Hall Effect Sensor
The Hall Effect mentions the voltage or potential difference (Hall voltage) on the other sides of the electrical conductor through which the electric current is flowing, produced by a magnetic field applied perpendicular to the current. Edwin Hall discovered this effect in 1879.
The change in voltage ratio to the product of the amount of current and the magnetic field divided by the element, widths are called the Hall coefficient. This is a property of the material by which this conductor is built-up, as its value depends on the number, type, and properties of the charge carriers that constitute the current.
Hall effect diagram, showing the following:
1.) Electrons (not conventional current)
2.) Hall element, or Hall sensor
4.) Magnetic field
5.) Power source
Working of Hall Sensor
The Hall effect comes due to the nature of the current flow in a conductor. Current contain the movement of many small charges – carrying “particles” (typically, but not always, electrons). The moving charges experience a force, called the Lorentz Force when a magnetic field is present that is not parallel to their motion. When there is not such a magnetic field, the charges follow an almost straight, ‘line of sight’ path. when a perpendicular magnetic field is put on and due to that their path is curved so that moving charges assemble on one face of the material. This leaves equal and opposite charge exposed on the other face, where there is a dearth of mobile charges. The result is an unbalanced distribution of electric charge density over the hall element that is perpendicular to both the ‘line of sight’ path and the applied magnetic field. The charge distribution establishes an electric field that opposes the migration of further charge, so a steady electrical potential builds up for as long as the current is flowing.
Hall Effect in Semiconductors
Whenever a current-carrying semiconductor is put in a magnetic field, the carriers of the semiconductor experience a force in the direction perpendicular to the magnetic field and current field, this is called hall effect in semiconductors.
Application of Hall Effect
The Hall effect sensors are used in many devices and different sensors such as
(i) Fluid flow sensors,
(ii) Current sensors,
(iii) Pressure sensors,
(iv) Displacement measurement,
(v) Magnetic flux measurement.
(i) Fluid Flow Sensors:
The Hall effect sensors can also be used as a position, displacement and proximity sensors if the object is being sensed with a small permanent magnet. Such a sensor can be used to determine the level of fuel in an automobile fuel tank as shown in the figure.
A magnet is fixed with the float and as the level of fuel changes and so the float distance from the Hall sensor changes. The result is Hall voltage output which is a measure of the distance of the float from the sensor and hence the level of the fuel in the tank.
Hall effect devices product a very low signal level and then require amplification “Hall effect sensors” are in fact a device which containing both the sensor and a high gain integrated circuit (IC) amplifier in a single package. Nowadays advances have resulted in the addition of ADC (Analog to Digital) converters and I2C (Inter – integrated circuit communication protocol) IC for direct connection to a microcontroller’s I/O the port being integrated into a single package.
Advantages of Hall Effect
Hall Effect devices when appropriately are immune to
(iii) mud, and
These above properties make Hall effect devices better for position sensing than alternative means such as optical and electromechanical sensing.