Hello guys,

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For a professional project, I have to find a distance sensor which can measure distances from 50 mm to 250 mm minimum with a resolution below 1mm like 0.5mm.
I've been looking everywhere and the resolution is never below 1mm for low quality sensors that are often used in arduino projects.
The only ones I found are from OMRON like E3Z LS83-2M which seems to have a great resolution but I can't find a value. The thing is that even if it is called distance sensor, I have doubts for it to just be a proximity sensor.

So do you guys have a reference of a sensor below 200$ that can do it or can you validate my choice of the OMRON sensor pls?

Thank you in advance,
Romain

Try one, and average some number of readings to see if that improves precision. Let us know what you find.

A very rough rule of thumb with sensors is that for each guaranteed factor of 10 improvement in precision, the price goes up by a factor of more than 10.

so 25 centimeter.
interesting.
Does this look good? It's only the sensor and you will have to put together the circuitry to make it wireless (why would you do that)
https://www.mouser.com/datasheet/2/427/vcnlx01-.pdf
and evidently this part is available on mouser. $4 apiace.
Alternatively (I think they are not called proximity sesor?) i found this ultrasonic time-of-flight ranging device. Which is also avaiable on Mouser, but have no details on performance.
https://www.mouser.com/catalog/specsheets/TDK__DS--CH201-v1.1.pdf

After some tinkering, this fellow found that "Using phase, the HC-SR04 can reliably resolve distance changes less than 1 mm." (You won't get that with an out-of-the-box HC-SR04: you have to modify it like he did.)

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https://www.davidpilling.com/wiki/index.php/HCSR04

Even if his findings are true, I'm NOT saying that incredibly cheap sensor is for you. And there are many selection criteria you haven't mentioned.

But I'd be surprised if you can't find a commercial/industrial sensor that can do what you need. For example, these guys have ultrasonic sensors that appear to be in your ballpark, cost-wise and "accuracy"-wise:

BTW, I have found that calling vendors on the and TALKING to a Real Live Person is often the best way to find what I'm looking for. Even if they don't have what I need, they may know a company that does, or can suggest an alternative approach. (And calls usually work much better for this than .)

The key here is that distance changes are being measured, not absolute distance.

As the article points out, measurements of phase changes are limited to one wavelength (8 mm at 40 kHz) total, or about 4 mm of there and back travel. To get absolute distances to that accuracy, you have to accurately count the number of carrier crests to the reflecting object, plus the fraction, which seems difficult to impossible with the HC-SR04. Nice work, though!

You would think that a time-of-flight optical rangefinger thing would exist (ultrasonic is not the most accurate and have a spread), and it should not be terribly expensive, especially if he is willing to put a small reflective surface on the other end.
It's like an industrialized, short-ranged and accurized version of the hand-held measurement thingy that contractors use to take measurements of your house.
For $30 you can measure up to 20 meters with accuracy of within 2mm, along with a screen, battery, software and everything.

I'm amazed you have had so many useful suggestions on such little information. You havent told us ANYTHING about what you are trying to measure the distance TO.
Is it a flat surface? Is it reflective? Is it conductive? Hard or soft? Solid or liquid? Is it moving? What are its dimensions - is it like a wall, a wire, or a bullet?

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