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Published byDante Stelling Modified about 1 year ago

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CRFS Study Force, Pressure, Flow & Volume

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Force & Pressure Mechanical Strain Gauge Piezo-resistive Capacitive Inductive Optical

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Mechanical Gauges Manometers Force summing devices

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Strain Gauge Wire or foil which thins when stretched Resistance increases when stretched Usually used in pairs or groups of 4

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Wheatstone Bridge Circuit Diaphragm flex stretches some & compresses others Increases sensitivity & linearity Full or half bridge

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Piezo-resistive Semiconductor chip Resistance changes when flexed May include amplifiers

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Capacitive Capacitance between diaphagm & 1 or 2 fixed plates Requires AC Limited by characteristics of gap contents

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Inductive Inductance changes produced by metal diaphragm on 2 fixed coils Requires AC

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Optical Light intensity varies with pressure

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Pressure Absolute Gauge Differential

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Flow Fleisch pneumotach Screen pneumotach Pitot tube Venturi / Orifice Rotating vane Mass Flow Ultrasonic Differentiation of volume

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Reynold’s Number v s - mean fluid velocity, L - characteristic length (equal to diameter 2r if a cross- section is circular), μ - (absolute) dynamic fluid viscosity, ν - kinematic fluid viscosity: ν = μ / ρ, ρ - fluid density.

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Fleisch pneumotach Resistive Linear

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Screen pneumotach Resistive Linear

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Pitot tube Bernoulli equation

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Venturi / Orifice Bernoulli equation

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Rotating vane Rotating air stream Low inertia follower Digital counter based

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Mass Flow Thermal

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Ultrasonic Doppler effect Accurate timing

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Differentiation of volume Direct volume measurement Rate of change

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Volume Watersealed Rolling seal Bellows Gasometer

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