Black: Clock, outputs write signal every second (you can change the update rate by increasing both decider combinators values by the same amount)
Red+Green: Memory cells. Green stores the value from red before red reads the current values (slightly modified design by XKnight, I'm using the arithmetic+constant combinator to cancel out the write signal)
Yellow: Negate the values from the green memory cell, add 0 to the values from the red, combine at the pole. You can do this at the arithmetic combinators directly. I just decided to do it like this so i can use the stored values for something else too (don't know what yet)
The rate/s are all signals on red at the medium electric pole at the bottom. The values to measure go in from the right (the barely visible tank in the image)
You can track multiple items/liquids just by feeding them all in at the right memory cell.
If the input and output rate of the tank/chests are the same it will output 0, since it isn't really measuring throughput. But it's good enough i think.
Any improvements/combinator savings are welcome, since I've only put together some parts found on the forums
Same as above, only compacted. Clock signal runs on green on the pole, flow rate on red.
Blueprint strings (without the Nixie tubes)