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CHAPTER 2FLOW METER TYPES & PRINCIPLES
PADDLE WHEEL FLOW METER

Principles and features of paddle wheel flow meters

Various types of flow meters and flow sensors are available. This section summarizes the principles and features of paddle wheel flow meters.

PRINCIPLES

This is classified as a turbine flow meter. Paddle wheel flow meters are generally divided into two mechanical classes as described below:
(1) Tangential-flow paddle wheel flow meters, with a water wheel structure
(2) Axis-flow paddle wheel flow meters, with a windmill structure

The flow and the revolutions of the paddle wheel are proportional to each other. Thus, by spinning the paddle wheel with the force from the flowing fluid, it becomes possible to measure the rate of this flow from the number of revolutions. By embedding a magnet in the rotation axis and on the edge of the paddle, pulses can be extracted as signals, converting the number of revolutions into the flow rate.

FLOW CALCULATION METHODS

Flow per single pulse × amount of pulses ÷ time = instantaneous flow

STRUCTURAL DIAGRAM OF A PADDLE WHEEL FLOW METER

FEATURES OF A PADDLE WHEEL FLOW METER

PROS ・Excellent reproducibility and responsiveness.
・A simple structure with a low price.
・Compact and can perform large-capacity measurement.
CONS ・Extremely sensitive to foreign objects. (Causes clogging)
・Because the paddle wheel spins at high-speeds, periodic maintenance is needed to deal with axial wear or the paddle wheel must be replaced.

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