Hall Effect Sensor

ME207 – Advanced Mechatronics ISteven Li10-19-2009

Background• Magnetic field sensor based

on Hall Effect• Hall Effect Discovered in

1879 by Edwin Hall• Applications:

▫ Current sensor▫ Analog multiplication▫ Position/Motion sensing▫ Spacecraft propulsion (HET)

Edwin Hall, 1855-1938

Operating Principles

• Lorentz force:

• Accumulation of charge on conductor produces Hall Voltage:

• In semiconductors (InAs):

(source: http://en.wikipedia.org/wiki/File:Hall_effect.png)

1. Electrons 2. Hall element, or Hall sensor3. Magnets4. Magnetic field5. Power source

Implementation

• Common digital Hall Effect Sensor IC package▫ Current source, Hall Element, Differential Amplifier, Schmitt Trigger

• Magnet/HES arrangements▫ Example: window/tab vs. magnet wheel

• Quadrature arrangement packages allow for direction sensing

(source: http://www.sparkfun.com/datasheets/Sensors/Magneto/ATS177.pdf)

Tradeoffs & Applications• Advantage over optical/contact encoders as position sensor• Voltage isolation as current sensor• Must be used in couple with magnets

• Position/Rotation sensing• Tachometer• Gear tooth sensor• Anti-lock brake systems/traction control systems• HDD precision servo• Ignition firing timing• Extreme environment H/I (JS, keyboard, etc)

• Power sensing (analog multiplication)• Hall Effect Thruster