Help

[jackky]

I used vision system to see my equipment and get the reading from a camera in my computer. how to make the reading can be read easily when my measuring cylinder and the water inside is transparent?

cannot put colouring because my project is measure water density and it will affect its density. Cannot put a float because It will block my limit switch.

Hope to heard suggestions from you guys. Thanks.

 

[JKSH]

Use a black marker to write outside the cylinder?

[jackky]

except this got any others way to do it??

Edited November 16, 2015 by jackky

[ensegre]

dark background, reflection on the interface either from above or below (total internal), perspective reconstruction?

Maybe you can get some ideas from this: Tracing the boundaries of materials in transparent vessels using computer vision

[ShaunR]

1. Change the title of the topic to something descriptive of your question.

2. Shine a coloured light up through the base of the column.

[hooovahh]

1. Change the title of the topic to something descriptive of your question.

2. Shine a coloured light up through the base of the column.

I would suggest both of these things.  Maybe something like a laser pointer shining through it would help detect levels easier.  What is the lighting in the room going to like?  Can it be controlled?  Lighting in vision is basically an art form and not having control over that can make things difficult to impossible.

[drjdpowell]

Are you trying to measure volume?   With a bright light wall behind, the meniscus should be visible.  

 

In this image the level (of a petroleum product) is very clear because of a layer of bubbles (white bubbles, but they appear black against the light wall), but even without bubbles one can pick out the level.

 

[ShaunR]

Maybe something like a laser pointer shining through it would help detect levels easier.

You need a diffuse light source and it helps if you put some black tape on the opposite side so it doesn't get washed out by the ambient light.

If you do it right, the meniscus should be a lot brighter and you will see the tape change from colour (where there is liquid) to black (where there is air)

[ensegre]

You need a diffuse light source and it helps if you put some black tape on the opposite side so it doesn't get washed out by the ambient light.

If you do it right, the meniscus should be a lot brighter and you will see the tape change from colour (where there is liquid) to black (where there is air)

Not the right references IMHO. In the first, light from the bottom reaches the camera at 90° only because the bubbles act as scatterers. Bubbles cause motion and volume uncertainty, though the perpendicular position eases perspective corrections. If the OP cannot even tolerate the density change due to the addition of a small quantity of dye (which, with the image provided, somehow surprises me), I doubt he can put up with bubbles (or possibly other neutrally buoyant seeds). OTOH, I wonder which precision he aims to with his measurements, and whether his aim is achievable with a generic camera even after a careful geometrical image calibration.

 

The second one doesn't even look like a fluid column, but a led matrix display with a "bubbles" animation mode.

 

Not mentioning, shooting in the far IR or UV where water is not transparent... but then he'd need a specialized sensor, and usually they don't came at such high resolutions.

 

I'm taking this homework (?) for the face value stated: (untampered) water -- then density can change with temperature or (extreme) ambient pressure. Or it is not really water but some acqueos solution which has to be left alone. Density - then this water must have been weighted. Must use a camera from an oddball perspective - hence hardly 1% precision in distance measurements. Meniscus curvature effects not mentioned. If volume changes are small, a setup with big reservoir+narrow riser tube may help.

Edited November 16, 2015 by ensegre