A wide range of magnets with different characteristics are available in the market, and almost all sizes and shapes can be achieved. To activate the reed switch (reed switch), a magnet (magnetic field) is required, and different magnet materials will have positive or negative polarity characteristics, depending on the size, shape, and environmental factors of the magnet. Cylindrical, rectangular, ring-shaped and dish-shaped magnets are more popular shapes. According to the diversification of requirements, magnets can be magnetized by different methods.
At the same time, the magnetic force and magnetic flux density of each kind of magnet material are different. In addition to size and raw materials, there are other factors that can affect the strength of the magnet. These factors include the installation location, the installation environment, and other magnetic fields that can affect the interaction of the reed sensor and the magnet. When using a magnet to activate a reed sensor or a switch, the temperature of the installation environment also needs to be taken into consideration (this applies also to storage). High temperatures can lead to irreparable damage and have a large impact on the magnetic and long-term stability. In this regard, Alnico magnets can be used in operating environments up to 450 °C.
The degaussing characteristics of magnets are divided into reversible and irreversible types. Special attention should be paid to avoiding impact, vibration, magnetic fields that are too strong or too close, and high temperatures. All of these factors can affect magnetic field strength and long-term stability in varying degrees. Magnets are more suitable for being mounted on moving parts. The combination of a professional reed switch (reed switch) and a magnet enhances the functionality of the entire reed sensor system.
The raw materials of AlNiCo magnets are nickel-aluminum alloy, cobalt, iron and titanium. Made using a sintered casting method. After sintering, it needs to be ground to achieve the best size. According to its characteristics, the optimal size is significantly longer than the diameter of the magnet itself. When mating with a reed switch/reed sensor, we recommend that the length/diameter ratio of the magnet is greater than four. Alumino-cobalt magnets have very good temperature stability, but the disadvantage is that their raw materials are expensive.
Rare earth magnet
Rare earth magnets such as Samarium Cobalt and Neodymium Iron Boron have the highest energy product and are least susceptible to demagnetization. Here we use different magnets to compare under the same energy conditions:
Ferrite = volume 6 cm3
AlNiCo = volume 4 cm3
Samarium Cobalt = Volume 1 cm3
Neodymium iron boron = volume 0.5 cm3
Both of these magnets are manufactured by a sinter process. Because of their low strength and fragility, they can only be processed by grinding. Operating temperature range up to 250 °C, and can make a very fine magnet. The disadvantages of this magnet are the high price of raw materials and the limited amount of rare metals. The presence of magnets of different shapes, sizes, and magnets gives the reed sensor/switcher greater creative space to help discover the sensors that perform best for each application.
Raw materials for the manufacture of hard ferrite magnets include iron oxide and antimony oxide or antimony oxide. These raw materials are mixed together and are usually sintered in advance to generate magnetic force. The frit mixture is then crushed and the resulting powder is compressed (wet or dry) in a magnetic or non-magnetic environment and finally re-sintered. Processes can only be processed by grinding. Because of the low cost of raw materials, ferrite magnets are the cheapest of all magnet types. Ferrite has a good insulation effect, not easy to demagnetize and not easily corroded. A long, thin profile is the most suitable, while a round magnet is easier on the process. Disadvantages are its fragility and low tensile strength, its strength and brittleness are similar to pottery, in addition its limited temperature resistance and low magnetic energy product.
Magnet handling precautions
The attraction of a strong magnetic force can cause skin injuries. Keep a safe distance between each magnet and all other ferromagnetic objects.
Strong collision of magnets may generate debris, so protective gloves and protective glasses are required
When grinding rare earth magnets, the magnet powder is flammable and must be treated in water
Strong collision of magnets can cause sparks, so it is prohibited to process in flammable environments
Strong magnetic fields can interfere with electronic devices such as data storage media, and do not bring magnets close to regulators, navigation instruments, disks, plug-in boards, etc.
When airfreight needs to be reported as much as possible
Radiating energy or adding the same polarity can reduce magnetic force
Do not exceed the specified maximum operating temperature during operation