Hall Effect Sensor | Working , Advantages , Application
HALL EFFECT SENSOR
Hall Effect sensor is a type of magnetic sensor. A Hall Effect sensor is a transducer that varies its output voltage in response to change in magnetic field. In 1879 Edwin Hall discovered that: “when a conductor or semiconductor with current flowing in one direction was introduced perpendicular to a magnetic field a voltage which could be measured at right angles to the current path”. The voltage is.directly proportional to the number of flux lines passing through the conductor, angle at which they pass through it and amount of current used. When a current-carrying conductor is placed into a magnetic field, a voltage will be generated perpendicular to both the current and the field. This principle is known as Hall Effect.
Figure 1.37 illustrates the basic principle of the Hall Effect. It shows a thin sheet of semiconducting material (Hall element ) through which a current is passed.
The output connections are perpendicular to the direction of current. When no magnetic field is present shown in Figure 1.37(a), the current distribution is uniform and no potential difference is seen across the output.
When a perpendicular magnetic field is present shown in Figure 1.37(b), a force is exerted on the current. This force disturbs the current distribution in resulting potential difference (voltage) across the output.
The Hall effect sensor can also be used to measure the fuel level in a fuel tank (Figure 1.39). The float has buoyancy in the fuel. It floats up as the fuel becomes more. The gap between magnet and hall sensor will changed. It results the changing of the output. The springs allow the float to move only vertically.
Applications of hall effect sensor
- Hall sensors are used for proximity switching, positioning, speed detection and current sensing applications
- Hall sensors are commonly used to time the speed of wheels and shafts such as for internal combustion engine ignition timing or tachometers.
- They are used in brushless DC electric motors to detect the position of the permanent magnet
- Typical applications are the detection of a moving part replacing a mechanical limit switch. Another common use is in indexing of rotational or transnational motion
Advantages of hall effect sensor
- It is relative low cost compared to electromagnetic switches
- High frequency operation is possible
- It is used for multiple purpose usage as displacement, position and proximity sensors
- It is solid and robust and capable of working in severe environmental conditions as they are immune to humidity contamination
- There is no contact bounce problem
Sensor becomes weak during offset effects caused by misalignment of contact in Hall element and piezo-resistive effects
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