Sensor device system

A sensor device system comprising:

• a sensor device attachable for use to a measuring instrument and configured to contactlessly acquire a measurement value measured by the measuring instrument,
• the measuring instrument including
• a scale plate marked with a scale;
• a shaft member that moves rotationally around an axis perpendicular to a plate face of the scale plate;
• a pointer that moves rotationally around the axis together with the shaft member and indicates the scale;
• and
• a magnet that moves rotationally around the axis together with the shaft member, the pointer including
• an axial portion attached to the shaft member;
• and
• an indicating portion extending radially outward from the axial portion and pointing to the scale as viewed in an axial direction,
• the magnet having one each of an N pole and an S pole disposed in a circumferential direction of the shaft member,
• the sensor device including
• a sensor circuit;
• and
• a case accommodating the sensor circuit,
• the sensor circuit generating a magnetic pole boundary direction value by detecting a magnetic pole boundary direction parallel to an interface between the N pole and the S pole, and generating a meter reading value by correcting the magnetic pole boundary direction value with a correction value, and
• the correction value being calculated based on an extension direction of the pointer and an angle formed by the magnetic pole boundary direction and a reference direction of the magnetic pole boundary direction.