Positive Displacement meters offer the convenience of being accurate in any orientation. There are 2 different types of positive displacement meters offered by Flows.com: Nutating disc and Piston.
Nutating disc meters are commonly used as residential water meters. They look very similar to a multi-jet meter on the outside, but the internals are completely different. The popular Neptune T10 is of this type, but it does not offer a pulse output option.
Piston type positive displacement meters are yet another completely different internal design. They are great for low flow rates. Pulse output is available on both series of this type. 1 pulse per gallon or 20 pulses per gallon.