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- Author or Editor: NORMAN B. FOSTER x
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A simple grating spectrophotometer is used in conjunction with a tungsten filament lamp and projector to measure directly the precipitable water in the atmosphere. Utilization is made of the 1.380 μ water vapor absorption band and the 1.250 μ region for a point of reference. Vacuum thermocouples and high sensitivity galvanometer are employed for energy measurement. Included is a discussion on the calibration and field tests made at the Laboratory of the Institute of the Aeronautical Sciences, Sands Point, Long Island, New York, August and September, 1942. Calibration tests were conducted over optical paths of from 1.5 meters to 52 meters; precipitable water paths were from 0.0023 centimeter to 0.083 centimeter.
A simple grating spectrophotometer is used in conjunction with a tungsten filament lamp and projector to measure directly the precipitable water in the atmosphere. Utilization is made of the 1.380 μ water vapor absorption band and the 1.250 μ region for a point of reference. Vacuum thermocouples and high sensitivity galvanometer are employed for energy measurement. Included is a discussion on the calibration and field tests made at the Laboratory of the Institute of the Aeronautical Sciences, Sands Point, Long Island, New York, August and September, 1942. Calibration tests were conducted over optical paths of from 1.5 meters to 52 meters; precipitable water paths were from 0.0023 centimeter to 0.083 centimeter.
Abstract
A new system developed for calibrating the horizontal incidence pyrheliometer is described. The pyrheliometers to be calibrated are exposed simultaneously with a standard pyrheliometer in an integrating sphere. Calibrations are made by comparing voltages developed by the instruments undergoing calibration with those of the standard pyrheliometer. Calibration of the standard pyrheliometer is based on comparisons with the Smithsonian Institution pyranometer, both out-of-doors on clear days and within the integrating sphere. Advantages of the new system include reproducibility of the calibration within less than one percent. This is due to the reproducibility of the radiation field in the integrating sphere, in which there are relatively small variations in ambient temperature. The calibrations can be done much more rapidly and accurately than was formerly the case when the work was done out-of-doors; clear skies and minimum atmospheric pollution were necessary conditions previously.
Abstract
A new system developed for calibrating the horizontal incidence pyrheliometer is described. The pyrheliometers to be calibrated are exposed simultaneously with a standard pyrheliometer in an integrating sphere. Calibrations are made by comparing voltages developed by the instruments undergoing calibration with those of the standard pyrheliometer. Calibration of the standard pyrheliometer is based on comparisons with the Smithsonian Institution pyranometer, both out-of-doors on clear days and within the integrating sphere. Advantages of the new system include reproducibility of the calibration within less than one percent. This is due to the reproducibility of the radiation field in the integrating sphere, in which there are relatively small variations in ambient temperature. The calibrations can be done much more rapidly and accurately than was formerly the case when the work was done out-of-doors; clear skies and minimum atmospheric pollution were necessary conditions previously.
Abstract
The following devices for simplifying the operation of the Abbot Silver Disk Pyrheliometer are described: (1) an automatic shutter, (2) a simplified heating and cooling timing sequence and (3) an improved method of reading the pyrheliometer thermometer. The authors also describe their experience in automatically recording the silver disk temperature by means of a thermocouple, amplifier, and recorder.
Abstract
The following devices for simplifying the operation of the Abbot Silver Disk Pyrheliometer are described: (1) an automatic shutter, (2) a simplified heating and cooling timing sequence and (3) an improved method of reading the pyrheliometer thermometer. The authors also describe their experience in automatically recording the silver disk temperature by means of a thermocouple, amplifier, and recorder.
Abstract
A recording infrared absorption hygrometer which measures the absolute humidity in a 1-meter light path is described. Record is obtained on a remote self-balancing potentiometer. Use is made of the 1.37 µ water vapor absorption band and a 1.24 µ reference band. Isolation is by means of transmission type interference band-pass light filters. Infrared detection is by means of a lead sulfide photocell and amplifier. Isolation filters are contained on a sector wheel which is rotated to chop an infrared beam. A self-balancing null system is employed whereby the energy in the absorption band is kept equal to the energy in the reference band at all times. Balance is maintained by automatically varying the temperature of the lamp supplying the infrared energy, and the temperature of the lamp is a measure of the water vapor in the sensing path. An index of the lamp temperature is obtained by means of a monitor photocell, and meter or recorder. Included is a discussion on the calibration and field tests made on the instrument at the Weather Bureau Laboratories, Washington, D. C.
Abstract
A recording infrared absorption hygrometer which measures the absolute humidity in a 1-meter light path is described. Record is obtained on a remote self-balancing potentiometer. Use is made of the 1.37 µ water vapor absorption band and a 1.24 µ reference band. Isolation is by means of transmission type interference band-pass light filters. Infrared detection is by means of a lead sulfide photocell and amplifier. Isolation filters are contained on a sector wheel which is rotated to chop an infrared beam. A self-balancing null system is employed whereby the energy in the absorption band is kept equal to the energy in the reference band at all times. Balance is maintained by automatically varying the temperature of the lamp supplying the infrared energy, and the temperature of the lamp is a measure of the water vapor in the sensing path. An index of the lamp temperature is obtained by means of a monitor photocell, and meter or recorder. Included is a discussion on the calibration and field tests made on the instrument at the Weather Bureau Laboratories, Washington, D. C.
