GE Sensing Optica ™ Optica is a General Eastern product. General Eastern has joined other GE high-technology sensing businesses under a new name _ GE Industrial, Sensing. The Next Generation Humidity Reference Standard GE's Optica Series chilled mirror hygrometers offer National Institute of Standards and Technologies (NIST) _ traceable humidity, temperature and pressure measurements for the connected generation. Now data is accessible from anywhere, any time, from within a browser over the Internet or from your intranet. • Temperature • Relative humidity (% RH) • Dew/frost point (Td) • Absolute humidity (m/v) • Mass mixing ratio (m/m) • Volume mixing ratio (v/v) Optica Measures • Wet bulb (Tw) • Enthalpy (h) • Water vapor pressure (e) • Pressure • Alarm relays • Analog outputs Fundamental dew point measurement is a primary measurement used as a transfer standard for calibrating other humidity instruments and sensors. Chilled mirrors are also the sensors of choice when process and laboratory measurements call for high precision without long term drift. Optica may be used with five, fully interchangeable chilled mirror sensors to provide a measurement range from -112°F to 185°F (-80°C to 85°C) dew point with 0.36°F (0.2°C) or better accuracy. Inputs for a 100 S RTD and silicon-based piezoresistive pressure transducer ensure precision measurements, which are used to convert the dew point to any metric, English or user-defined unit of humidity measure. g
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The Next Generation Humidity1/4 color VGA enables up to six parameters to be displayed or 4 x 40 dot matrix enables three parameters to be displayed Operating Temperature 32°F to
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GESensing
Optica™
Optica is a General Eastern product. General Eastern has joinedother GE high-technology sensingbusinesses under a new name_GE Industrial, Sensing.
The Next Generation HumidityReference Standard
GE's Optica Series chilled mirror hygrometers offerNational Institute of Standards and Technologies (NIST)_traceable humidity, temperature and pressuremeasurements for the connected generation. Now datais accessible from anywhere, any time, from within abrowser over the Internet or from your intranet.
• Temperature
• Relative humidity (% RH)
• Dew/frost point (Td)
• Absolute humidity (m/v)
• Mass mixing ratio (m/m)
• Volume mixing ratio (v/v)
Optica Measures
• Wet bulb (Tw)
• Enthalpy (h)
• Water vapor pressure (e)
• Pressure
• Alarm relays
• Analog outputs
Fundamental dew point measurement is a primarymeasurement used as a transfer standard for calibratingother humidity instruments and sensors. Chilled mirrorsare also the sensors of choice when process andlaboratory measurements call for high precision withoutlong term drift. Optica may be used with five, fullyinterchangeable chilled mirror sensors to provide ameasurement range from -112°F to 185°F (-80°C to 85°C)dew point with 0.36°F (0.2°C) or better accuracy. Inputsfor a 100 S RTD and silicon-based piezoresistive pressuretransducer ensure precision measurements, which areused to convert the dew point to any metric, English oruser-defined unit of humidity measure.
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Communications
• Ethernet port
• Java-based applet loads in web browsers
• Data logger 6 megabyte memory
• Recorded data uploads in ASCII format
• Exports to spreadsheets
• Real time "strip chart" graphing
• Color VGA or 4 x 40 matrix display
Software
The Optica software is easy to navigate. Users selectreadout display, strip chart, analog output scale, digitalcommunications, self-diagnostics, cleaning and datalogging with intuitive pull-down menus. Setup values canbe saved in memory and loaded anytime, either locally orfrom anywhere via the Ethernet port.
In the Lab or on the Plant Floor
• Calibration labs
• Process control
• Clean rooms
• Environmental test chambers
• Precision HVAC monitoring and control
• Fuel cells
• Heat exchanger and refrigerant coil calorimeters
• Thermal processing/heat treating
• Semiconductor manufacturing
• Storage areas
• Pharmaceutical validation chambers
• Engine test cells and emissions testing
• Aircraft engines and turbines
Functionality
The Optica simultaneously measures dew point,temperature and pressure. The analyzer is equipped withprogrammable math functions to produce custom units.In, exp +, -, x and / functions enable derived engineeringunits to be displayed, recorded and transmitted to dataacquisition systems. The analyzer input channel is astandard 4 to 20 mA/0 to 5 VDC input, so the Optica canbe connected to any type of process transmitter and beconfigured to display engineering units.
Chilled Mirror Sensors Theory ofOperation
GE’s chilled mirror hygrometers are used in standardsand metrology labs as well as in industrial applicationswhere precise and repeatable humidity measurementand control is required. The inherent accuracy and longterm stability provides many advantages over othertypes of humidity measurement technologies. Chilledmirrors fundamentally measure the dew or frost pointtemperature directly by controlling a reflective surface toan equilibrium temperature between dew/frostformation and evaporation, and precisely measuring thetemperature of the mirror at this point.
“Plug and play” setup is easily accomplished withstandard connectors for power, sensor and analog outputs.
GESensing
GE's chilled mirrors consist of a small polished hexagonalrhodium, or platinum mirror attached to thermoelectriccooling module (TEC). The Optica analyzer's servocontroller applies current to the TEC, which causes themirror to cool. The mirror is illuminated with a regulatedGas emitter, which transmits light in the infraredspectrum. The light reflected by the mirror is received bya photodetector. When water vapor condenses on themirror as water or frost (ice crystals), the light receivedby the photodetector is reduced due to scattering. Thisresults in the servo controller reducing the powercausing the mirror to slightly warm. The Optica's controlsystem will modulate the amount of current flowingthough the TEC to maintain a temperature where therate of condensation and evaporation of watermolecules and the mass of water on the mirror isconstant. The resulting temperature of the mirror is then,fundamentally by definition, equal to the dew or frostpoint temperature. A precision four-wire platinum RTDimbedded in the mirror measures the temperature. Theaccuracy of the dew point measurement has beenvalidated to an accuracy of ±0.36°F (±0.2°C) dew/frostpoint. The precision can also be enhanced to ±0.27°F(±0.15°C) dew/frost point.
Dry bulb temperature is measured with a precise four-wire 100 S platinum RTD and pressure is measuredwith a piezoresistive silicon pressure transducer. Thedew/frost point and dry bulb RTD resistance signals areconditioned and amplified by the Optica monitor todisplay and transmit dew/frost point and temperature.The pressure sensor transmits an amplified 4 to 20 mAsignal that is powered by the Optica. The cardinalmeasurements of dew/frost point, dry bulb temperatureand pressure are used to calculate other humidityparameters such as relative humidity, wet bulb, massmixing ratio, volumetric mixing ratio, absolute humidity,enthalpy and water vapor pressure values usingpsychometric equations.
The RTD sensor is imbedded in the chilled mirror andnever comes in contact with the process or testenvironment. The wetted parts consist of the platinum orrhodium mirror, a stainless steel or mylar vapor barrierand epoxy sealant. The net result is drift-free humiditymeasurement designed to maintain accuracyspecifications for many years.
Chilled mirrors require a nominal flow rate across themirror to achieve the optimal dew/frost formation andresponse time. The sensor should either be installed in aduct with moving air or be equipped with a samplingpump. The optimum flow rate is 0.5 to 5 SCFH (0.25 to 2.5 L/min). GE provides sampling systems to temperature
condition, regulate the pressure and filter process airprior to reaching the chilled mirror. Our applicationengineers will discuss your application in detail andprovide a recommendation for the system best suited toyour needs.
Self Cleaning and Digital Control
LED regulation Thermoelectricheat pump control
OPAMP
Light emitting diodesPhoto detectors
Thermoelectriccooling module
Rhodium orplatinum mirror
Precision four-wire PRTD
Power
Optical balance
Gas flow
For environments where physical contaminants such asdust, oil mist and pollen are present, the use of asampling system with a filter media is recommended.The filter media must be hydrophobic so as to notabsorb or release water vapor into the test stream. Overtime the mirror can be etched or pitted by particulate,altering the light scattering characteristics. GE mirrorsare field replaceable. The standard rhodium mirror maybe upgraded to platinum for industrial applications.
GE developed a patented contamination compensationscheme called PACER® (Program Automatic ErrorReduction). The PACER cycle may be initiated manually orby programming a timed cycle. The cycle starts bycapturing the data (during the PACER cycle a constantvalue is transmitted) and cooling the mirror well belowthe dew point such that a thick dew layer forms on themirror. The mirror is then rapidly heated. During theheating a significant amount of soluble and some non-soluble contamination is flash evaporated. Thecontamination left on the mirror tends to aggregate indry islands or spots (much like a glass that comes out ofa dishwasher). This process leaves approximately 85% ofthe mirror clean. The light signal received by thephotodetector is compared against a referenceLED/photodetector and the two signals are "balanced,"effectively negating the effect of the residualcontamination left on the mirror. The PACER cycle worksvery well, but eventually manual cleaning may berequired. All of GE's chilled mirrors are accessible for
Optical system automatically adjustsfor correct reflectance(5 seconds)
Prevailingdew point
Cooling
Heating
Endof cycle
Startof cycle
Typical PACER cycle
Slew rate
Dewpoint
Oscillation
Time
Tem
pera
ture
Analog control
Time
Tem
pera
ture
Digiloop control
Slew rate
Dewpoint
0.05°C temperature steps
manual cleaning. Cleaning is a simple process consistingof wiping the mirror with a cotton swab wetted withcleaning solution or distilled water. (Distilled water isrecommended as the final cleaning agent.)
GE developed Digiloop™ control to overcome thelimitations of traditional analog PID (Proportional Integraland Derivative) control. Analog temperature controlproduces oscillations particularly at high or tracehumidity levels. It is difficult to apply self-tuning or PIDconstants to analog control loops, which are overdamped or under damped. Digiloop utilizes digitalsampling and feed-forward control by taking time-basedsamples when the dew point is within a predeterminedproportional band. By recording the oscillations, thedigital control effectively predicts the magnitude ofchange and adjusts the current to the thermoelectriccooling module, which steps the mirror temperature in0.09°F (0.05°C) increments. This results in a significantlyimproved control and dew point precision.
GESensing
Models• Color VGA with data logger and Ethernet
communications available in bench, rack or wall mount styles
• 4 x 40 dot matrix available in bench, rack or wall mount styles
Power95 to 265 VAC, 50/60 Hz, 200 watts
Electrical I/OIEC-style AC receptacle (bench mount), screw terminalblock (wall mount), multipin chilled mirror andtemperature sensor/cable connectors, screw terminalsfor analog outputs, DB-9 for RS232 and 10 base-T forEthernet*
Measured ParametersDew point, temperature and 4 to 20 mA/0 to 5 VDC
Calculated ParametersRelative humidity, wet bulb, mass mixing ratio, volumetricmixing ratio, absolute humidity, water vapor pressureand enthalpy in English and metric units, as well as user-configured units
Inputs1/3 Class A DIN 43760, 100 S RTD and dew/frost pointand dry bulb temperature. Loop powered 4 to 20 mA DCat 500 S maximum load
AccuracySystem accuracy ±0.36°F (±0.2°C) for dew/frost point,±0.27°F (±0.15°C) for temperature, 0.5% full scale (FS) forpressure
RangeGoverned by sensor
HystersisNegligible
Sensitivity0.1% FS
A/D16 bit
OpticaSpecifications
Data Logger Memory6 megabytes*
Display1/4 color VGA enables up to six parameters to bedisplayed or 4 x 40 dot matrix enables three parametersto be displayed
Vapor BarrierMylar (upgradeable to stainless steel)
Inlet/Outlet1/4 in OD tubing compression fittings
Electrical ConnectorMS-style multipin connector mates with 2120 cable
Weight4 lb (1.8 kg) net
Accessories
P Platinum mirror
X Enhanced accuracy ±0.27°F (±0.15°C) Td
S Stainless steel vapor barrier
5 in(127 mm)
3.6 in(91.44 m
m)5.7 in
(144.78 mm
)
3.1 in(78.74 mm)
1/4 in(6.35 mm)
compressionfitting
GESensing
Sensing ElementFour-wire 1/3 Class A DIN 43760 RPT, 100 S @ 32°F (0°C)
Dew/Frost Point AccuracyStandard: ±0.36°F (±0.2°C)Optional: ±0.27°F (±0.15°C)
Sensitivity>0.05°F (>0.03°C)
Repeatability±0.09°F (±0.05°C)
HysteresisNegligible
Cooling StagesTwo-stage TEC module
Auxiliary CoolingNot applicable
Depression153°F (85°C) at 167°F (75°C) body temperature andatmospheric pressure
Typical Measurement Range14°F to 167°F (-10°C to 75°C) dew/frost point (Td) in air @167°F (75°C) body temperature in 77°F (25°C) ambienttemperature and atmospheric pressure. Equivalent to 0.7% to 100% RH.
Other parameters based on calculations.
Sample Flow0.5 to 5.0 SCFH (0.25 to 2.5 L/min)
Operating Temperature5°F to 212°F (-15°C to 100°C)
Vapor BarrierMylar (upgradeable to stainless steel)
Inlet/Outlet1/4 in (6 mm) OD tubing compression fittings
Electrical ConnectorMS-style multipin connector matesIEC receptacle for AC power
Weight34 lb (16 kg) net
Accessories
P Platinum mirror
X Enhanced accuracy ±0.27°F (±0.15°C) Td
S Stainless steel vapor barrier
8.77 in(223 mm)
1.8 in(46 mm)
7.17 in(182 mm)Ø 0.31 in
(7.9 mm)4 places
16.3 in(414 mm)
GESensing
Sensing ElementFour-wire 1/3 Class A DIN 43760 RPT, 100 S @ 32°F (0°C)
Dew/Frost Point AccuracyStandard: ±0.27°F (±0.15°C)
Sensitivity>0.05°F (>0.03°C)
Repeatability±0.09°F (±0.05°C)
HysteresisNegligible
Cooling StagesFive-stage TEC module
Auxiliary CoolingLiquid cooling jacket
Depression, Liquid Cooled202°F (112°C) with 59°F (15°C) cooling water
Typical Measurement Range-112°F to 59°F (-80°C to 15°C) dew/frost point (Td) in air@ 77°F (25°C) and atmospheric pressure with 59°F (15°C)cooling water.
9 S/P/P standard accuracy, platinum mirror,stainless steel vapor barrier (D2)
Ordering CodeGuide
Temperature Sensor
Sensor0 No temperature sensorA T-100 with 10 ft (3 m) cable (standard accuracy)B T-100 with 10 ft (3 m) cable (enhanced accuracy)X T-100 with build to fit cable (standard accuracy)Z T-100 with 10 ft (3 m) cable (enhanced accuracy)
Pressure Sensors0 No pressure sensorA PT-30A 10 ft (3 m) cable (standard)B PT-30A build-to-fit cableX PT-300A 10 ft (3 m) cable (standard)Z PT-300A build-to-fit cable
All specifications are subject to change for product improvement without notice.Optica™ is a trademark of GE. GE® is a registered trademark of General Electric Co.Other company or product names mentioned in this document may be trademarks orregistered trademarks of their respective companies, which are not affiliated with GE.g www.gesensing.com