Magnetic Field Strength CalculationsMagnetic field strength, in gauss or tesla, can be calculated at any distance from the end of a magnet. Results are for field strength 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 it 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" or "straight line" 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.
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