Vaisala LD-40 Technical data

Vaisala LD-40 Ceilometer

Cloud Height Measurement

up to High Cirrus

• 13,000 m (43,000 ft)
measurement range

• Cirrus cloud detection at
high altitude

• Sophisticated algorithms
for cloud detection

• No need for field adjustments

• Modular design: subassemblies are
easily replaced in the field without
optical realignment

The Vaisala LD-40 "Tropopauser" is a compact,
long-range ceilometer for cloud detection and
atmospheric profiling. Operating up to to an
altitude of 43,000 feet (13 km), the vertical
resolution of the instrument is 25 feet (7.5 m).
The measurement principle is based on LIDAR
(Light Detection and Ranging). Short pulses of
light are emitted by a laser diode, focused to a
parallel beam, and then transmitted vertically into
the atmosphere. Part of the light is scattered back
to the ceilometer from the aerosols in the
atmosphere.

HIGH PERFORMANCE UNDER ALL KINDS OF
PRECIPITATION

Using the backscatter signal, the LD-40 calculates
cloud height, the maximum detection range,
vertical visibility, and provides precipitation
status. The standard report includes height values
for up to 3 cloud layers. The long measurement
range allows cirrus clouds to be detected at high
altitude. Sophisticated algorithms are employed
to ensure reliable cloud detection under all kinds
of precipitation. When a cloud base cannot be
distinguished during weather conditions
associated with very low visibility, vertical
visibility is still reported. The LD-40's ability to
report raw data also makes it a valuable tool for
atmospheric research.

MINIMAL MAINTENANCE WHATEVER THE
CLIMATE

The LD-40 operates unattended under all climatic
conditions. Internal monitoring ensures reliable
operation: messages are automatically transmitted
containing information on internal diagnostics.
The LD-40 can be operated as a stand-alone
instrument or as part of a large meteorological
system. Its design is modular: subassemblies such
as the laser transmitter are easily replaced in the
field without optical realignment.

TECHNICAL INFORMATION

PERFORMANCE

Measurement range

25 ft to 43,000 ft (8 m to 13,000 m)
Resolution 25 ft (8 m)
Accuracy (solid target) ± 25 ft (8 m)
Measurement cycle 15 seconds
Laser Stacked diode, InGaAs (MOCVD)
Wavelength 855 nm
Eye safety

Class 3A (EN60825-1)

Output

Height of cloud base, up to 3 layers

Maximum range of detection

Vertical visibility

Backscatter profile

Instrument status information

ELECTRICAL

Power supply 230 / 115 VAC +10% -15%
Power consumption

700 W max. including heating

I/O connections

Data line: RS232/RS422/RS485/modem

Maintenance line: RS232

MECHANICAL

Dimensions 1260 (h) x 444 (w) x 404 (d)
Weight 40 kg

ENVIRONMENTAL

Operating temperature -40 to 55 °C
Operating humidity up to 100 % RH
Wind 55 m/s
Electrical safety EN 60 950

ACCESSORIES

Cloud Height Simulator for operational testing in
field conditions
Solar shutter for protecting against direct solar
radiation
Service tool set

Power, data line and accessories are to be
specified when ordering

Vaisala Oyj

P.O.Box 26
FIN-00421, Helsinki
FINLAND
Phone: [phone]
Telefax: ([phone]

Ref. B210254en-A