I have one of these FlowVis meters that was just installed with our new pool in Jan 2014, since we also have a variable speed pump, it has been very interesting to have. My Ecostar VS is rated for 80gpm with my 2" plumbing and running it at full speed was generating about 28 psi at my filter, and about 100 gpm at the meter, so it was very useful to know I needed to turn down the pump. So I used it to help set the 4 speeds that the Hayward ProLogic uses:
s1 - 1035 rpm - 30 gpm - 0 psi : min speed required to get the flow switch in the UV system to come on
s2 - 1725 rpm - 53 gpm - 6 psi : min speed required to get both the heaters flow switch enabled
s2 - 2415 rpm - 65 gpm - 11 psi : just a speed I chose because it was the same rpm difference from s1-s2 to s2-s3 (690 rpm)
s2 - 3105 rpm - 92 gpm - 22 psi: next speed up using 690 rpm, and speed I intend to use for vacuuming
knowing what I know now, I would not have needed the meter, I did determine s1 & s2 without the use of the meter, but it was interesting to know
I believe my salt cell is activated at speeds even lower than s1, I use s1 or s2 for routine daily filtering, and I could have experimented with the vacuum to see what speeds it works best at, the Polaris cleaner has not been installed yet but trial and error with it is probably going to determine what I use for s3
I am an engineer by training so I love my meter, and even though I now realize it is mostly a luxury, I am still glad I got it.
Mike