A Hall effect sensor is a type of transducer that measures the presence and strength of a magnetic field. It is based on the Hall effect, which is the generation of a voltage difference across an electrical conductor when it is placed in a magnetic field perpendicular to the current flow. The Hall effect was discovered by Edwin Hall in 1879.
The working principle of a Hall effect sensor can be explained in the following steps:
Basic Structure: A Hall effect sensor typically consists of a thin strip or a flat piece of semiconductor material, often made of gallium arsenide or indium arsenide, with four terminals - two for the supply voltage (Vcc and GND), one for the output (Vout), and one for the input current (I).
Applying Current: When a current (I) is passed through the Hall sensor, it generates a flow of charge carriers (electrons or holes) within the semiconductor material.
Magnetic Field Interaction: When a magnetic field is applied perpendicular to the direction of the current flow (magnetic field lines are at a 90-degree angle to the current path), it exerts a force on the moving charge carriers. This force causes the charge carriers to be deflected to one side of the semiconductor material.
Charge Separation: Due to this deflection, an imbalance of charge carriers occurs on the opposite sides of the Hall sensor. One side becomes positively charged, and the other side becomes negatively charged, creating an electric potential across the sensor.
Hall Voltage: The voltage that appears across the sensor due to this charge separation is called the Hall voltage (VH). It is directly proportional to the strength of the magnetic field, the current passing through the sensor, and the geometry of the Hall sensor.
Output Signal: The Hall voltage is measured at the output terminal (Vout) of the sensor. The output voltage can be amplified and conditioned as necessary for further processing or control purposes.
Polarity: The polarity of the Hall voltage depends on the orientation of the magnetic field with respect to the direction of the current. If the magnetic field is in one direction, the Hall voltage is positive, and if it's in the opposite direction, the Hall voltage is negative.
Applications of Hall effect sensors include:
Proximity sensing (detecting the presence or absence of a magnetic field)
Current sensing (measuring current in electronic circuits)
Position and speed sensing in rotating devices (e.g., automotive wheel speed sensors)
Contactless switches and latches
Hall effect sensors are widely used in various industries due to their non-contact nature, reliability, and ability to function in harsh environments.