In reed sensor applications it is important to understand the exact pull-in and drop-out fields. This information then allows one to properly position the magnet and sensor well within appropriate guard bands and avoid any tolerance issues. Most users have no idea what the actual magnetic field looks like. Presenting the fields in a three dimensional view gives the user a better chance to have an optimized design. This will help define adequate operate and deactivate points. Additionally, this will insure operation takes place well within the magnetic envelopes to avoid tolerance issues. We can insure acceptable hysteresis between the operate and deactivate points. We can optmize the sensor and magnet costs.
Magnetic mapping is the method of incrementally measuring the pull-in and drop-out points by either holding the sensor stationary while moving the magnet or vice versa. The movement must be carried out in all three dimensions. Software is then used to bridge all the points allowing the magnetic field to be visualized in three dimensions.
An electromagnet is a magnetic field generated when a coil of wire is formed in a cylindrical shape. The magnetic field will be uniform through the entire length of its inner opening.
Ferromagnetic is the property of a material that allows it to become magnetized permanently or temporarily when in the influence of a magnetic field generated by a permanent magnet or an electromagnet.
A uniform magnetic field can be made by making a relatively long cylindrical coil. Once current is flowing through the coil a uniform magnetic field will exist all along the inside of the coil. This is not true at the very ends of the coil. Helmholtz coils can be bought for the very reason of supplying a uniform magnetic field. In either case, the uniform magnetic fields allow for calibration.
Yes there is and it clearly depends on the type of magnet. The length to diameter is the key ratio.
- Alnico 5 is 5:1
- Alnico 8 is 3:1
- Ferrites are 1:1
- Rare earth is 1:1
Using a Helmholtz coil makes it very easy to calibrate magnetic fields in either ampere turns (AT) or milliTesla (mT).
A Helmholtz coil is actually two concentric coils mounted parallel to each other and when energized by passing a current through them they will produce a uniform magnetic field between the two coils.
Generally winding fine copper wire in a cylindrical configuration will create a magnetic field internal to the cylinder, when a current is passed through the copper wire.
Artificial magnets can be created by doping iron, nickel, and/or cobalt with other elements. Doping with rare earth materials has been particularly successful, producing very strong magnets.
The magnetic force is generated at the subatomic level and the energy comes from heat. Any temperature above absolute 0 (-273°C)
A dipole is the basic building block of a magnetic field. A dipole is the magnetic effect from a single atom. When taken many million times over, one has a magnetic field being generated from a magnet.
1.铝镍合金 – 稳定和最佳温度效应
Magnetic is a force produced at the subatomic level. It is caused by electrons spinning and also rotating around the nucleus of the atom.
When metal is subjected to a very high temperature bath, that process is called annealing. The temperature is slowly increased to a max temperature where it is stabilized for a period of time, and then the temperature is slowly reduced back to room temperature. This process will leave the metal in its softest state. For a reed switch this is very important because this point is also where the nickel/iron leads have near zero magnetic retentivity. This means when the reed switch contacts are subjected to a magnetic field and then the magnetic field is removed, there will be no residual magnetism on the leads.
A magnet and reed switch can be turned into a temperature sensor by using a magnet that has a certain curie temperature for the temperature you want to sense. When that curie temperature is reached the magnet loses its magnetic properties whereby the reed switch contacts open. When the temperature drops below the curie temperature, the reed contacts will close.