@@ -16,11 +16,12 @@ It is based on a discrete electrostatics solver (shown below), and also document
## Magnetic
Another position measurement uses the magnetic field instead of the electric field. Among magnetic field sensing technologies, hall effect sensors are the most ubiquitous. Integrated circuits with arrays of hall effect sensors are available at extremely low cost in very dense packages. Using differential pairs of these elements, non-contact rotary and linear encoders can be made. A great resource for designing such magnetic devices is the <ahref='https://sensing.honeywell.com/hallbook.pdf'>Honeywell Hall Effect Handbook</a>. Austrian Microsystems makes a variety of these devices for sensing position or rotation of a magnet.
Another position measurement uses the magnetic field instead of the electric field. Among magnetic field sensing technologies, Hall effect sensors are the most ubiquitous. Integrated circuits with arrays of hall effect sensors are available at extremely low cost in very dense packages. Using differential pairs of these elements, non-contact rotary and linear encoders can be made. A great resource for designing such magnetic devices is the <ahref='https://sensing.honeywell.com/hallbook.pdf'>Honeywell Hall Effect Handbook</a>. Austrian Microsystems makes a variety of these devices for sensing position or rotation of a magnet.
For more sensitive, low field devices magnetoresistive sensing elements are often used. <ahref='http://www.physics.nyu.edu/kentlab/Lectures/Pappas_Tutorial_APSMM2008.pdf'>David Pappas of NIST compares</a> noise floors of these technologies, noting Hall effect sensors register around 300,000 $`pT/\sqrt{Hz}`$, while magnetoresistive show roughly 200 $`pT/\sqrt{Hz}`$. Honeywell sells a variety of very sensitive magnetoresistive magnetometers, and NVE Corporation sells sensors based on giant magnetoresistance for very low field measurement. Despite these favorable properties, sensors with these technologies are usually more expensive and less dense than those using the Hall effect.
For more sensitive, low field devices magnetoresistive sensing elements are often used. David Pappas of NIST compares noise floors of these technologies, noting hall effect sensors register around 300,000 ```pT/\sqrt{Hz}```, while magnetoresistive 200
Integrated circuits are available with extremely sensitive magnetoresistive and hall effect sensors.
