I was trying to find a way to measure the amount of air that's flowed by a specific point. I am assuming there is a fairly simple way to measure this but I can't find it.
What I'm trying to accomplish is essentially a lung capacity tester that I can see the amount increasing on the fly. It doesn't need to be measuring exact lung capacity but relative capacity between several different people.
I hope I gave enough info to be helpful but let me know if there is anything else that would be important and I'll respond back quickly.
Any ideas/suggestions/recommendations would be greatly appreciated.
These are not cheap to buy, but it should be straight forward to make one. Basically you need a rotating vane in a tube and some way of measuring the number of rotations. Like an opto sensor or a hall effect sensor.
The trick is to get the balance right between the resistance the rotating element gives and the amount of coupling it has.
If it is too tight then you send the vane whizzing along and the momentum it has will give you extra turns and a false reading after the breath is finished. If it is too lose then it won't pick up enough breath to make an accurate reading.
You might like to google hot-wire anemometer. This type of device measures flow by determing the change in current (heat) in a thin copper wire imposed into the air stream. This eliminates the concern about flow restriction by a vane in the stream and has the neatness of no moving parts.
Wow. thanks for the quick response guys. That sensor is exactly what I was looking for. But I may try building one myself because that just sounds like a fun project
Another idea would be a potentiometer connected to a spring-loaded vane inside an enclosed space (a check valve for example), the more air that pushes on the vane, the further it moves, and thus the more it turns the potentiometer.
