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Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
OptiSonde chilled mirror hygrometer
Article Type: Equipment From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 2.
GE Sensing has introduced the OptiSonde humidity indicator, transmitter and data logger, the first chilled mirror hygrometer for industrial applications to claim the precision and repeatability previously found only in laboratory standard instruments. As a result, the new instrument can reportedly be used both to calibrate existing sensors and as a high accuracy, highly stable humidity sensor.
The OptiSonde utilises the technology of choice for monitoring humidity and temperature in laboratories and process environments. This technology has been characterised and documented to produce negligible long-term drift, allowing OptiSonde to act as a transfer standard for humidity, traceable to National Metrology Laboratories. Optisonde can be used to calibrate and verify a wide range of humidity instruments. It is also said to be ideally suited for monitoring and documenting environmental conditions in process and storage areas. Typical applications include monitoring conditions in environmental test chambers, monitoring aerospace engine emissions and heat exchanger and air conditioning performance testing.
OptiSonde's chilled mirror technology involves directly measuring dew point temperature by using an infrared light emitter and detector to regulate heat being removed from a precious metal mirror, regulating a condensed dew or frost layer to a constant mass. The temperature of the mirror is measured by a precision resistance temperature detector. When the mass of the condensed water is at equilibrium, the temperature of the mirror is, by definition, equal to the dew point temperature. By simultaneously measuring the ambient temperature humidity parameters, relative humidity, absolute humidity, volume and mass ratios are calculated by the OptiSonde with high precision.
The new compact and rugged hygrometer is available in bench-top and wall mounted configurations and offers dew point measurement to ^0.28C. For room monitoring, the chilled mirror and temperature sensor is plugged directly onto the chassis, or the sensors can be installed up to 300ft (91m) away and connected via cable. The OptiSonde indicates two user-selected parameters simultaneously as well as system status and diagnostics. In addition to the LCD readout, data are transmitted via two fully scaleable analog signals (4-20mA) and digitally via an RS-232 port. The unit is equipped with a data logger that enables long-term data to be saved. The OptiSonde is supplied with PanaView software to enable data uploading to a PC for graphing and data reduction. The data may also be exported as an ASCII text file format for use in spreadsheets. The OptiSonde also incorporates GE Sensing's patented PACER cycle which is an automatic means of self- cleaning and balancing the sensor optics.
Details available from: GE Sensing, web site: www.ge.com/sensing