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Magneto-Electric Rotation Detector Frequently Asked Questions

Question number FAQ-0855

Precautions when installing multiple MP-981 units.

(Question supplement)Four MP981 units were installed on one gear. The fixture material is SUS400. The outer two units operate even with a gap of more than 1mm with the gear, but the inner two units do not operate with a gap of 1mm; they only operate with a gap of 0.8mm. Why is that?

To conclude, SUS400 is a magnetic material, so please change it to a non-magnetic material.


The MP-981 has a magnet in the tip. It forms a magnetic circuit between the MP and the valleys of the gears, detecting changes in that magnetism.
Therefore, if magnetic materials are used for installation, the magnetism between the gears tends to be weakened, resulting in reduced sensitivity.
In practice, most cases are fixed with iron materials, but when using multiple units, adjustments may be necessary to bring the gaps closer due to the magnetic influence between the MPs.


Please refer to the list of cautions for use. For details, please refer to the instruction manual.


  • The detection gear should be made of ferromagnetic material, within modules 1 to 3, with a tooth width of 3mm or more.
  • The MP981 installation fixture is made of non-magnetic materials and is fixed in place to prevent movement due to vibrations.
  • Install the gear to align with the MP positioning mark.
  • When installing multiple MPs, maintain a distance of at least 35mm.
  • In a strong magnetic field (in environments with magnetic changes), the magnetic circuit can easily become unstable, and as a result, it may not be detectable.
    (For large AC motors, please consider installing them in positions less affected by the magnetic field.)
  • It is not suitable for precise position detection.
    (When detecting protrusions, there is variation in the relationship between the protrusion position and the signal.)

    • Last updated: 2000-04-10