i dont use the meters, because all around here we have basically the exact same pressuer at every house that differs with about 2 GPM and about 10 PSI so it really doesnt matter when designing. The Sentry Flow gauges are way better and if you are going to be installing systems quite a bit and need testing then that would be the one to go with.
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers