Rotary Sensors Hall Effect

The Hall effect is the result of the force acting on electrical charges in motion, known as the Lorenz force. When electrons (negatively charged particles) move at 90 degrees to a magnetic field they experience a force and move in response to that force, creating an electrical current.

Hall Effect

A Hall effect sensor works by measuring the direction and intensity of the current created, or induced, by a magnetic field. This translates into the proximity, direction and velocity of the object producing the magnetic field.

Rotary Motion

One method commonly used to measure rotary motion directly is to rotate a uniform magnetic field around a Hall effect sensor. A sensor placed at the center of rotation experiences the same field, but from different directions.

Angular Position

Strictly, a Hall effect sensor is only responsive to the components of a magnetic field along a single axis, or centerline. However, its response is monotonic -- it changes in one direction only -- over a range of plus or minus 90 degrees of rotation; this enables the sensor to determine its angular position from a look-up table in a microcontroller (a microprocessor on a single integrated circuit).

References

• "Hall Effect Sensors"; Daniel Frei; 2004
• "Hall-effect Sensors: Theory and Applications"; Edward Ramsden; 2006