A Hall Effect sensor is a type of sensor which detects the presence and magnitude of a magnetic field using the Hall Effect. The output voltage of a hall sensor is directly proportional to the strength of the field.
Hall sensor is mostly used for proximity sensing, positioning, speed detecting, and current sensing application. Thus a hall sensor is combined with threshold detection to act as a binary switch which is commonly seen in industrial application such as the pneumatic cylinder also they are used in consumer equipment. For example, some computer printers use them to detect missing papers and open covers.
Thus Hall Effect sensors are device which are activated by an external magnetic field. We know that a magnetic field has two important characteristics i.e. flux density, and polarity. When the magnetic flux density around the device or sensor exceeds a certain pre-set threshold, the sensors detect it and generate the output voltage called the Hall Voltage.
Hall Effect Sensor Principle
It is basically consist of a thin piece of rectangular p-type semiconductor material such as gallium arsenide (GaAs), indium antimonite (InSb) or indium arsenide (InAs) passing continuous current through itself. So when the device is kept within the magnetic field, the magnetic flux line exerted the force on the semiconductor material; which deflects the charge carriers, electrons and holes, to either side of the semiconductor slab. This will result of the magnetic force they experience passing through the semiconductor material. Thus because if this potential difference is produced between the two side of the semiconductor material to build up of these charge carrier. This movement of electron in semiconductor is affected by the presence of the external magnetic field which is at the right angles to it and this effect is greater in a flat rectangular shaped material.
Thus the effect of generating a measurable voltage by using a magnetic field is called the Hall Effect. Hall Effect sensors are available with either linear or digital output and the output signal for linear sensor is taken directly from the output of the operational amplifier with the output voltage being directly proportional to the magnetic field passing through the Hall sensor.
Hall Effect Sensor types
There are two types of sensors devices with linear (or analogue), output and those have digital output.
Analogous sensor has a continuous voltage output that increases with the increase in magnetic field and decreases when in a weaker magnetic field. With linear output Hall Effect sensors, as the strength of the external field increases as the device come into contact with magnetic field, the output signal increase in parallel until it reaches the limits imposed by the power supply.
The digital output device has a Schmitt trigger which is a bi-stable circuit that steadily increases and decreases the output when the voltage rises and falls to different thresholds. So when the magnetic flux passing from the hall effect sensor it exceed the device’s preset value which make the device switches it from OFF and ON and the sensor moves in and out of the magnetic field. The build in hysteresis in the device eliminates any oscillation of the output signals.
Digital Hall Effect sensor type
There are two type of the digital Hall Effect sensor
- Bipolar
- Unipolar