
When you browsed you local marina chandlers store, you have seen these meters in their simplest form. They are made to protrude through the hull of a boat and indicate how many knots it is going!Normally these flow meters are an injection molded / moulded cross shape for the paddle, with a small magnet encapsulated inside the end of one of the four paddle blades. The paddle is usually installed in an injection-molded housing. The housing has a sensor or proximity switch sealed in glass, set in to the housing. When the paddle blade passes the sensor, a signal is sent to some form of counter or display. The rate of signals is calibrated to a flow rate.
The light weight of the paddle, is the cause of it to having very little momentum. Therefor, instantly the flow varies, the paddle's speed of rotation changes. The smallest of pressure shocks can accelerate the paddle.
It is generally necessary to stabilize flow and to intercept shocks when deploying these low cost meters. When paddle meters are used with diaphragm type dosing pumps, an advisable damper size is 50 times the volume of one pump diaphragm displacement. This will convert erratic jerking of the paddle into constant rotation.
UNDERSTANDING FLOW OR PRESSURE PULSATION
WAYS TO GO
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