 8329 Laser Ceilometer
Description
The Model 8329 Laser Ceilometer measures cloud height up to 12,500
feet by calculating the return time of laser light pulses reflected by the
cloud base. A low-power laser light transmitter utilizes a highly reliable
gallium arsenide diode to transmit the pulse signal to the cloud base. The
receiver is a silicon avalanche photodiode that incorporates an optical bandpass
filter to prevent interference from other light sources.
Features
The measuring cycle range can be evaluated in 15, 30, or 60 second intervals
in the 30 to 5,000 foot range, or 30, 60, or 120 seconds in the 30 to 12,500
foot range. Thus, tradeoffs can be made between measuring range and sample
rate, with slower rates conserving energy and extending laser diode life.
The ceilometer transceiver is enclosed in a rugged weatherproof housing,
which protects the unit in extreme operating conditions ranging from -55°
C to +55° C. Automatic sensing circuits control a high-pressure blower
unit to clear rain and snow from the tranasceiver windows. Heaters built into
the case are switched on when the internal temperature falls below 20°
C. Additional sensing circuits control the laser output power and the temperature
of the laser diode itself, in order to maintain the correct light wavelength.
The 8329 Laser Ceilometer provides two outputs: a built-in modem for long
distance data transmission, and RS232 output for shorter distance transmissions.
Each data signal includes measurement of up to two cloud base heights. If
no cloud base is detected, but conditions are obscured, the ceilometer will
indicate vertical visibility to 6,500 feet (2,000 m). Status information is
sent at regular intervals to assure the system is functioning properly. The
ceilometer will operate reliably on a 90-day maintenance cycle.
The Model 8329 Laser Ceilometer is manufactured to specifications established
by the FAA Automated Weather
Observing System (AWOS) and NWS Automated Surface Observing System (ASOS).
An MS-DOS based software package is available to provide a graphical and
numeric display of the sensor data.
|
