I've been working on a niche type of fluid dispensing machine for a few week and weighing the dispensed fluid was my solution to knowing when to stop. I was concerned that the type of fluid might cause clogs in a standard paddlewheel flow sensor, so I fabricated an external weigh scale using a 2kg load cell and an HX711 breakout and it works very well. The load cell is very sensitive and since I'm using a Raspberry Pi instead of an Arduino, I had to do some specific data processing to deal with timing interruptions.The system works well enough that I'm considering marketing my weight platform as an off the shelf product.
My process actually has very similar problems since it's moving fluids containing biologic materials. That's exactly the reason I chose a weight sensor -- the nasties cause problems with paddlewheel flow sensors! My fluid aspiration is also done by vacuum: to avoid contamination, I pull a vacuum on a sealed container (that is weighed to verify flow) and that vacuum pulls the fluid in through another tube.Using a flow sensor has the issues you mention, although in my case I was mainly concerned with clogs.The point of suggesting weight as a mechanism is that it can be completely decoupled from the fluid path and the sanitary issues don't apply.He could either (a) weigh the final container that the milk is going to be in, or (b) transfer it to an intermediate container that is weighed, then have another pump system to transfer it out.@OP:If the only issue you have with the flowmeter is that air is also being measured, you could add a pressure sensor on the line. That should allow you to see the difference between milk & air and you can ignore the counts when milk is not flowing.
I want to create a flow meter for a milking machine which works on vaccume.I tried hall effecct flow meter senaor, but due to vaccum effect the senaor rotatea even when without milk flow. Alao i doubt that full flow is needed to get the correct results .Can please anyone suggest me a good method??