How to select magnets in hall position sensors

With the vigorous development of the electronic industry, the position detection of some structural components slowly changes from the original contact measurement to the non-contact measurement through the Hall position sensor and magnet. How can Horizon choose a suitable magnet according to Horizon products and structure? Here Horizon do some simple analysis.

First, Horizon need to determine the magnet material. At present, samarium cobalt magnet and neodymium iron boron are widely used in hall position sensor. The main difference between the two magnets is that based on the same volume NdFeB magnet are stronger than samarium cobalt magnets; the thermal excursion of samarium cobalt is smaller than that of Nd-Fe-B; the oxidation resistance of samarium cobalt is stronger than that of Nd-Fe-B, but generally there is a coating on the outside of the magnet, which can solve the problem of oxidation; the samarium cobalt magnet has better temperature resistance than NdFeB magnet, but temperature resistance value for both magnet materials can reach more than 200 ℃. Therefore, when selecting the type of magnet, Horizon should evaluate it in combination with cost performance, working temperature and working environment. In general, NdFeB may be used more, mainly because it has the best magnetic field characteristics. However, when working in a wide temperature range, it is recommended to choose samarium cobalt magnet because of its small thermal drift.

In addition, Horizon need to determine some basic parameters of the magnet. According to the test position information and the moving direction of the object, Horizon determine whether the magnetization direction of the magnet is diametrical or axial. In addition, it is determined whether to select a square magnet or a cylinder magnet according to the installation structure. Of course, sometimes Horizon need to customize the shape of the magnet according to the structure. There is another factor of requirement about magnet flux, which has always been Horizon concern in magnet selection. In fact, Horizon need to analyze it in the following two aspects:

1. The magnetic field strength induced by the hall position sensor itself and the induced magnetic field range in each direction will be clearly marked in the sensor data book.

2. The distance between the magnet and the sensor itself is generally determined by the product structure. According to the above two aspects and the magnetic field change curve in the figure below as an example, Horizon can determine the magnetic field strength of the required magnet.

Finally, Horizon must need to understand that it does not mean that as long as the magnetic field falling on the range requirements of the sensor, the magnet can be as far away from the sensor. Although the sensor itself has calibration function, Horizon need to understand that when the magnet is too far from the sensor, the distribution of the magnetic field itself is difficult to ensure linearity or close to linearity. This means that with the change of position and the nonlinear distribution of the magnetic field itself, the sensor measurement will become complex and the calibration will become very complex, so that the product does not have reducibility.

The above is just a simple analysis of magnet selection in Hall sensor applications. Horizon hope it will be helpful to people. If people have other questions during the development process, please contact Horizon, Ningbo Horizon Magnetics. Horizon can make further communication and provide people with technical support.

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Company Name: Ningbo Horizon Magnetic Technologies Co., Ltd.
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