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Volumetric measurement of liquid in transparent container

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JS:
Usually specs are the other way around, so you have a few less significant digits of uncertainty. That being precision being smaller than accuaracy.

JS

jaredwolff:
I've used capacitive in the past. Spaced out the pads per units of volume so I knew, approximately, how many mL were removed. Capacitive though becomes a pain when any other elements are involved (like your hands!) (This was, by the way, using a flexible PCB not something completely at the bottom of the cup)

I'd also suggest (if it hasn't been already), especially if you're working from the bottom, using ultrasonic. If you have a homogeneous mixture (water or water like) ultrasonic works like a charm.

Jared

Berni:
Since you are aiming for pretty low resolution of 100ml on a 3 liter container it would make sense to glue a flex PCB with capacitive pads on the side of the container. One could then use a MCU with plenty pins to measure the capacitance on 30 such pads and determine at what pad the capacitance suddenly jumps up. Additional sloped pads between the existing pads could be used to narrow i down the resolution further if needed.

But usually the easy way of sensing level in a open tank is to simply screw a pressure sensor into the bottom (Provided you know the density of the liquid will always be the same)

tpowell1830:
Some clothes washing machines have an open tube that goes to the bottom of the washing tank so that when you rotate the load size switch to different positions, the machine can sense how much water is in the tank. I have not examined one of these circuits or setups very closely, but there would be varying air pressure in the tube as the water rises, so I am assuming it has a pressure sensor at the top of the tube. Makes sense...

Hope this helps...

DTJ:

--- Quote from: tpowell1830 on June 26, 2018, 11:30:02 pm ---Some clothes washing machines have an open tube that goes to the bottom of the washing tank so that when you rotate the load size switch to different positions, the machine can sense how much water is in the tank. I have not examined one of these circuits or setups very closely, but there would be varying air pressure in the tube as the water rises, so I am assuming it has a pressure sensor at the top of the tube. Makes sense...

Hope this helps...

--- End quote ---

I've seen industrial washing machines use this arrangement with an MPX style pressure sensor.

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