How to measure unpressurized irregular water flow
Hi!
I recently hooked up the condensation run off line from my AC to a rain barrel, mostly because the ground on that side of the house wasn't draining the water well. I was then very surprised to find that the 50gal barrel filled up in a little over a week. I've started filling up some watering cans to use in the garden, but this turns into a very manual process and in the long run I would much prefer to tap into the rain barrel for more automated drip irrigation.
Here's my problem: I can gauge when the barrel fills up and it's rough water level, but I have no way to know how much water I have in there at any given point (and quick searches for applicable tools led to ones hundreds of dollars meant for the big water storage tanks). My next thought was to measure how much water is flowing through the pipe via some kind of electronic sensor, but the outflow pipe is not pressurized and does not have a consistent flow of water (variable, and only when the AC runs).
Are there any reliable tools that can help give a digital (and ideally remote) reading for this irregular water flow? Or alternatively a more exact reading of the water in the barrel - at least better than my sharpie scratches on my diy water level?