The Hall Effect and It´s Impact on Modern Technology

Cylinder sensors , Know-how , Linear sensors , Rotary sensors , Technologies
Wednesday 5 May 2021

The Hall effect is a principle that generates a voltage across a conductor when exposed to a magnetic field perpendicular to the direction of current flow. This effect forms the basis for Hall-effect sensors. Recent advancements have expanded these sensors into two- and three-dimensional variants, greatly enhancing their applications in various industries.

The Discovery

The Hall effect, named after physicist Edwin Hall who discovered the phenomenon in 1879, occurs when a conductor carrying current is placed perpendicular to a magnetic field, generating a voltage difference across the conductor. This voltage is known as the Hall voltage.

In the absence of an external magnetic field, charges within the current will flow in a straight line through the conductor. However, in the presence of a magnetic field, the charges flow is curved by a force. This force is called the Lorentz force. The potential difference created by these curved charges is the Hall voltage.

Hall Effect Sensors

Although Hall’s discovery led to successful experiments, the practical use of the Hall effect was initially limited. This changed with the advancement of silicon semiconductors in the 1960s. The first Hall effect sensors combined Hall-effect sensor elements with amplifiers, leading to the development of the first integrated circuit Hall switch.

Today, Hall effect integrated circuits are available with a wide variety of characteristics for different applications. Both the Hall-effect IC (the sensor chip) and Hall-effect transducers are commonly referred to as Hall-effect sensors. Despite the capabilities of modern Hall effect ICs, they are often integrated with transducers that include a voltage regulator, EMC safeguards, output calibration, a mechanical enclosure for the sensor and magnet, an electrical connector, and so on.

To learn more about sensors and transducers, read our article explaining the different terminology.

Flux and Magnet Orientation

Hall-effect sensors are influenced by two magnetic properties: magnetic flux density and polarity. Magnetic flux* refers to the field strength that affects the sensor, and the polarity of the magnet determines the direction of the flux, as it always travels from north to south.

The correct configuration of the sensor, magnet, and orientation is crucial for accurate measurement, as the Hall-effect sensor element only detects vectors perpendicular to it. While this is true in theory and for basic one-dimensional sensors, the development of two- and three-dimensional sensors has expanded the practical applications of magnet-sensor configurations.
Continue reading for more information about 2D and 3D sensors.

Hall-effect sensors are usually specified with a fixed magnet orientation — for example, head-on linear, overhead linear, rotary, etc. — along with a magnet flux value. Most Hall effect transducers have this functionality built in by the manufacturer.

*Magnetic flux is the magnetic field trough a given area.

Switching and Absolute Sensors

The earliest Hall-effect sensors were switching sensors, which activate when the magnetic field strength surpasses a specified threshold value. Switching Hall-effect sensors can function as standalone devices, commonly used in applications like proximity switches, or be integrated with incremental transducers, combining the sensor element and magnet with distinctive characteristics. Typical applications include magnetic encoders and gear tooth sensors.

The basic absolute analog sensor is a radiometric sensor; its output is proportional to the magnetic field strength and orientation. This principle underlies all analog Hall effect sensors, which now come in a wide range of options. Analog sensors are used in linear and rotary transducers that include different characteristics such as output signal, programmable parametric, supply voltage and so on. Analog sensors are used in many applications including linear positioning, steering angle, clutch control, and others.

2D and 3D Sensors

Traditional one-dimension sensors only sense magnetic field perpendicular to the sensor element. This requires precise magnet positioning and motion since the tolerance for air gaps and magnet movement is low. Additionally, material properties such as variations in magnetic flux between magnets and temperature variations must be considered.

With two- or three-dimensional sensors, the magnetic field is measured in two or three dimensions; X, Y, and Z. This is useful for multidimensional positioning, for example in joysticks. It also enables more robust and accurate positioning in rotary and linear transducers by utilizing additional dimensions in the calculation of position.

Explore our rotary sensors with Hall effect.
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