ash73
Posts: 11
Joined: Mon Jan 30, 2017 12:52 pm

super accurate distance measurement with rPi

Wed Jul 04, 2018 12:36 pm

Hi, I need a rangefinder to use with a Raspberry Pi to measure the distance to the surface of a column of water moving up and down in a 15cm diameter 3m long perspex tube, in an indoors environment. The rangefinder would be positioned above the tube. I could either measure the distance to the surface of the water or put a reflective float on top. I need to capture about 5 measurements per second, and ideally I need it to be accurate to +/- a few mm.

From a quick Google the LIDAR-Lite 3 Laser Rangefinder looks to be quite good, but only has a resolution of +/- 1cm.

Also found the Benewake TFMINI Micro LIDAR Module (infrared) and Sharp GP2Y0A02YK0F (infrared), not sure how they compare.

I gather ultrasonic distance sensors are less accurate and too slow for my needs.

Are there any other rangefinders people would recommend?

It doesn't need to be compact, so an off the shelf laser rangefinder would be ok as long as I can somehow hook it up to the Pi.

Thanks!

ash73
Posts: 11
Joined: Mon Jan 30, 2017 12:52 pm

Re: super accurate distance measurement with rPi

Wed Jul 04, 2018 1:20 pm

I've been pointed towards the VL53L1X sensor, for example the RB-Pol-633 board:

https://www.robotshop.com/en/tof-range- ... 53l1x.html

Has anyone managed to hook one of these up to a rPi? Thanks.

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HermannSW
Posts: 1490
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
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Re: super accurate distance measurement with rPi

Wed Jul 04, 2018 2:19 pm

ash73 wrote:
Wed Jul 04, 2018 1:20 pm
Has anyone managed to hook one of these up to a rPi?
Pimoroni has:
https://pypi.org/project/VL53L1X/0.0.1/
⇨https://stamm-wilbrandt.de/en/Raspberry_camera.html

https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://gitlab.freedesktop.org/HermannSW/gst-template
https://github.com/Hermann-SW/fork-raspiraw
https://twitter.com/HermannSW

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Z80 Refugee
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Joined: Sun Feb 09, 2014 1:53 pm

Re: super accurate distance measurement with rPi

Wed Jul 04, 2018 10:43 pm

You could try putting the tube between the two plates of a capacitor and measure the variation in capacitance caused by the amount of conductive fluid there is between them (ie the water).
Military and Automotive Electronics Design Engineer (retired)

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mbrunnig7716
Posts: 1
Joined: Thu Dec 13, 2018 1:46 pm

Re: super accurate distance measurement with rPi

Thu Dec 13, 2018 1:49 pm

I think a draw wire encoder would fit the bill perfectly for you. I'm looking to build my own tensile tester but for more rigid materials so it's not a good fit for me, but for a bow draw should be great.

https://www.amazon.com/CALT-1000mm-Draw ... ent+sensor

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