Horizon Magnetics are about to help sensor manufacturers as well as end-users in industries to design, optimize and choose the right magnet for any Hall effect sensor.
A Hall effect sensor is a magnetic sensor based on the Hall effect, which was discovery by American physicist Edwin Herbert Hall in 1879. Hall effect is a process in which a transverse electric field is developed in a conductor when the conductor carrying an electric current is placed in a magnetic field that is perpendicular to the current. The basic relationship of transverse electric field Vhall is:
In the formula, Rh - Hall coefficient decided by the properties of the conductor; Ihall- Current passing through; B - Magnetic induction intensity perpendicular to I; d - thickness of the conductor
From the Hall effect principle, we know that the Hall effect sensors can not work without magnetic field, which is mainly supplied by a permanent magnet conveniently and economically. Hall effect sensors can be used to detect magnetic fields and their changes, and can be applied in various situations related to magnetic fields. The output voltage signal of a Hall sensor is decided by the magnetic field, which is affected by the polarity, shape, size and magnetic field strength of magnets. Precise design and selection of magnets can improve the performance and response characteristics of Hall effect sensors.
Although there are several different types of sensor magnet materials, currently Neodymium magnets are often used because of their higher magnetic properties and Samarium Cobalt magnets are another popular choice of magnetic material due to their high magnetic performance with perfect temperature stability—especially at temperatures between 150° C and 180° C.
By utilizing the Hall effect, various types of sensors can be designed and manufactured. From the Hall effect formula, we find this principle works based on four factors, Hall voltage, conductor, electric current, and magnetic field. Moreover, Hall voltage varies linearly with electric current and magnetic field strength. Therefore the hall voltage change can be used to measure the change of electric current or magnetic field. Magnetic field can be also artificially set on the object being tested to work as the carrier of the information being tested. Through it, many non electric and non magnetic physical quantities such as force, torque, pressure, stress, position, displacement, velocity, acceleration, angle, angular velocity, rotation speed, and the time when the working state changes are converted into electrical quantities for detection and control.
Hall effect sensors are widely used due to their many advantages, such as sturdy structure, small size, light weight, long lifespan, easy installation, low power consumption, high frequency, vibration resistance, and resistance to pollution or corrosion from dust, oil, water vapor, and salt spray. Hall analog sensors have high accuracy and good linearity; Hall digital sensors have no contacts, no wear, clear output waveform, no jitter, no rebound, and high position repeatability accuracy.
Contact-free Hall effect sensing is an excellent way to provide sensitive and accurate measurement and control in many systems. We have been supplying Hall Effect sensor manufacturers with high quality rare earth magnets for following reasons:
Over 20 years experience in rare earth magnet production, working with customer engineers from the concept to supply customized magnets to meet their unique requirement, stable rare earth magnet supply of quality, quantity and delivery assured.
The most strength is our experience in supplying quality rare earth magnets for Hall effect sensor application. We work with sensor factories to design and choose the right magnet from types of materials, grades, shapes, sizes, polarity, etc. Generally, Hall effect sensors do not have very high requirements for magnets, as long as the magnet can generate sufficient magnetic field to induce the Hall sensor. However, some special application scenarios require Hall sensors with more stable and accurate magnetic fields, it may be necessary to choose some better quality magnets to ensure the performance and accuracy of the sensor. In addition, if the temperature of the magnet changes significantly, it will affect the output signal of the Hall sensor and may even cause measurement errors in the sensor. When selecting a correct magnet for a Hall effect sensors, we should consider many factors like switch type, desired switching characteristic, switching distance, way of movement, dimensions/tolerances/ weight, temperature range, surrounding materials, mounting options, existing space, etc.
Hall Effect is activated by the magnetic field, while the magnitude of the field is impacted by a number of factors such as magnetic material, magnet size, proximity of the sensor to the permanent magnet, etc. Our knowledge and experience gives a general guidance for reference:
Air gap: Magnetic flux density is inversely proportional to the square of the distance to the magnet. As a result, there can be a very dramatic change to the field strength as a result of initially small changes in distance.
Movement fashion: The magnetic flux density change is different between the pole of magnet movement in head on fashion and slide-by fashion.
Magnetic material: Based on the same magnet size and polarity, Neodymium magnet and Samarium Cobalt magnets generate much higher magnetic flux density than that of Alnico and Ferrite magnets.
Polarity and shape: They can affect the output signal of Hall sensors. The N and S poles of the magnet have different potential difference directions on both sides of the Hall effect sensors.
Cost: Higher grade magnets and larger magnets are more expensive. Revised material, shape, size or polarity of a magnet may reach required magnetic flux density with lower cost.
Temperature stability: Hall effect sensors normally work well at -40° C and 150° C, so Neodymium magnet can work well in this temperature range, but Samarium Cobalt magnet has much better temperature stability than that of Neodymium magnet.
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