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<br />Calibration <br />A standard calibration was performed on the instrument in March 1992. System balance <br />checks were performed during the project to assure correctness of the instrument. Daily <br />measurements of temperature and dew point were made with an aspirated pyschrometer. This <br />was used as a basic check that the instruments were in working order, not as a calibration. <br /> <br />Operational procedures <br />The dew point hygrometer system, with sensor permanently mounted on the aircraft fuselage, <br />was powered and allowed a warm-up/stabilization of at least 30 minutes prior to an <br />operational ground check via the aspirated psychrometer. After the take off, often while <br />enroute to the research area, the dew point system was placed in the balance mode, allowing <br />the control circuitry to be electrically compensated for the optical effects of accumulated <br />contamination on the optical surfaces. The functi.on switch was then returned to dew point <br />mode for sensing and data collection. <br /> <br />4.4 Static Pressure Transducer <br /> <br />The Rosemount Model 1201F2A14A1A Pressure Transducer consists of a precision <br />capacitance pressure-sensing capsule with electronic signal conditioning. It senses the ambient air <br />pressure through a static pressure port mounted on the skin of the aircraft cabin. Conversion from <br />pounds per square inch absolute (psia) to millibars is through the algorithm given in Table 2. <br /> <br />Specifications <br />Range: 0 to 15 psia <br />Static Error: :t 0.10% FSP max. <br />Resolution: Continuous <br /> <br />Calibration <br />None is required in the field. An audit of the instrument performance was conducted during <br />the BAO tower flyby 13 April 1990; no adjustment was necessary. A calibration with <br />reference to a dead weight piston gauge was performed June 1992. A check of the transducer <br />is made before each flight using an aneroid barometer which. has a National Institute of <br />Standards and Technology (NIST) traceable calibration. <br /> <br />Operational procedures <br />The instrument, tubing and static port were permanently mounted on the aircraft fuselage and <br />wired into the aircraft system. When the scientific power was enabled in the aircraft, the <br />instrument was powered. The instrument output voltage was connected to the data <br />acquisition system before the field study. There is no additional operation required. <br /> <br />4.5 Solar Radiation Sensor <br /> <br />The LI-COR Model LI-200SB Pyranometer Sensor, uses a silicon photodiode for measuring <br />solar radiation received from the whole sky (1800 field of view). Often referred to as global solar <br /> <br />11 <br />