Optimum gap according to magnet material and size

The following table indicates the magnetic field detection range of EM-3242.

Below are the optimum gap dimensions calculated for the following disc magnets (polarized radially)
The gap here refers to the distance between the magnet and the sensor package.

<Magnet conditions>

• Material
  1.Neodymium magnet
  (Residual magnetic flux density : Br = 1130 mT)
  2.Ferrite magnet
  (Residual magnetic flux density : Br = 340 mT)
• Diameter : 5 mm, 7 mm, 10 mm
• Thickness : 1 to 5 mm
• Magnetizing direction: Radial

The following are examples of calculation to obtain a gap providing 30 mT flux density on the sensor face.
The gap (*1) here refers to the distance between the magnet bottom and the package surface.

As indicated above, the optimum gap becomes larger as the disc magnet is larger in diameter as well as thickness. Besides, a larger residual magnetic flux density offers a larger optimum gap.You can choose an optimum size of magnet according to your application.

Relationship between gap and magnetic flux density applied to sensor (example of calculation)

<Calculation conditions>

• Magnet size: 7.0 dia. x t2.0 mm
• Magnet material: Neodymium (Residual magnetic flux density: Br = approx. 1130 mT)