Hall Effect Sensors
We use Hall Effect sensors every day and most people don’t know what they are or how we use them. Hall Effect sensors work as indicators in most devices, it uses a group of sensors to relay information. A magnetic field and position is measured and the sensor will convert the magnetic signal into codes or data. Magnetic sensors are designed to respond to negative and positive magnetic fields within an application. Electricity and magnetism combined make things move and also let you know when they don’t, such as a low fuel indicator, low ink on a printer, key card devices and digital temperature readings.
Hall Effect sensors are used in an analogue or digital capacity. Analogue or linear sensors produce a continuous voltage output which increases when a strong magnetic field is present and decreases when a weak magnetic field is present. Digital or output sensors uses a Schmitt Trigger with preset hysteresis connected to an amplifier. The output from the device will switch to an on or off position, this is determined by preset values. When the magnetic change exceeds the preset values, the Hall sensor will respond accordingly. Digital sensors only have two states which are off and on. There are two forms of digital output sensors, bi-polar and uni-polar. Bi-polar sens Hall Effect sensors ors need a positive magnetic field or south pole to function and a negative field or north pole to release it. A uni-polar sensor uses a magnetic south pole to function and release it as it moves in and out of the magnetic field.
Most devices using Hall Effect sensors are operated by a single magnet attached to a moving shaft which is then activated by the magnetic field. There are several different types of magnetic movement such as head-on, sideways and positional which are used to detect movement. Regardless of the configuration being used, the magnetic lines of flux are positioned perpendicular to the sensor on the device and the correct polarity must be used. This will produce better results by creating the maximum amount of sensitivity.
The two most common applications using a single magnet are head-on detection and sideways detection.
Head on detection creates an output signal; in linear devices this indicates the strength of the magnet. The magnetic field is perpendicular to the Hall Effect sensors, it moves forward or towards the sensors. The distance of the magnetic field in relation to the sensor, in this case closer will create a higher output voltage.
Sideways detection can be positioned vertically or horizontally and passes through a fixed line of center such as air gap distance to count rotations of moving parts. The magnetic field will move side to side across the face of the Hall Effect sensors. The position of the magnetic field will determine the linear output voltage which can be positive or negative.
This is another form of head-on detection, when there is absence of magnetic energy the device will be in the OFF state. When positive magnetic energy is moved towards the active area of the Hall Effect sensor the device will be in the ON state.
When buying Hall Effect sensors, get them from an electronics specialist with a reputation for quality. Gopher Electronics is an industrial franchised distributor of electric mechanical components and a company you can trust. With over 60 different manufacturers products you know you can get the right parts for your needs.