I don't know why you make calculations in the print. Because the rpm counts up, every time the magnets come by, the rpm gets one higher. At the end of the loop the rpmHV should be reset to zero, to make it work
And I also need the other 2 RPM and FLOW parameters, because I also make calculations with them. (fuelusage now, fuelusage tank, fuelusage trip, overall fuel usage)
Why do you write: #define INTERVAL 500UL what is the difference with int interval=500; ? (no offense I want to learn)
But to go short I have still interference with the flowmeter. But only with the "new" hall sensor.