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Magnetic Field Calculations

Magnetic flux density, in gauss or tesla, can be calculated at any distance from the end of a magnet. Results are for the field on-axis, at a distance "Z" from a pole of the magnet. For magnets that are relatively large compared with the sensor (e.g., Hall chip), measurements should agree very closely to the calculations. Where the sensor is large relative to a small magnet, the measurement can be deviate by several percent as the measurement represents the average flux density over the cross-sectional area of the Hall sensor.

Recall also, that a magnetic field is a vector: it has both a magnitude and a direction. A Hall sensor chip provides the magnitude of the field perpendicular to the plane of the chip - - it is necessary to ensure the Hall sensor chip is perpendicular to the magnetic field. This can be checked by rotating the sensor to achieve the maximum reading.

These calculations are most appropriate for "square loop" (intrinsic curve) or "straight line" (normal curve) magnetic materials such as ferrite (including bonded ferrite), neodymium-iron-boron and samarium cobalt magnets. When used for other materials such as alnico magnets, accuracy will depend greatly upon the size and shape of the magnet, with longer magnetic length providing better results.

Field Calculations for Cylindrical Magnets

Field Calculations for Rectangular Magnets

Accuracy Statement
While we make every effort to ensure that the information contained in these documents is complete and accurate, we make no warranty regarding this. Please see our disclaimer statement. We would appreciate your input regarding corrections, additions and suggestions for improvement (e-mail us).

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