The controller divides a display of the display component provided to the main body case into a first display area that is disposed on a sensor mounting component side and displays measurement values, and a second display area that is disposed on the opposite side from the sensor mounting component side and displays input buttons. When the acceleration sensor has detected that the orientation of the main body case is inverted in a horizontal direction, the controller rotates a display of the first display area and a display of the second display area 180 degrees within each of these areas.