Gate-Type Meters

About measuring with gate-type meters

The gate meter was the earliest device in this class. It consists of a spring-loaded, hinged flap mounted at right angles to the direction of fluid flow in the fluid-carrying pipe. The flap is connected to a pointer outside the pipe. The fluid flow deflects the flap and pointer and the flow rate is indicated by a graduated scale behind the pointer. The major difficulty with such devices is in preventing leaks at the hinge point.

A variation on this principle is the air-vane meter which measures deflection of the flap by a potentiometer inside the pipe. This is commonly used to measure air flow within automotive fuel-injection systems.

Another device in this class is the target meter. This consists of a circular disk-shaped flap in the pipe. Fluid flow rate is inferred from the force exerted on the disk measured by strain gauges bonded to it. This meter is very useful for measuring the flow of dilute slurries but it does not find wide application elsewhere as it has a relatively high cost.

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