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Topic: Ultrasonic sensor interference with walls (Read 303 times) previous topic - next topic

LiborVojtek

Hi all.

I would like to ask, if I should be worried about interference from the walls when I will use ultrasonic sensor inside closed metal (relatively) small tubular container.
(To measure height of stuff inside.)

Alternatively, is there any better contactless way I can use?

Thanks,
Libor

wvmarle

Depends on the actual geometry of your setup.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

jremington

Quote
if I should be worried about interference from the walls
Yes. Easy to test.

Slumpert

The ultrasonic is going to "hear" the first reflection back to it.

A ribbed culvert will bounce the signal right back, while a smooth wall tube will might carry the sound far, far away.

LiborVojtek

Depends on the actual geometry of your setup.
You can imagine it as a smooth metal bottle with approximately 10cm diameter and 30 cm height, with the sensor on top.

Yes. Easy to test.
Of course, but I do not have the components, yet. And I wanted to get some advise, before ordering them.

The ultrasonic is going to "hear" the first reflection back to it.

A ribbed culvert will bounce the signal right back, while a smooth wall tube will might carry the sound far, far away.
I am not so familiar with inner working of these modules. So maybe the better question is, if the bounce of waves will be strong enough to trigger the sensor.

wvmarle

The cone of the sensor is about 30 degrees. That means it WILL hit the walls before getting out, and the point where the tube gets too narrow for the cone may very well be the point that gives you reflections.

Why placing it in such a tube in the first place?
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

LiborVojtek

Why placing it in such a tube in the first place?
That is the container I have/need/want to work with.

However, if it helps, I can use some other type of contactless distance sensor, like light based.
But I suspect, that if the content will be granular, it could reflect the beam away from the sensor and also if the content will be fluid it could let the beam through.

wvmarle

Depends on the material used and the wavelength of the light. Light sounds like a better solution as you for sure won't have problems with the walls.
Usually IR is used, that will indeed shine through water but be reflected by opaque liquids like milk. Powers will generally be no problem, they reflect in all directions so also back to the sensor.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

LiborVojtek

Depends on the material used and the wavelength of the light. Light sounds like a better solution as you for sure won't have problems with the walls.
Usually IR is used, that will indeed shine through water but be reflected by opaque liquids like milk. Powers will generally be no problem, they reflect in all directions so also back to the sensor.
Well, I might have ran myself into a dead end, as what I have in mind is a universal container, which can eventually contain anything (water, milk, flour, gummy bears, sand, gravel, molten iron, ... :-D ).

wvmarle

Water will require thorough waterproofing.
Molten iron requires heat proofing.
Ultrasound doesn't work well with soft materials (absorbing the sound - clothed people are often missed by ultrasound distance sensors); IR won't work with materials that are either transparent to it (water) or emit a lot of IR themselves (molten iron).
So no, your total universal wish won't work. You have to narrow it down.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

LiborVojtek

#10
Aug 20, 2019, 12:47 pm Last Edit: Aug 20, 2019, 12:49 pm by LiborVojtek
You have to narrow it down.
So let's start with plain old water.

What would be the best contactless option to measure volume of water in smooth metal cylindrical container with 10 cm diameter and 30 cm height?

I found some post somewhere saying that they managed to do this with IR, but then later admitting, that it is not 100% reliable.
But I assume, that there should be some option.
Surely I am not the first/only one who wants to do something like this, or am I?

wvmarle

Ultrasound works wel with water, a nice and smooth surface.

If your tube is too narrow: try ir bouncing off a float.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

LiborVojtek

try ir bouncing off a float.
Float would violate "contactlessness" of the solution.


So the conclusion is basically to try and see what would work.
Maybe some ultrasound sensor with smaller sound wave cone, or light sensor with different wavelength.


Thank You all for the replays.

wvmarle

The cone of the sound is determined by physics, not much you can do about that. Same for light.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

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