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Sub-mm precision ultrasonic or inductive distance sensor for use with Raspberry Pi?

Hi there,

I am trying to keep my hardware/ coding skills alive and spruce up my bicycle wheel truing stand. I need to figure out the required hardware + software for the following:

I want to build a non-contact distance measurement sensor system and get the output "into" my computer for display in a graphical user interface. I know I could omit the latter step with going directly onto a mini-LCD screen, but trying to use this a learn-another-programming-language learning experience (I've coded Matlab galore, pondering Python for this project).

General system components:
Sensor - [something - RasPi or Arduino I guess] - laptop (running debian) - GUI displaying continuous sensor reading

Sensor:
I've web-searched the hell out of this, but not finding anything quite answering my questions. I want to continuously measure the distance from the sensor to a bicycle wheel rim braking surface. Material is aluminium, shiny, though not smooth. Biggest problem with the web-search is being swamped by proximity sensor results (on/off) rather than a distance proportional output signal and much lower resolution projects. I rule out IR or optical sensing, now stuck between ultrasonic and inductive sensing, though tending to the latter for a faster response/adjustment to change time.

Sensor criteria (other than reasonable $$):
- total sensing range: ca.5mm
- sensing accuracy 10 to 100micron/ 0.01 to 0.1mm - don't ask if that's needed, a bit of overkill, I know, but a bit of OCD doesn't do any harm, eh?
- fast-ish sampling rate (so that when I turn the wheel, the number on the screen updates nice and fast, guess >25Hz is sufficient).

[Something - RasPi or Arduino]:
I know that I could omit the laptop GUI part (mini-LCD, LED array, etc), but keen to learn/ practice a little Python with this project, so I guess I am tending to the RasPi, but I am open minded. All I want is the analogue sensor out to end up as a digital reading "inside" my computer to be passed to my GUI as a reading. Essentially a mini A2D converter. Not fussed whether the output is in actual distance units or in arbitrary units/ current units (I guess the sensors put out a proportional current signal?).

GUI:
Depending on the above, how do I best get the signal "into" a Python program? A moderate fast sample rate >25Hz should suffice.

Any help with this would be greatly appreciated!

Gave you some links in the tech section.

Non-contact will be very tricky. Why bother ?