accuracy

I'm running 4 flow sensors. Two 3/4 in (HDRS-FM075) and two 1 inch (HDRS-FM100). In all cases, the measured flow seems about 1/3 to 1/5 of the flow that I'd expect. One 3/4" is connected to a Jebao DCP-10000 - Max 2600GPH This one shows 530 GPH at full power in a short closed loop. It is...