Hi
This is a follow up to some other posts regarding this sensor, and also to some assistance I was providing.
It was wondered if this sensor could be used to measure the volume of tanks (water not Challenger) and I saw in principle that it should be able to do so with certain caveats.
I had a bit of time in the Evil Lab today and decided to do some empirical tests, nothing
exact just to prove the concept.
I had an 80 Litre dustbin with an internal height of 58cm and diameter of 44.5cm. It should be noted that this is the diameter at the top and the bin tapers down.
In previous tests / posts I found the sensor and Martin's component to be quite accurate to over 2 Metres in a free standing location.
Now this sensor spreads at a 45 degree angle meaning that if in an enclosed space such as my "cyclinder" (dustbin), depending on dimensions of the cylinder, the sound could hit the walls and reflect before reaching the bottom / target. This has the potential to cause misreadings. I also wanted to see what, if any difference putting a lid on top would make.
Calculations suggested that the "beam" would reach a diameter of 44.6cm after travelling 53.72cm, so in theory I should be able to measure this far down into my very high tech cyclinder. Anything further would be a bonus as I couldn't say for certain what would happen after this depth due to reflections from walls.
Modifying my sensor rig to sit as close to the centre of the cylinder as possible It measured 46cm when empty and the same with a lid on top.

- Hi Tech Testing.JPG (87.93 KiB) Viewed 5991 times

- Empty Tank.JPG (90.85 KiB) Viewed 5991 times
This wasn't quite as hoped for as I "should" have been able to reach ~54 before worrying about unwanted reflections. However my High Tech test cyclinder does taper so that would help explain the discrepancy.
I then filled the tank to a depth of 46cm with water. No change in readings were observed as the tank filled and again the lid made no difference.

- Depth ~46cm.JPG (88.32 KiB) Viewed 5991 times
I continued filling the tank to a depth of approx 40cm and the reading then showed 41cm which given the very rough test set up (despite my High Tech cyclinder) was close enough to say it was working.

- Depth = ~40cm.JPG (69.5 KiB) Viewed 5991 times

- Distance = 41cm.JPG (91.54 KiB) Viewed 5991 times
Again the lid made no difference.
Filling the tank further, reducing the depth to ~30cm (from sensor) gave a similar reading as did all further tests. The lid made no difference in any reading.

- Depth = ~30cm.JPG (79.88 KiB) Viewed 5991 times
So, it would seem that you can use this sensor to measure the volume of water in a cylindrical tank, down to the depth (from sensor) where the beam divergence meets the walls of the container.
This was just a very quick and rough test only using the example file, and I hope it is of use.
Regards