The whole business of turning on the electric fuel pump to bring in cooler fuel to mitigate vapor lock now seems like pretty weak tea. Leave the pump on for 15 minutes and you get 1 Qt of liquid flow.
That is about what I show on my Dynon. I have always wondered if and how this is taken into account when the Dynon is showing fuel flow. If I am showing 5 GPH is that really 4 GHP for flight planning purposes?
There's only one fuel flow sensor, and it measures the fuel flow out of the tank. The return flow is not measured. The difference is "calibrated out" by adjusting the sensor calibration so that the fuel totalizer winds up with the right amount at typical cruise power and fuel flow.
I'm not sure why Van's took the "single sensor and calibrate it out" approach - it seems a little janky to me (the return line is additive but the calibration is multiplicative).
On the other hand, I suppose an extra sensor would be extra cost, build time, wiring, and another potential point of failure. In any case it seems to work well enough.
My fan looks like this. Works great! Love it!