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Applications of hall-effect rotary-position sensors

Posted: 24 Apr 2014     Print Version  Bookmark and Share

Keywords:Hall-effect  rotary-position  sensors  foot pedal position sensing  HVAC system 

Inside most motorised vehicles, we can find a broad range of components, switches and sensors used for personal transportation or for heavy industry. Designed to measure, monitor and provide feedback, Hall-effect rotary-position sensors can be used in a variety of transport applications such as cars, trucks, buses and boats as well as in a wide range of industrial applications.

Hall-effect rotary-position sensors are designed to measure the angle position of a moving element by utilising a magnetic field instead of mechanical brushes or dials. They use a magnetically biased, Hall-effect integrated circuit (IC) that senses rotary movement of the actuator shaft over a set operating range. Rotation of the actuator shaft changes a magnet's position relative to the IC. The resulting flux density change is then converted to a linear output which can be used to provide feedback to either the operator or vehicle sub-system.

Solid-state Hall-effect technology provides non-contact operation. The internal section of the sensor uses a magnetic field, not a physical brush or wiper that is used in potentiometers. Wipers used in potentiometers can cause friction, which can reduce the products life. Using non-contact magnetic Hall-effect technology in a rotary-position sensor helps reduce worn-out mechanisms, lowers actuation torque and extends the products service life.

The Significant Seven: What Specifications Should Design Engineers Consider when Choosing Hall-effect Rotary Position Sensors?

1. Is durability important? Engineers should consider the type of environment in which the device will be used. For harsh environments, engineers should specify a package that meets IP67 qualifications for enhanced durability. This is especially important for vehicles and machines that are being designed to typically operate in harsh climates and environments.

2. How long is the device specified to operate? Check the products data sheet to determine the products documented cycle life. It may be better to have the sensor manufacturer perform this testing so that your engineering staff does not have to spend time doing this testing work.

3. Should you specify an integral connector? Two important advantages of designing in a sensor with an integral connector are its smaller size and extended life. An integral connected sensor can be smaller than the overall package size of a sensor that relies upon a pigtail connection. This enables developers to design and build smaller overall system packages. Use of an integral connector increases durability because pigtails are notoriously fragile. Wires in a pigtail can become strained, frayed, eaten by rodents or crimped.

4. Is EMI/EMC resistance important for your design? Radio waves of different frequencies can interrupt electronics. Automotive-grade EMI/EMC protection provides reliability in sensor performance against radio frequencies in the environment.

5. Can you utilise a standardised I/O? Using industry-standard AMP termination, 32 mm mounting pitch and universal pin-out styles may help you save time and money. Standard I/Os can greatly simplify drop-in replacement because the mounting points, profile and pin-outs are similar to those of the incumbent device.

6. How flexible do the sensors for your design need to be? Determine if you are working with one power setting or if the sensor should be able to work with a variety of input voltages. It could be beneficial to use position sensors that provide a wide span of operating voltages or ranges. A variety of operating ranges can provide design engineers the resolution needed in the span of travel in many common applications.

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