What is the Hall Effect?

The Hall Effect is an important principle in science. The effect shows that a semiconductor or conductor that has a current flowing through it in one direction was brought into contact perpendicular with a magnetic field it was possible to measure voltage at right angles to the current path. The Hall Effect is a result of interaction between charged particles, such as electrons, with other fields, such as electrical or magnetic fields.

The Hall Effect occurs because of the nature of the current that is in the conductor. The current has a number of different carriers for a charge, including ions and electrons, and sometimes holes. If there is a magnetic field there, but it is not parallel to the moving charges, the charges will experience a different effect called the Lorentz force. When introduced to a perpendicular component, the charges will act differently and will not follow a straight path. Instead, they will have a curved path between collisions, and this means that those charges will actually accumulate on one face of the material.

The opposite charges are then going to be on the opposite side of the material. This will result in a disproportionate charge distribution. This can create an electrical field that stops or slows the passage of charges, thus providing a steady electrical potential – as long as there is some charge flow. The discovery of the Hall Effect threw some people into confusion, as it was so much different from what anyone has seen or theorized before.

The Hall Effect can be quite helpful for those who are in need of measuring the carrier density or the magnetic field. It’s easier to differentiate between the negative and positive charges because they take different positions.

The Hall Effect is important because it was the first time anyone was able to prove that the currents that pass through metals are actually carried by electrons rather than protons.

Who Discovered the Hall Effect?

Edwin Herbert Hall, from whom the effect gets is name, was a physicist who, in 1879 discovered the principle. At the time, he was working on his doctorate as Johns Hopkins University in Maryland. This was quite an accomplishment, and it meant a lot for science at the time. In fact, the electron wasn’t even discovered for another 18 years. Hall was a bit ahead of the game.

How is the Hall Effect Used in Semiconductors?

If a semiconductor is carrying a current, and it is in a magnetic field, the charge carriers in the semiconductor are going to experience a “force in direction perpendicular to both the magnetic field and the current”. When balanced, there is going to be a voltage at the semiconductor edges. As you can see, the Hall Effect is going to be a bit more complicated when it comes to semiconductors than it is with regular conductors.

Different Types of Hall Effect

You will find different types of Hall Effect in different circumstances and under different conditions.

  • Quantum Hall Effect – one can observe the Hall Effect on a quantum level when there is a large and strong magnetic field, and when there is a very low temperature
  • Spin Hall Effect – the Spin Hall Effect “consists in the spin accumulation on the lateral boundaries of a current carrying sample”. In the case of this effect, there is no need for a magnetic field.
  • Quantum Spin Hall Effect – this is a combination of the two above types of Hall Effect, and it is something that has only recently been observed.
  • Anomalous Hall Effect – also known as the extraordinary Hall Effect, this depends on the magnetization of the material and will often have a much larger result than a traditional hall effect. This can be extrinsic or intrinsic
  • Hall Effect in Ionized Gases – it is even possible to experience the Hall Effect in ionized gases, or plasma. It is a bit different from what one generally is going to see in solids.

What Applications Use the Hall Effect?

The Hall Effect is useful in a variety of different applications today. Devices called Hall Probes are useful for measuring magnetic fields, as well as to inspect materials. They utilize the principles of magnetic flux leakage in order to do this. One of the hallmarks of the Hall Effect devices is the fact that they only produce a low signal, and they are going to require amplification to be of any use. That’s why they were only useful in lab experiments in those first years after the discovery.

However, things are different today, and you will find that it’s now easier to afford the cost of integrated circuitry that makes that Hall Effect more useful for far more applications. In fact, quite a few of the devices that you will now see on the market as Hall Effect Sensors have a sensor included as well as an integrated circuit amplifier. Advances in these areas are making the products better, and even more efficient.

One of the great things about the sensors today, and something that they have as a bit of an advantage over the other options is that they are not going to fall prey to dirt, debris or water, as long as they are made well. The sensors will have three terminals on them. Sensor voltage is for two of the terminals, while the third provides a voltage that is similar to that of the current that you are trying to sense and measure. Because you are not going to have to deal with the same resistance, you will find this to be yet another advantage of using sensors that will be able to measure the Hall Effect.

Hall Effect sensors are available from quite a few different manufacturers today, and you will find that you can use them for a variety of different purposes. For example, many are using them in measuring rotating speed – such as for wheels, speedometers, and even ignition systems that use electricity. They are also un use with fluid flow sensors, pressure sensors, and current sensors. Some of the things that you will recognize that make use of the sensors include smart phones, electric air and paintball guns, and certain GPS units.

Analog multiplication , which is something necessary for most of the small digital computers that are around today, need to make use of a voltage sensing Hall Effect device as well. Others are able to sense current, as well as position and motion. Hall Effect devices are also useful for ignition switches, and a host of different industrial applications. For example, you will find that there are Hall Effect devices used to help control hydraulic valves. These replace the mechanical levers in many machines including large trucks for mining, cranes, scissor lifts, and more.

One of the most interesting areas where you will find the Hall Effect devices in use is in outer space. A Hall Effect Thruster, or HET, is a low power device that some spacecraft are using for propulsion once they achieve orbit or go further into space. With this technology, an electrical field will ionize and accelerate the atoms. The radial magnetic field on the thruster magnets will trap electrons and create an electrical field thanks to the effect. Neutral propellant enters the chamber to become ionized by the trapped electrons, and then they eject from the thruster as quasi-neutral plasma. This is what is going to create the thrust and movement for the spacecraft.

What are Hall Effect Switches?

A Hall Effect switch is magnetically activated and uses a Hall generator, trigger circuit, and transistor amplifier, and is usually found on a silicon chip. It is a Hall Effect sensor, really. The only difference is that it has an on and an off switch.

This digital off and on switch, used with a sensor, can change the effect of the device and application. The sensors, combined with switches, are useful for many different industries when it comes to measuring movement of electromagnetic devices. For example, in brushless DC motors, the sensor’s voltage is going to peak two times for each revolution. This will case the switch to turn on and off – or to change the current’s direction. You can see these in action on hard disk drives.

Of course, you are also going to find some disadvantages when it comes to using these switches and the Hall Effect. One of the first things that one will likely notice is that magnetic flux has the potential to affect the sensors. What does this mean? It means that you will sometimes be getting inaccurate readings. Another issue that people had in the past was the fact that the readings were tiny and needed amplification, which we’ve already discussed.

Who Produces Hall Effect Switches?

Quite a few different companies today are making these switches. Some of the most prominent makers include:

  • APEM – the company has been around since 1952, and they’ve become one of the top manufacturers of man and machine interfaces in the world. They are currently in 11 different countries and have more than 130 different distributors. They manufacture products for medical use, communications, transport, industrial automation, and much more.
  • OTTO – this company has been around for more than 50 years, and they have been designing and creating products for a host of unique applications. The company is in Carpentersville, Illinois and has worldwide recognition for the quality of their products as well as the innovation they bring to the table. OTTO makes some high quality switches for the Hall Effect that have digital and analog output options. They are sealed and lighted and offer high performance. You could choose from snap action, rocker, pushbutton, rotary and toggle switches.
  • Ultra Electronics – the company, located in the UK, is internationally known for the quality of their work no matter what type of devices or service they are offering.
  • Lucas Stability – here is another high quality and respected company in the UK that is able to offer Hall Effect switches, as well as a number of other products and devices that are useful for a number of different industries and business areas. The devices service a number of different industries.
  • Cherry – Walter Cherry established the company in 1953, and it has been going strong ever since. The company prides itself on technological innovation, and you will find that there are going to be some great products that they offer. They are proud of their capabilities and their customer service.
  • CH Products – here is another company with a long history. CH products has been in the business of creating high quality Hall Effect control devices for a number of years. Today, they manufacture fingertip joysticks for Hall Effect control, trackballs, handgrip controllers, and more. The products the company makes are in use in many different industries around the world including camera controls, medical instruments, vehicles, robots, electric wheelchairs, consumer entertainment, and industrial automation. The company is quite innovative and is able to offer reliable products.

If you find that you need to purchase materials that will help you create, measure, or utilize the Hall Effect in any way, it’s very important that you choose the right company for the job. You might find that you need to deal with more than one company for all of the different components that you need, or a company may in fact be able to provide you with all of the tools you must have. Always make sure you know the quality of the materials you are buying, the reputation of the company, as well as how you are going to be utilizing all of those components.

As you can see, the Hall Effect, even though it might seem like a minor discovery, is actually one of the most important discoveries when it comes to physics and the application of electronics. Things today would undoubtedly be much different if the discovery of the effect did not take place when it did.

Leave a comment

Your email address will not be published. Required fields are marked *