1/4" Water Flow Sensor Food-Grade Switch Hall Effect Flowmeter Fluid Meter Counter Connect Hosepipe 0.3-6L/min (Pack of 2）

As info, I ordered/received the 2pc Gredia GR-R401 G1/4 Hose Pipe flavor. I got 2 so I could disassemble one and have the other unfettered in case I destroyed the one I was frackin with. I am using this on a water cooled 3d printer hot end, to give Klipper programmatic flow indication. These are 3 full pulses per revolution (6 edges). As another user reviewed, there is a reduction of the ID on the inlet side of the flow meter. I presume this was so that there was a focus of pressure on the rotor blades. It is 1.5mm in diameter (checked with a 1.5mm shaft). At ~35 deg C coolant temp, I am getting ~900-1000 PPM (~333 rpm @ 3 PPR). As the fluid warms, it becomes more viscous and flow increases. I am happy with the product. I opened the orifice on the 2nd unit to 2mm and will test to see if I get comparable usability with the larger orifice, and see if I get overall better flow/performance from the cooling system.

This item claims to be able to flow 6L/minute. I couldn't get more than about 1L/minute through it. I looked into the inlet port, and there's a flow restrictor molded into the port. I measured it's diameter at about 1.3mm. A 1.3mm orifice would flow only 2LPM even with a 200PSI pressure drop, far more than this unit is rated for.