CRFS Study Force, Pressure, Flow & Volume

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

Mechanical Gauges Manometers Force summing devices

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

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

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

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

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

Optical Light intensity varies with pressure

Pressure Absolute Gauge Differential

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

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.

Fleisch pneumotach Resistive Linear

Screen pneumotach Resistive Linear

Pitot tube Bernoulli equation

Venturi / Orifice Bernoulli equation

Rotating vane Rotating air stream Low inertia follower Digital counter based

Mass Flow Thermal

Ultrasonic Doppler effect Accurate timing

Differentiation of volume Direct volume measurement Rate of change

Volume Watersealed Rolling seal Bellows Gasometer