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Unformatted text preview: 11-111-1FlowMeasures of Fluid FlowFlow velocity.Speed of material flowing past a plane.Volumetric flow.Volume of material passing a plane per unit time.Mass flow.Mass of material passing a plane per unit time.When fluid incompressible. . .. . .flow velocity, volumetric, and mass flow are proportional.Types of Flowing Fluids to be MeasuredLiquid in closed conduit. (E.g., water in a pipe.)Liquid in an open conduit. (E.g., water in a canal.)Gas in an closed conduit.Slurry (solids suspended in liquids) in a closed conduit.Different transducers may be required for each situation.11-1EE 4770 Lecture Transparency. Formatted8:20,24 February 1999 from lsli11.11-111-211-2Some Major Types of SensorsRotation.Fluid forces an object placed in flow to rotate. Speed of rotationis measured.Obstruction.Fluid flow is partially obstructed. Pressure is measured on bothsides of obstruction, flow rate deduced.Heat dissipation.A heating element is placed in the flow. Flow rate deduced byamount of heat removed.Head.Measure fluid level flowing into a drop.11-2EE 4770 Lecture Transparency. Formatted8:20,24 February 1999 from lsli11.11-211-311-3Rotation SensorsForce of flow causes some object to rotate. Two types will be dis-cussed, turbine and paddle wheel.Turbine TypeUsed to measure volumetric flow in a closed conduit.FlowMagnetic Reluctance TransducerPlastic Pipe SectionTurbineTypical Construction.Turbine placed in flow in a plastic section of pipe.Turbine blades made of metal.Magnetic reluctance transducers placed outside pipe near blades.Flow causes turbine to spin.Rate of spin measured by magnetic reluctance sensor.11-3EE 4770 Lecture Transparency. Formatted8:20,24 February 1999 from lsli11.11-311-411-4Model FunctionThis includes the turbine, the magnetic reluctance sensor, a conditioningcircuit, and a frequency counter.Ht1(x) =k x, wherekis a constant called thek factor, having units ofone over volume.Paddle WheelUsed to measure volumetric flow in an open conduit.Consists of a wheel partially immersed in the flow.Flow causes wheel to turn.Same model function as turbine flow meter.11-4EE 4770 Lecture Transparency. Formatted8:20,24 February 1999 from lsli11.11-411-511-5Paddle Wheel/Speed Measurement ExampleDesign a system to convert process variablex[0,80mls], flow in apipe, into a floating-point numberH(x)to be written into variablepaddleFlow, whereH(x) =xsml. The value must have a precisionof.1mls. Use an FP-2502 paddle-wheel flow sensor.Solution OverviewFlowSensor+-V-CounterResetClockRegisterData InData OutClockData OutBuffer andInterfacer = readInterface();ClockFlow sensor generates a voltage pulse train.Digital comparator converts to logic level....
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This note was uploaded on 12/11/2011 for the course EE 4770 taught by Professor Staff during the Fall '99 term at LSU.
- Fall '99