User manual VAISALA MITRAS BROCHURE

[. . . ] MITRAS provides many operational and reliability benefits: · Conformance to all ICAO and WMO requirements for RVR and Meteorological Optical Range (MOR) · Fully automatic operation with excellent accuracy and stability · Unique contamination detection and compensation · Double baseline for CAT IIIB by means of two different beams from one transmitter · Extensive built-in monitoring to verify performance and to generate warnings before failures actually occur · Verified operation in all weather conditions SYSTEM STRUCTURE The standard MITRAS Transmissometer consists of a light transmitter and a light receiver installed at a suitable distance from each other. MITRAS measures transmission of white light over the baseline path and converts the measurement value to the corresponding MOR value. The transmittance measurement resolution of MITRAS is better than 0. 1 % and the measurement accuracy is better than 1 %. A single baseline MITRAS can be easily and economically upgraded to a double baseline system when extended measurement range is needed for CAT IIIB applications. The two baselines are realized by adding an individual lens system in the transmitter unit and a second receiver unit. [. . . ] 10 000 m (Double baseline is required in CAT IIIB operating category. ) One background luminance meter, mounted on top of the light transmitter, is sufficient per runway to measure the background luminance value needed in visibility calculation. window contamination exceeds an acceptable level, a warning is sent out and the window can be cleaned. This unique function extends the cleaning intervals significantly, while the user is assured of consistently high data quality. Each MITRAS unit continuously monitors several technical parameters and generates warning and alarm messages in cases of fault. The MITRAS status can be monitored remotely over the modem line. Automatic monitoring in the transmitter and receiver covers supply voltages, internal temperatures, optical performance including correct calibration/alignment and detected failures. This information can be interrogated by the service technician before leaving for the site. Warnings of lamp ageing and window contamination are generated as needed. The xenon flash lamp's nominal lifetime is 8 years at one flash per second. MITRAS extends the lifetime by adjusting the flash rate depending on visibility. An interval of one second between flashes is used in low visibility. The flash interval increases stepwise to 10 seconds when visibility improves to a measured value above 10 km. SUPERIOR ACCURACY In the WMO intercomparison of visibility measurements, MITRAS achieved the best results concerning measurement accuracy. MITRAS measures both the transmitted and the received light pulse amplitudes. Instead of re- lying on estimates of projected light power, every transmitted pulse is measured. Atmospheric transmittance is then calculated as the ratio of received and transmitted light power on a single pulse basis. Receiver electronics are gated to receive only light pulses from the transmitter, and will not accept any interference light during the interval. The wide-bandwidth white light of the transmitter's xenon flash lamp and the photopically corrected receiver sensitivity provide an ideal match of the human eye's spectral range. Interference from other light sources, such as the sun or the aircraft lights is minimized by accurate beam forming. Light distribution across the beam is even. Multiple forward scattering and dispersion in fog is minimized. [. . . ] 160 kW Lamp life 55 000 hours Spectral output range 300 . . . . 1100 nm Microprocessor 8031 with application program to control all functions, calculations, communications and built-in test facilities Power consumption 250 W/300 W with LM11 MTBF (MIL-STD-217E) > 13 700 hours RVR computer interface Modem CCITT V. 21 Dedicated line to RVR computer Without modem: RS-232C interface Maintenance terminal interface RS-232C, 300 baud Output message Visibility, transmittance values, luminance data (if connected), status data in ASCII Options Double baseline optics (LPO11) LM11 Background Luminance Meter LM11 BACKGROUND LUMINANCE METER Measuring range Accuracy Spectral response range Peak wavelength Field of view MTBF (MIL-STD-217E) Connection Mounting 4 . . . 700 nm 550 nm 5 degrees 183 000 hours To any LP11 Light Transmitter On top of LP11 by a screw VAISALA SA 3, Parc Ariane Saint-Quentin-En-Yvelines F-78284 Guyancourt Cedex FRANCE Phone (nat. ): (1) 3057 2728 Telefax: (1) 3096 0858 Head Office: VAISALA Oy PL 26, FIN-00421 Helsinki FINLAND Phone (int. ): (+358 0) 894 91 Telefax: (+358 0) 894 9227 Telex: 122832 vsala fi VAISALA GmbH Postfach 540267 D-22502 Hamburg DEUTSCHLAND Phone (nat. ): (040) 858 027 Telefax: (040) 850 8444 VAISALA (UK) Ltd Cambridge Science Park Milton Road Cambridge CB4 4GH UNITED KINGDOM Phone (nat. ): (01223) 420 112 Telefax: (01223) 420 988 VAISALA TMI Ltd Vaisala House 349 Bristol Road Birmingham B5 7SW UNITED KINGDOM Phone (nat. ): (0121) 683 1200 Telefax: (0121) 683 1299 VAISALA Inc. 100 Commerce Way Woburn, MA 01801 - 1068 USA Phone (nat. ): (617) 933 4500 Telefax: (617) 933 8029 VAISALA KK 42 Kagurazaka 6-Chome Shinjuku-Ku, Tokyo 162 JAPAN Phone (nat. ): (03) 3266 9611 Telefax: (03) 3266 9610 VAISALA Pty. 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