The 9th International Symposium on Physical Measurements and
On-Line Physical Measurements
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Transcript of On-Line Physical Measurements
Making Physical Measurements
On-Line Physical MeasurementsTerry A. RingDepartment of Chemical EngineeringUniversity of UtahTypes of InstrumentsFlow MeasurementLevel MeasurementTemperature MeasurementPressure MeasurementDensity MeasurementConcentrationAnalytical InstrumentationChemical SensorsSafety, Weight and Misc.On-Line ConnectionsAnalogue SignalmV, mA, Volts, Amp, Watts, otherAmplification to Industrial Std Scales4 to 20 mA+ 5 to -5 VDigitizationStep size = Scale/(2^N)N = bits in a byte of A-to-D boardCalculation Precision 8, 10, 12 16 digits or 32 digits of binary words are common
Flow MeasurementOrifice platesPitot tubesRotary FlowmetersMass Flowmeters Coriolis, ThermalMagnetic FlowmetersSight Flow Indicators paddleVariable-area Flowmeters rotametersVenturi TubesV-cone FlowmeterMany, many others
Sight Flow MeterRotametersTurbine Flow Meter
Thermal Mass Flow Meter
Orifice Plate / Venturi Meter
Level MeasurementFloat Level DevicesLevel GaugesDifferential Pressure Level DetectorsSlip tubes and DipsticksUltrasonic Level DetectorsLaser Level DetectorsLoad Cells on TanksMany, many othersTemperature MeasurementFilled-bulb, Glass-stem thermometerThermocouplesThermistorsResistance Temperature Detectors (RTDs)- platinum resistance thermometer PyrometersFiber-Optic ThermometersOthersThermocouples
Thermocouple
Fermi Dirac Distribution=Fermi Level or 50% fill level =Chemical Potential of electron
V=I*RRTDsBased on the electrical resistance of a conductor increasing with temperatureMost accurate, reproducible and stable thermal element availableRelatively expensiveVery preciseFragile but can be industrially hardened
ThermistorsSemiconductors made from mixtures of pure oxides (Mn, Ni, Cu, Zn, Fe, etc.) sintered at > 1800 oFVery good for narrow span measurementOutput highly non-linear, not good for wide span applications, fragile unless industrially hardenedSmall size, fast responseLack of stability at higher temperaturesPressure Measurement Bourdon pressure sensors- C Bourdon- Spiral Bourdon- Helical BourdonDifferential pressure instrumentsElectronic pressure sensors- strain gauge transducers- piezoelectric sensorManometersDiaphragm sensorsPressure MeasurementAbsoluteGaugeVacuum
Piezoelectric SensorPressure SensorLiquid Density MeasurementHydrometersWeighing a fixed volumeOscillating Coriolis DensitometersHydrostatic DensitometersRadiation Densitometers liquid/sludgeVibrating Densitometers Liq/sludge/gasHydrostatic DensitometersProcess Piping=P/(g h)25Radiation Densitometerh
Radiation or LightX-raysBeers LawI/Io= exp(-kcL)
Chemical SensorsGas AnalysisElectrochemical AnalysisCO sensoralcohol sensorIon mobility
Drift Cell Analysistime the ions spend in the drift cell td can be obtained in terms of P/V.L = length of cellV= Voltagevd = drift velocityKo= mobilityP, T = Pressure and Temperature, subscript o is on-line conditions, without subscript is inside instrument (typically vacuum)
Create Ions by Plasma
Mobility depends on MW and ChargeOn-Line Analytical InstrumentsInfra RedGas ChromatographyLiquid ChromatographyUltra VioletVisibleMass Spectrometer Mw 1 to 60 or 1 to 300.
How would each of these work?Time delaysSpectroscopy
Liquid / Gas Chromatography
Mass Spectroscopy
Mw=106.12 gm/moleCapillaryVacProcessSafety, Weight and Misc.Relief ValvesRupture DiscsLeak Detectors -Anemometers air and gas flowsBoroscopes inspect remote or limited-access locations reactors, process lines, etc. (fiberscopes)Weighing Electronic Load CellsOn-Line ConnectionsAnalogue SignalmV, mA, Volts, Amp, Watts, otherAmplification to Industrial Std Scales4 to 20 mA+ 5 to -5 VDigitizationStep size = Scale/(2^N)N = bits in a byte of A-to-D boardCalculation Precision 8, 10, 12 16 digits or 32 digits of binary words are common
Keep it Running Well KNOW YOUR EQUIPMENTAccuracy and PrecisionUNDERSTAND THE LIMITATIONS OF YOUR EQUIPMENT CALIBRATE AS MUCH AS IS REASONABLE Maintain Equipment so it will Perform Reliably