I would like to measure some fluids with the help of the Arduino.
I´ve got a mini pump to pump the fluid from the initial container to its destination container at a more or less exact rate.
My first idea was to switch the pump on for 1min and measure the amount of fluid it pumped and calculate the normalized value (1ml) of this to put in the exact amount and therefore get the amount that is needed each time when the pump runs for time x.
The problem is that I never know how much fluid is still left in the tube (ignore air bubbles for now). Thats why I need some kind of sensor when the fluid is passing a certain point in the tube (best place would be near the front where the fluid exists the tube).
The sensor should not be in the tube since Im transporting chemicals that could destroy the sensor in the long run.
Does a simple LDR and LED sensor should do the trick even when the fluid is pretty clear? Or are there any other ideas?
asuryan:
Does a simple LDR and LED sensor should do the trick even when the fluid is pretty clear? Or are there any other ideas?
Using light sounds like a promising approach but It depends on the fluid really.
If the fluid is very clear, you might be able to detect refraction, or a reflection from the underside of the meniscus if you get the LED and sensor arranged suitably. Also if the meniscus is reflecting, that would cast a shadow somewhere that you could probably detect.
I tested a little bit here. The fluid is not 100% clear and even with clear water there is a difference in the LDR reading. Without anything in the tube I get a reading of approx. 120 and with water in the tube I get 160. The difference is not that big but it could be enough.
I'd think that dosing of specific amounts of fluids is achieved by valves, with separate inlets for each component. The tubes never should become empty, because the exchange of remaining fluid by air, entering from the outlet, can not normally be controlled. Once the desired amount of fluid has been pumped out, the valve is closed or closes itself (nonreturn valve), preventing further liquid dropping out of the tube.
Details depend on the type of pump you're using. Rotary pumps can be stopped at almost every angle, others only after every dose step.
