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Mechanical Components - Flow Rate Sensors

Flow Rate

Flow Sensoroad Cell
Flow Rate Sensor
Venturi Valves

A Venturi valve reduces the cross section of a pipe to create a pressure differential from the normal pipe diameter. The pressure differential increases with the velocity of the flow to aid in determining the flow rate.

Transit-Time Flow Measurement Principle

A transit-time flowmeter measures the effect of a liquid's flow velocity on bi-directional acoustical signals. An upstream transducer (T1) sends a signal to a downstream transducer (T2) that in turn sends a signal back. When there is no flow, the time to go from the T1 to T2 is the same as the time going from T2 to T1. However, when there is flow, the effect of the liquid's flow velocity on the acoustical signal is to assist the signal in the up to downstream direction and hinder the signal in the down to upstream direction. This creates the time difference by which the liquid's flow velocity, and ultimately the flowrate, is determined.

Pitot Tubes

Pitot tubes have been used in flow measurement for years. Conventional pitot tubes sense velocity pressure at only one point in the flowing stream. Therefore, a series of measurements must be taken across the stream to obtain a meaningful average flow rate.

Flow Transducers

Fluid flowing through the sensor spins a magnetic rotor to induce a voltage in a coil. An electronic circuit measures the frequency of the electrical pulses generated and computes the flow rate. This rate is converted to a 0-5 VDC or 0-20 MA output proportional to the flow rate and also used to control a relay. The relay trip point may be preset at the factory or adjusted by the user by turning a potentiometer.





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