HALL EFFECT SENSOR: HALL EFFECT SENSOR Definition of HES: Definition of HES A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field . These are devices whose output signal is the function of magnetic field density around it. Working of HES: Working of HES PowerPoint Presentation: It consist basically of a thin piece of rectangular p-type semiconductor material, passing a continuous current through itself. When the device is placed within a magnetic field, the magnetic flux lines exert a force on the semiconductor material which deflects the charge carriers. As these electrons and holes move side wards a potential difference (Hall Voltage) is produced between the two sides of the semiconductor material by the build-up of these charge carriers. PowerPoint Presentation: Then the movement of electrons through the semiconductor material is affected by the presence of an external magnetic field which is at right angles to it. Generally, Hall Effect sensors are designed to be in the "OFF", (open circuit condition) when there is no magnetic field present. They only turn "ON", (closed circuit condition) when subjected to a magnetic field of sufficient strength and polarity PowerPoint Presentation: The output Voltage or Hall Voltage(VH) is directly proportional to the strength of the magnetic field passing through it. This output voltage can be quite small, only a few micro volts even when subjected to strong magnetic fields. So most commercially available Hall effect devices are manufactured with built-in DC amplifiers, logic switching circuits and voltage regulators to improve the sensors sensitivity, hysteresis and output voltage. Types of HES: Types of HES On the basis of Outputs: Linear Output Hall Effect Sensor. Digital Output Hall Effect Sensor. Bipolar. Unipolar. Linear Output HES : Linear Output HES In linear output Hall effect sensors, as the strength of the magnetic field increases the output signal from the amplifier will also increase until it begins to saturate. Digital Output HES: Digital Output HES When the magnetic flux passing through the Hall sensor exceeds a preset value the output from the device switches quickly between its "OFF" condition to an "ON" condition without any type of contact bounce. 1. Bipolar Hall Effect Sensor: 1. Bipolar Hall Effect Sensor Bipolar sensors require a positive magnetic field (south pole) to operate them and a negative field (north pole) to release them 2. Unipolar Hall Effect Sensor Unipolar sensors require only a single magnetic south pole to both operate and release them as they move in and out of the magnetic field .