Measuring minute rotation or distance

[Bern1937]

Looking for ideas on how to measure the distance between two pieces of material, an inch or so square. If I have a solid rod 100 inches long hanging down from a pivot, what are some ideas to measure any swing action? I am thinking about movement on the bottom end of the rod as small as possible. Cannot have any physical contact with anything, other than the support and pivot point. Have experimented with a flag and laser light beam, but just not satisfied yet with the results. Thinking about maybe a stationary plate and another plate on the swing, and measuring the capacitance ( as part of an oscillator) between them. Then I can measure the frequency. The amount of movement around 0.1 inch and less. Spacing would be in the same area of measurement. I’m just at head scratching time for some more ideas. This system would be mounted in a box with temp. control and control for air movements. This is all very vague and iffy, I know, because this is for a crazy idea and experiment I am thinking about and working on. Tnx for any thoughts.

 

[Bluejets]

As in most instances, a photo or a drawing of your intended mechanical setup is worth in clarity,many thousands of words.
What immediately springs to mind when you mention rotational, is a shaft/rotor encoder.
Many available and relatively cheap these days, possibly $30 or less.

 

[Alec_t]

Capacitive sensing sounds good. An alternative might be an optical arrangement which produces and senses Moiré fringes.