I am reviewing laser measurement techniques at nanometer resolution.  I need to go beyond that, but wanted to be sure I have a good foundation.  This article is helpful:

"A review of nanometer resolution position sensors: Operation and performance"
Andrew J. Fleming at

https://pdfs.semanticscholar.org/a4e5/72ca05d17881c875767f6fd848a222365390.pdf

It includes many low cost methods, and encourages the use of statistical measures that cannot be gamed or spun for marketing purposes.  My interest is on the "interferometer" and "encoder" categories, since the sensors need to be insensitive to magnet fields. When he wrote this in 2013, the sampling rate was in the kilosamples per second (ksps) range.  Now the same methods can use Msps and Gsps low cost solutions.

[ "capacitive positions sensors" "nanometer" ] and [ non contact "atomic force" "nanometer" ] yield many useful efforts, but much reported is heavy on potential markets and dreams, then practical low cost commodity sensors you and I can use.

I definitely need to look more at piezo devices and linear motors.  If my pendulum starts to swing I need to get out of the way, then track closer and closer as it settles down.

A LOT of these things are the end result of people pushing older amplifier and ADC technologies, and they are about a thousand times more expensive than the new ones. But I cannot ignore anything.  I wish there were a way to help all the older instrument makers to upgrade.  There are still a lot of older instruments that do not use embedded processors, data sharing, modeling or statistics at all.

This one at http://www.lionprecision.com/capacitive-sensors/ seems well reasoned and helpful, but one glance at the photos, and I know it is well beyond my meager budget.  They do mention "Simple capacitive sensors, such as those used in inexpensive proximity switches or elevator touch switches, are simple devices and in their most basic form could be designed in a high school electronics class. ", so I am going to be reading "Capacitive Sensor Operation and Optimization (How Capacitive Sensors Work and How to Use Them Effectively)" at http://www.lionprecision.com/tech-library/technotes/cap-0020-sensor-theory.html to learn from a master craftsman.

Go to run.  I am reading so much my sight keeps going out. Wish I had some help.