. Compendium of meteorology. Meteorology. Fig. 3.—Complete radiosonde showing the meteorological modulator, the exposed temperature element, the humidity shield, and the 1680-mc transmitter. in length. These thermistors possess very high negative resistance coefficients, the resistance varying from ap- proximately 20,000 ohms to 2,000,000 ohms for the temperature range of from +GOC to — 90C. In order to decrease errors due to solar radiation, the elements are coated with a suitable lead carbonate pigment which has a reflectivity coefficient of about The coating increases the diameter to
. Compendium of meteorology. Meteorology. Fig. 3.—Complete radiosonde showing the meteorological modulator, the exposed temperature element, the humidity shield, and the 1680-mc transmitter. in length. These thermistors possess very high negative resistance coefficients, the resistance varying from ap- proximately 20,000 ohms to 2,000,000 ohms for the temperature range of from +GOC to — 90C. In order to decrease errors due to solar radiation, the elements are coated with a suitable lead carbonate pigment which has a reflectivity coefficient of about The coating increases the diameter to about in. The experimental results of Brasefield [6] indicate that such elements may be directly exposed to solar radiation without introducing an error in excess of , except at altitudes above 80,000 ft where errors from to may occur. For these altitudes, however, cor- rections can be applied. If such corrections are applied, it is estimated that the probable error of the residual is approximately ± Another important parameter of a temperature ele- ment is its lag constant, defined as the time required for the element to respond to approximately 63 per. Fig. 4.—The selector switch with pressure capsule. of 100,000 ft the lag is about 22 sec proportional to ^ where p is the density. If the temperatures are corrected for lag, then the residual lag error intro- duces a probable error of about ± in the tempera- ture determination. To obtain a reasonable estimate of the over-all prob- able error in determining temperature, it is necessary to consider the following sources of random error: solar radiation (±), residual lag (=), trans- mitter error (±), lock-in error (±), calibra- tion error (±), recorder error (=), and finally, evaluator error (±). From the theory of the prop- agation of errors, it follows that the over-all probable error in temperature measurement is about = Humidity. Unquestionably
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