TRANSIENT RESPONSE IN RADIO REFRACTOMETERS.
UNIVERSITY OF WESTERN ONTARIO LONDON DEPT OF PHYSICS
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Previous work showed that radio refractometers indicate air refractivity that is too high for relative humidity exceeding 60 percent, for air temperatures above freezing. This error is due to the growth of an adsorbed vapour layer on the sensor whose depth increases to 1.5 micron and refractivity to 1.025 near saturation, where condensation appears. A coating of beeswax reduces the adsorption error substantially. Three aspects of the investigation are continued here, - modification of the h-f test refractometer for reliable functioning at sub-freezing temperatures, development of a technique for measuring its effective thermal lag and temperature coefficient, and extension of the wind tunnel techniques for observations at sub-freezing temperatures. Details of the new test refractometer are given its present thermal lag and temperature coefficient permit it to measure refractivity within 100,000 over height intervals between 1 and 250 cms during a normal balloon ascent. For ventilation rates of 400 and 800 feet per minute, the adsorption effect is the same except at humidities above 90 percent. The adsorption error appears to decrease with decreasing air temperature, above freezing. Preparations are underway for better control of air humidity in the tunnel below freezing point, for improvement in the temperature compensation of the refractometer, and for additional observations on the response of the refractometer to transients in humidity and temperature. Author
- Radio Communications