit  90 , and the protection plate  160 . As described with reference to  FIGS. 1 and 2 , the substrate  40  is provided between the sensor unit  20  and the protection plate  160 . As shown in  FIG. 12 , the antenna unit  92  does not protrude from the protection plate  160 , as viewed in a plan view in the direction DR 1 . That is, the antenna unit  92  protrudes in the direction DR 6  from the side SD 1  of the substrate  40  and the corresponding side of the sensor unit  20  but does not protrude in the direction DR 6  from the corresponding side of the protection plate  160 . For example, the electrically conductive case  24  of the sensor unit  20  is not present below the antenna unit  92 , whereas the protection plate  160  is provided above the antenna unit  92  in such a way as to cover the antenna unit  92 . Providing the antenna unit  92  in such a way as not to protrude from the protection plate  160  as viewed in a plan view and providing the protection plate  160  in such a way as to cover the antenna unit  92  can prevent a situation such as where an unwanted impact is applied to the antenna unit  92 . For example, a situation where a finger of the user&#39;s hand or the like accidentally touches the antenna unit  92  and causes damage or the like to the antenna unit  92 , can be restrained. Therefore, the sensitivity of the antenna unit  92  can be improved by providing the antenna unit  92  in such a way as to protrude from the electrically conductive case  24  as viewed in a plan view, and the antenna unit  92  can be protected from an external impact by providing the antenna unit  92  in such a way as not to protrude from the protection plate  160  as viewed in a plan view. 
     The inertial measurement unit  10  includes the substrate  40  provided with the wireless communication unit  90 . The antenna unit  92  is provided in such a way as to protrude from the side SD 1 , which is a shorter side of the substrate  40 . Specifically, a communication substrate  94  is installed at the substrate  40 , where the processing unit  50  or the like is provided. The wireless communication unit  90  and the antenna unit  92  are provided at the communication substrate  94 . That is, a wireless communication IC as the wireless communication unit  90  is installed at the communication substrate  94 , and an inductor of a metal wiring is formed at a substrate part protruding from the side SD 1  of the substrate  40 , of the communication substrate  94 , thus forming the antenna unit  92 . The substrate part where the wireless communication unit  90  is installed and the substrate part where the antenna unit  92  is formed may be formed as a single substrate or may be formed as separate substrates. Providing the antenna unit  92  in such a way as to protrude from the side SD 1  of the substrate  40  in this way can reduce the risk of an unwanted impact being applied to the antenna unit  92 . For example, a situation such as where a finger of the user&#39;s hand touches the antenna unit  92  and applies an unwanted impact to the antenna unit  92  when the user holds the inertial measurement unit  10  on the two longer sides with the palm in contact with the top surface thereof, can be restrained. 
     As shown in  FIG. 12 , the wireless communication unit  90  is provided at the side SD 1 , which is a shorter side of the substrate  40 . Specifically, the wireless communication unit  90  is arranged along the side SD 1  in the direction DR 3  from the side SD 1 . The antenna unit  92  coupled to the wireless communication unit  90  is provided in such a way as to protrude in the direction DR 6  from the side SD 1 . Thus, the antenna unit  92  can be electrically coupled via a short path to the wireless communication unit  90  arranged at the side SD 1  of the substrate  40 , and the sensitivity of the antenna unit  92  can be improved by making the antenna unit  92  protrude from the side SD 1 . Therefore, the wireless communication unit  90  and the antenna unit  92  can be installed in a compact form at the substrate  40 , and improvement in the sensitivity of the antenna unit  92  can be achieved. 
     The inertial measurement unit  10  includes the substrate  40  provided with the wireless communication unit  90 , and the processing unit  50  provided at the substrate  40  and performing processing based on detection information from the inertial sensor of the sensor unit  20 . The wireless communication unit  90  transmits the information processed by the processing unit  50 . For example, when the processing unit  50  performs processing to process detection information from the inertial sensor, the wireless communication unit  90  wirelessly transmits, for example, the processed detection information to outside. When the processing unit  50  performs analysis processing on detection information from the inertial sensor, the wireless communication unit  90  transmits, for example, information about the result of the analysis processing to outside. Thus, instead of detection information from the inertial sensor itself, information resulting from predetermined processing performed on the detection information by the processing unit  50  can be wirelessly transmitted to outside by the wireless communication unit  90 . Therefore, an external device of the inertial measurement unit  10  need not perform the processing performed by the processing unit  50  of the inertial measurement unit  10 , and reduction in processing load and cost reduction or the like of the measuring system including the inertial measurement unit  10  can be achieved. 
     The handling of the detection information from the inertial sensor is difficult and needs expertise and therefore has the problem of poor user-friendliness. However, as the inertial measurement unit  10  transmits the information processed by the processing unit  50 , information that is easy for the user to handle can be transmitted and therefore user-friendliness can be improved. 
     As shown in  FIG. 12 , in the inertial measurement unit  10  according to this embodiment, the antenna unit  92  is provided in such a way as to protrude from the side SD 1  of the substrate, and the processing unit  50  is provided between the wireless communication unit  90  and the side SD 2  opposite the side SD 1 . The side SD 1  is the first shorter side. The side SD 2  is the second shorter side. For example, when the direction from the side SD 1  toward the side SD 2  of the substrate  40  is DR 3  and the opposite direction of the direction DR 3  is DR 6 , the antenna unit  92  is provided in the direction DR 6  from the wireless communication unit  90  in such a way as to protrude from the side SD 1  of the substrate  40 . The wireless communication unit  90  is provided in the direction DR 3  from the antenna unit  92 . The processing unit  50  is provided in the direction DR 3  from the wireless communication unit  90 . Thus, the antenna unit  92 , the wireless communication unit  90 , and the processing unit  50  can be efficiently arranged along the direction from the side SD 1 , which is a shorter side of the substrate  40 , toward the opposite side SD 2 . For example, the antenna unit  92 , the wireless communication unit  90 , and the processing unit  50  can be arrayed in this order along the direction from the side SD 3  to the side SD 4 , which is a longer-side direction of the substrate  40 . Thus, the efficiency of installation of circuit components at the substrate  40  can be improved. 
     The inertial measurement unit  10  includes the interface unit  100  for wired communication of data with outside. The interface unit  100  is arranged at the side SD 2 , which is a shorter side of the substrate. Specifically, the interface unit  100  is arranged along the side SD 2  in the direction DR 6  from the side SD 2 . The interface unit  100  is, for example, a circuit implementing a communication interface of UART, GPI, or SPI or the like. The provision of such an interface unit  100  enables transmission of information based on detection information from the inertial sensor to an external device and acceptance of a command from the external device, via a broadly used wired communication interface of UART, GPI, or SPI or the like. Since the interface unit  100  is provided at the side SD 2  of the substrate  40 , the antenna unit  92 , the wireless communication unit  90 , the processing unit  50 , and the interface unit  100  can be efficiently arranged along the longer-side direction of the substrate  40 . Thus, the efficiency of installation of circuit components at the substrate  40  can be improved. 
     As shown in  FIG. 12 , at least one of the mode changeover switch  80 , the reset switch  82 , and the measurement start switch  84  is provided at the side SD 3 , which is a longer side of the substrate  40 . Thus, the wireless communication unit  90 , the processing unit  50 , and the interface unit  100  can be arranged, using an area between the side SD 1  and the side SD 2 , which are the shorter sides of the substrate  40 , and the mode changeover switch  80 , the reset switch  82 , and the measurement start switch  84  can be arranged, using an area along the side SD 3 , which is a longer side of the substrate  40 . Therefore, an efficient installation layout can be achieved. Also, the inertial measurement unit  10  includes at least one fixing member  11 ,  12 ,  13  for removably fixing the sensor unit  20  and the substrate  40 , where the wireless communication unit  90  or the like is provided. Thus, as described above, the extensibility of the inertial measurement unit  10  can be improved, and a situation where an unwanted vibration or the like due to resonance or the like is transmitted to the inertial measurement unit  10  and adversely affects measurement can be restrained. 
     As shown in  FIG. 13 , in the inertial measurement unit  10  according to this embodiment, the sensor unit  20  has the sensor-side connector  26  at the surface facing the substrate  40 . That is, the connector  26  is provided at the top surface of the sensor unit  20 . The substrate  40  has a substrate-side connector  46  coupled to the sensor-side connector  26 , at the surface facing the sensor unit  20 . That is, the connector  46  is provided at the bottom surface of the substrate  40 . The connector  46  of the substrate  40  is electrically coupled to the connector  26  of the sensor unit  20 . Specifically, in the state where the sensor unit  20  and the substrate  40  are fixed together via the fixing members  11 ,  12 ,  13 , as shown in  FIGS. 1 and 2 , the connector  26  of the sensor unit  20  and the connector  46  of the substrate  40  are electrically coupled together. Thus, detection information from the inertial sensor of the sensor unit  20  can be communicated to the substrate  40  via the connectors  26 ,  46 . The processing unit  50  provided at the substrate  40  can perform processing based on the detection information from the inertial sensor. The display unit  60  provided at the substrate  40  can perform a display based on the detection information from the inertial sensor. The connector  26  is, for example, a male connector formed of a plurality of pin terminals. The connector  46  is, for example, a female connector to which a male connector can be coupled. 
       FIG. 14  is a state transition diagram explaining an operation of the inertial measurement unit  10  according to this embodiment. When the inertial measurement unit  10  is supplied with electric power and starts up, the inertial measurement unit  10  first shifts to the state of initialization processing. When it is detected that BT (Bluetooth (trademark registered)) is enabled, based on selection via the slide switch  86 , the inertial measurement unit  10  performs BT setup and then returns to the state of initialization processing on completion of the setup. When BT is enabled, wireless communication is disabled. Meanwhile, when a shift to a light display operation is detected, based on selection via the slide switch  86 , the inertial measurement unit  10  shifts to a light display mode. In the light display mode, the interface unit  100  shifts into a GPIO output mode, enabling light display via PATLITE (trademark registered) or the like using the inertial measurement unit  10 . 
     When BT being enabled or a shift to the light display mode is not selected via the slide switch  86 , the inertial measurement unit  10  assumes that a shift to a standby operation is detected, and therefore shifts to a standby mode. When learning is requested in the standby mode, for example, by a long press on the measurement start switch  84  or by a command, the inertial measurement unit  10  shifts to a learning mode and performs learning processing. In the learning mode, for example, a predetermined light-emitting element in the display unit  60  flashes on and off, or for example, the letters of “LEARNING” are displayed at the display unit  70 , thus notifying the user that learning is underway. Then, measurement is performed during a learning period in the learning mode. Based on the result of the measurement during the learning period, a measurement threshold as measurement criteria information for inertial measurement is found. The threshold thus found is stored into the memory  102 , which is a non-volatile memory. On completion of the learning processing, the inertial measurement unit  10  returns to the standby mode. When setup is requested in the standby mode, for example, by a command given from an external device or the like, the inertial measurement unit  10  performs various kinds of setup processing about the inertial measurement unit  10 . On completion of the setup, the inertial measurement unit  10  returns to the standby mode. 
     Also, when a request to start state monitoring is made in the standby mode by a press on the measurement start switch  84 , the inertial measurement unit  10  shifts to a state monitoring mode. In the state monitoring mode, the display unit  60  and the display unit  70  display the result of measurement. At this time, a press on the mode changeover switch  80  changes the display mode. Also, for example, when the measured value exceeds the threshold in the state monitoring mode, the inertial measurement unit  10  shifts to an alarm state and, for example, a light-emitting element for alarm in the display unit  60  flashes on and off. As the inertial measurement unit  10  shifts to the alarm state, log data is saved. When a request to stop state monitoring is made in the state monitoring mode or in the alarm state, for example, by another press on the measurement start switch  84 , the inertial measurement unit  10  returns to the standby mode. 
     In the inertial measurement unit  10  according to this embodiment as described above, the user first installs the inertial measurement unit  10  at a device or floor surface and presses the measurement start switch  84 . For example, the user holds the inertial measurement unit  10  with the palm in contact with the top surface of the inertial measurement unit  10  and presses the measurement start switch  84 , using a finger of the hand or the like. To cause the inertial measurement unit  10  to learn a threshold, the user long-presses the measurement start switch  84 , which causes the inertial measurement unit  10  to learn a measurement threshold. The user then presses the measurement start switch  84 . After pressing the measurement start switch  84 , the user waits for a predetermined measurement time. For example, the measurement time is a duration of 5 to 10 seconds. The length of the measurement time can be set. As the measurement time ends, a display via the LED as the light-emitting element in the display unit  60  or a display on the display panel  72  of the display unit  70  notifies the user of the result of the measurement. At this time, the user can switch between various display modes by pressing the mode changeover switch  80 . By pressing the measurement start switch  84  again, the user can stop the state monitoring mode and shift the inertial measurement unit  10  to the standby mode. In this way, with the inertial measurement unit  10  according to this embodiment, the user can carry out measurement by a simple operation. Since the display units  60 ,  70  display information based on detection information from the inertial sensor, the user can check the result of measurement via the display of information that is easy to understand, and this can improve convenience. The user can also check the result of measurement in various display modes by operating the mode changeover switch  80 . Also, since the inertial measurement unit  10  is provided with the wireless communication unit  90  and the antenna unit  92 , the inertial measurement unit  10  can wirelessly transmit information based on detection information from the inertial sensor, to an external device. In this case, since the antenna unit  92  is provided in such a way as to protrude from the main surface of the case  24  of the sensor unit  20 , wireless communication can be performed with high antenna sensitivity. 
     4. Sensor Unit 
       FIG. 15  shows a first configuration example of the sensor unit  20 .  FIG. 15  is an exploded perspective view of the sensor unit  20 . The sensor unit  20  shown in  FIG. 15  includes the sensor substrate  210  provided with at least one acceleration sensor as at least one inertial sensor, and the case  24  accommodating the sensor substrate  210 . In  FIG. 15 , the acceleration sensors  30 X,  30 Y,  30 Z detecting an acceleration in directions along the X-axis, the Y-axis, and the Z-axis, respectively, are provided at the sensor substrate  210 , as at least one acceleration sensor. The acceleration sensors  30 X,  30 Y,  30 Z are installed at the sensor substrate  210  in such a way that the main surfaces of the acceleration sensors  30 X,  30 Y,  30 Z are orthogonal to the X-axis, the Y-axis, and the Z-axis, respectively. The acceleration sensors  30 X,  30 Y,  30 Z are, for example, acceleration sensors using a quartz crystal vibrator and can detect an acceleration with higher accuracy than a MEMS (micro-electromechanical systems) acceleration sensor. Thus, a vibration or the like of a device or floor surface can be detected with high accuracy. In  FIG. 15 , the three acceleration sensors  30 X,  30 Y,  30 Z for detecting an acceleration on the three axes are provided at the sensor substrate  210 . However, various modified embodiments can be employed, such as providing one acceleration sensor for detecting an acceleration on one axis at the sensor substrate  210 , or providing two acceleration sensors for detecting an acceleration on two axes at the sensor substrate  210 . 
     Also, the processing unit  212  implemented by an ASIC, microcomputer or the like is provided at the sensor substrate  210 . For example, the processing unit  212  of the sensor unit  20  may execute a part or all of the processing carried out by the processing unit  50  of the inertial measurement unit  10 . At a second surface, that is, the back side of a first surface, which is the main surface of the sensor substrate  210  where the acceleration sensors  30 X,  30 Y,  30 Z are provided, the connector  26  formed of a plurality of connector terminals is provided. As described with reference to  FIG. 13 , the connector  26  of the sensor unit  20  is coupled to the connector  46  at the back side of the substrate  40  in the inertial measurement unit  10 . 
     The case  24  is formed of an electrically conductive material such as a metal and has the container  220  and the lid  222 . The sensor substrate  210  is accommodated in the accommodation space formed by the container  220  and the lid  222 . The container  220  and the lid  222  are fixed together and airtightly sealed by a fixing member such as a screw. A sealing member  224  as a buffer member is provided between the lid  222  and the sensor substrate  210 . 
       FIGS. 16 and 17  show a second configuration example of the sensor unit  20 .  FIG. 16  is an exploded perspective view of the sensor unit  20 .  FIG. 17  is a plan view of the sensor substrate  210 . The sensor unit  20  shown in  FIGS. 16 and 17  includes the sensor substrate  210  provided with at least one acceleration sensor and at least one angular velocity sensor, as at least one inertial sensor, and the case  24  accommodating the sensor substrate  210 . In  FIGS. 16 and 17 , the acceleration sensor  32  detecting an acceleration in directions along the X-axis, the Y-axis, and the Z-axis is provided at the sensor substrate  210 , as at least one acceleration sensor. Inside the acceleration sensor  32 , a sensor element detecting an acceleration in the X-axis direction and the Y-axis direction and a sensor element detecting an acceleration in the Z-axis direction are provided. These sensor elements are, for example, MEMS sensor elements. Also, various modified embodiments can be employed, such as providing individual acceleration sensors for the X-axis, the Y-axis, and the Z-axis, respectively, or providing an acceleration sensor for two axes or one axis of the X-axis, the Y-axis, and the Z-axis, at the sensor substrate  210 . In  FIGS. 16 and 17 , the angular velocity sensors  34 X,  34 Y,  34 Z detecting an angular velocity about the X-axis, the Y-axis, and the Z-axis, respectively, are provided as at least one angular velocity sensor. The angular velocity sensors  34 X,  34 Y,  34 Z are installed at the sensor substrate  210  in such a way that the main surfaces of the angular velocity sensors  34 X,  34 Y,  34 Z are orthogonal to the X-axis, the Y-axis, and the Z-axis, respectively. The angular velocity sensors  34 X,  34 Y,  34 Z are, for example, gyro sensors detecting an angular velocity, using a quartz crystal vibrator. Providing not only an acceleration sensor but also an angular velocity sensor at the sensor substrate  210  in this way enables not only detection of a vibration or the like but also detection of a tilt, attitude change and the like of a target object. In  FIGS. 16 and 17 , the three angular velocity sensors  34 X,  34 Y,  34 Z for detecting an angular velocity about the three axes are provided at the sensor substrate  210 . However, various modified embodiments can be employed, such as providing one angular velocity sensor for detecting an angular velocity about one axis at the sensor substrate  210 , or providing two angular velocity sensors for detecting an angular velocity about two axes at the sensor substrate  210 . 
     As shown in  FIG. 17 , at the first surface, which is the main surface of the sensor substrate  210  where the acceleration sensor  32  or the like is provided, the connector  26  formed of a plurality of connector terminals is provided. As described with reference to  FIG. 13 , the connector  26  of the sensor unit  20  is coupled to the connector  46  at the back side of the substrate  40  in the inertial measurement unit  10 . At the second surface, which is the back side of the sensor substrate  210 , a processing unit, not illustrated, implemented by an ASIC, microcomputer or the like is provided. For example, the processing unit of the sensor unit  20  may execute a part or all of the processing carried out by the processing unit  50  of the inertial measurement unit  10 . 
     The case  24  is formed of an electrically conductive material such as a metal and has the container  220  and the lid  222 . The sensor substrate  210  is accommodated in the accommodation space formed by the container  220  and the lid  222 . The container  220  and the lid  222  are fixed together and airtightly sealed by a fixing member such as a screw. The sealing member  224  as a buffer member is provided between the lid  222  and the sensor substrate  210 . 
     As described above, the inertial measurement unit according to this embodiment includes: a sensor unit having at least one inertial sensor; a display unit performing a display based on detection information from the inertial sensor; and a mode changeover switch. The mode changeover switch changes a display mode of the display unit. 
     According to this embodiment, the display unit provided in the inertial measurement unit can perform a display based on detection information from the inertial sensor of the sensor unit. Therefore, the work of checking the result of measurement can be simplified. Also, since the display mode of the display unit can be changed by operating the mode changeover switch, various demands about the display form of the result of measurement can be met. 
     In the embodiment, when a direction from the inertial measurement unit toward an installation surface for the inertial measurement unit is defined as a first direction and a direction orthogonal to the first direction is defined as a second direction, the mode changeover switch may have a moving part movable in the second direction. A movement of the moving part of the mode changeover switch may give an instruction to change the display mode of the display unit. 
     Thus, the user can give an instruction to change the display mode by a simple operation of moving the moving part of the mode changeover switch in the second direction, which is orthogonal to the first direction from the inertial measurement unit toward the installation surface. 
     In the embodiment, the moving part of the mode changeover switch, when not pressed, may protrude from a side of the sensor unit as viewed in a plan view in the first direction. 
     Thus, the display mode of the display unit is changed by a simple operation of pressing the moving part of the mode changeover switch protruding from the side of the sensor unit when not pressed. Therefore, user-friendliness can be improved. 
     In the embodiment, the inertial measurement unit may include a measurement start switch for starting measurement by the inertial measurement unit. 
     Thus, measurement by the inertial measurement unit can be started by a simple operation of operating the measurement start switch. Therefore, user-friendliness can be improved. 
     In the embodiment, when a direction from the inertial measurement unit toward an installation surface for the inertial measurement unit is defined as a first direction and a direction orthogonal to the first direction is defined as a second direction, the measurement start switch may have a moving part movable in the second direction. A movement of the moving part of the measurement start switch may give an instruction to start measurement by the inertial measurement unit. 
     Thus, the user can give an instruction to start measurement by the inertial measurement unit by a simple operation of moving the moving part of the measurement start switch in the second direction, which is orthogonal to the first direction from the inertial measurement unit toward the installation surface. 
     In the embodiment, the inertial measurement unit may include a memory, and a teach switch for giving an instruction to store measurement criteria information for inertial measurement into the memory. 
     Thus, the inertial measurement unit can be made to learn measurement criteria information corresponding to a measurement target, and measurement using the measurement criteria information can be realized. 
     In the embodiment, when a direction from the inertial measurement unit toward an installation surface for the inertial measurement unit is defined as a first direction and a direction orthogonal to the first direction is defined as a second direction, the teach switch may have a moving part movable in the second direction. A movement of the moving part of the teach switch may give an instruction to store the measurement criteria information into the memory. 
     Thus, the user can give an instruction to store measurement criteria information into the memory by a simple operation of moving the moving part of the teach switch in the second direction, which is orthogonal to the first direction from the inertial measurement unit toward the installation surface. 
     In the embodiment, the inertial measurement unit may include a substrate where the mode changeover switch is provided. 
     Thus, the mode changeover switch can be installed in a compact form in the inertial measurement unit. 
     In the embodiment, the inertial measurement unit may include at least one fixing member removably fixing the sensor unit and the substrate together. 
     Thus, the sensor unit and the substrate incorporated in the inertial measurement unit can be freely changed and the extensibility of the inertial measurement unit ca be improved. 
     In the embodiment, the inertial measurement unit may include a first substrate and a second substrate, as the substrate. The mode changeover switch may be provided at the first substrate. The display unit may be provided at the second substrate. The first substrate may be provided between the sensor unit and the second substrate. 
     Thus, when the mode changeover switch provided at the first substrate is operated, the display mode of the display unit provided at the second substrate changes. Since the mode changeover switch is provided at the first substrate provided between the sensor unit and the second substrate, the operability of the mode changeover switch can be improved. 
     In the embodiment, the display unit may display, in a first display mode, a result of determination based on a first determination criterion, and in a second display mode, a result of determination based on a second determination criterion, as a result of determination based on the detection information. 
     Thus, as the user operates the mode changeover switch, the result of determination about measurement is displayed at the display unit, based on different determination criteria. The result of determination based on various determination criteria can be presented to the user. 
     In the embodiment, the first determination criterion may be a determination criterion of VC (vibration criteria), and the second determination criterion may be a determination criterion set by a user. 
     Thus, the display mode can be switched between the first display mode, in which the result of determination based on the VC determination criterion is displayed, and the second display mode, in which the result of determination based on the determination criterion set by the user is displayed, via the mode changeover switch. 
     In the embodiment, a unit of information displayed based on the detection information may be changed via the mode changeover switch. 
     Thus, the measured value can be displayed in various units to the user via the operation of the mode changeover switch. Therefore, user-friendliness can be improved. 
     In the embodiment, the inertial measurement unit may include a processing unit performing processing based on the detection information. The processing unit may perform analysis processing on vibration information about a detection target. The display unit may display information about a result of the analysis processing. 
     Thus, as the processing unit performs analysis processing on detection information from the inertial sensor and the display unit displays information about the result of the analysis processing, the user can easily grasp the vibration state of the detection target. 
     In the embodiment, the sensor unit may include a sensor substrate provided with at least one acceleration sensor as the at least one inertial sensor, and a case accommodating the sensor substrate. 
     Thus, the display unit provided in the inertial measurement unit can perform a display based on detection information from the acceleration sensor provided at the sensor substrate of the sensor unit. Therefore, the work of checking the result of measurement can be simplified. 
     In the embodiment, the sensor unit may include a sensor substrate provided with at least one acceleration sensor and at least one angular velocity sensor, as the at least one inertial sensor, and a case accommodating the sensor substrate. 
     Thus, the display unit provided in the inertial measurement unit can perform a display based on detection information from the acceleration sensor and the angular velocity sensor provided at the sensor substrate of the sensor unit. Therefore, the work of checking the result of measurement can be simplified. 
     The embodiment has been described above in detail. However, a person skilled in the art will readily understand that various modifications can be made without substantially departing from the new matters and effects of the present disclosure. Therefore, such modifications are understood as included in the scope of the present disclosure. For example, a term described along with a different term having a broader meaning or the same meaning, at least once in the specification or drawings, can be replaced with the different term in any part of the specification or drawings. Any combination of the embodiment and the modifications is included in the scope of the present disclosure. The configuration, operation and the like of the inertial measurement unit are not limited those described in the embodiment and can be carried out with various modifications.