Measuring and testing – Gas analysis – Moisture content or vapor pressure
Patent
1988-07-05
1989-10-31
Chapman, John
Measuring and testing
Gas analysis
Moisture content or vapor pressure
73597, 374119, G01W 102, G01N 2902
Patent
active
048768898
ABSTRACT:
The water vapor content for air in drier ducts, ovens, furnaces and the like is determined by a measurement of sound speed which is done by measuring the time difference between sound pulses reflected by two reflectors spaced a known distance apart in a guide tube. The transmitter-receiver is located at one end of the tube. The tube has enough number of holes to allow the hot moist air to get into the probe tube. A non-porous tube containing dry air placed in the same duct provides a similar measurement of dry-sound speed. The ratio of the two speeds of sound or the two measured time intervals is a simple function of the water vapor content practically independent of temperature thereby providing a very accurate measurement of water vapor content over an extremely wide range of temperatures. The sensor is accurate, immune to harsh environments, has an extremely low time constant, has absolutely no hysteresis and needs no calibration.
REFERENCES:
patent: 4083765 (1978-04-01), Lawson
patent: 4255964 (1981-03-01), Morison
Lawson et al., Humidity Measurements by Polymer Electrolytic Hygrometer for Harsh Environments, Sensor Expo 1987, pp. 49-59.
Rotronic Instruments Corp., Humidity-Temperature Transmitter.
Pacer Systems, Inc., "Vaporsense 1000".
Honeywell Brochure, Capacitive Solid State Dew Point Hygrometer.
Vaisala Inc., Econ 200--The New Industrial Dew Point Measuring System.
Venkateshan et al., "Acoustic Temp Profile Measurement Technique for Large Combustion Chambers", ASME Paper 87-WA/HT-14, Submitted as Disclosure 07/108813 on 10/15/87, Found Allowable on 05/16/88.
Kwack Eug Y.
Shakkottai Parthasarathy
Venkate-Shan Shakkottai P.
Chapman John
Roskos Joseph W.
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