What Is a Hall Effect Sensor?

A Hall effect sensor is a small device, mounted to a circuit board, which can measure a magnetic field. It is designed around the principles of the Hall effect, in which a magnetic field perpendicular to an electrical current on a circuit produces voltage on the other side. The sensor can be in the form of a single chip, along with components to compensate for temperature changes. An amplifier for the signal is needed to output accurate measurements as well. Analog and digital output Hall effect sensors are available, and both are used in computer, automobile, and industrial control systems.

In an analog Hall effect sensor, the voltage from the output is always directly related to the magnetic field, which can be either positive or negative. Voltage rises with magnetic field intensity, and if no field is turned on then a null voltage represents the value of the power going through. A sensor's output versus input is described by the transfer function which accounts for the output without magnetic fields, sensitivity, and its output range.

With a digital output Hall effect sensor, the output is only defined by on and off states. An analog sensor can be converted to a digital one using a specific circuit, the Schmitt trigger circuit. The states change only when a predetermined level is reached; otherwise the output won’t increase or decrease unless the magnetic field changes significantly enough. Also, digital sensors can be powered by supplies that are either regulated or unregulated, depending on what they are being used for.

A tiny integrated circuit package is all that is needed to house a Hall effect sensor along with its associated electronics. The actual sensors are almost too small to see and can be placed anywhere on a circuit board. At the same time, they can tolerate shock, vibration, and extreme temperature ranges, so Hall effect sensors can be used for speed sensing in industrial control systems. They can also detect the strength and direction of a magnetic field, allowing for direction detection. Use as a position sensor is possible as well.

Electronics with a Hall effect sensor are included in automotive braking and ignition systems. Cell phones and other portable devices have them as well to enhance various functions and applications that require position, movement, and speed sensing. Hall effect sensors also cost less than similar sensors, so electronics can be acquired and developed economically.