Hi

These sensors are really quite neat. I got quite accurate measurements from 4,9 to 44 litres/min, I couldn't go any higher, the output fed into the audio input on the PC with a simple and free frequency meter software. Amazing for a few dollars.

The downturn is the pressure loss across the meter, 0.08 bars at 15 L/min rising to 0,69 bars at 41.8 L/min : Here are what I measured
dP
L/min flowmeter
15 0,08
18,4 0,04
24,7 0,21
26,5 0,24
30,7 0,29
34,2 0,4
37,3 0,51
40,0 0,63
41,8 0,72
42,5 0,69