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<br />4.2 Total Temperature Sensor <br /> <br />The Rosemount Model 102AUIAF sensor is an hermetically sealed platinum resistance <br />sensing element which provides a measurement of total air temperature. For stability and protection, <br />the sealed element is surrounded by a gold-platinum-alloy radiation shield, which, in turn, is <br />surrounded by a stainless steel shield. Through signal conditioning, the resistance is converted to a <br />linear output voltage, which is proportional to total temperature according to the algorithm in Table <br />2. <br /> <br />Specifications <br />Range: +400 to-600C <br />Time Constant: ~ 1.9:t 0.6 s (speed offlight dependent) <br /> <br />Calibration <br />Calibration in the field is not required. Intercomparison calibrations are performed using an <br />additional temperature probe on the Boulder Atmospheric Observatory (BAO) tower. A <br />calibration was performed on 24 Apri11986. A tower flyby on 13 Aprill990 showed that <br />re-calibration was not necessary. Daily check measurements of temperature and dew point <br />were made with an aspirated pyschrometer. This was used as a basic check that the <br />instruments were in working order, not as a calibration. <br /> <br />o <br /> <br />Operational procedures <br />The instrument was permanently installed, outboard on the right wing, and wired into the <br />aircraft systems. When the scientific power was connected on the aircraft, the sensor and <br />signal conditioner were operational. Connection of the system output to the data acquisition <br />system occurred before the field study. There are no operational considerations. <br /> <br />4.3 Dew Point Hygrometer <br /> <br />A continuous flow of air directed through the General Eastern Model I 0 lIB dew point <br />hygrometer sensing chamber contacts a thermoelectrically cooled mirrored surface. The presence of <br />condensation is sensed optically and electronics maintain the condensate surface in vapor pressure <br />equilibrium with the surrounding gas. When the dew on the mirrored surface is a constant thickness, <br />in equilibrium with the partial pressure of the water vapor in the air sample, the rate of condensate <br />equals the evaporation. At this point, the temperature of the mirror equals the dew point <br />temperature. The conditioned output voltage is proportional to the dew point temperature according <br />to the algorithm in Table 2. <br /> <br />Specifications <br />Range: _750 to +500C nominal <br />Time Response: 10C S-1 typo <br /> <br />10 <br />