Vaisala CL51 Technical data

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CL51 Ceilometer for High-Range Cloud Height
Detection

The Vaisala Ceilometer CL51 is
designed to measure high-range
cirrus cloud heights without
surpassing the low and middle layer
clouds, or vertical visibility in harsh
conditions.

The CL51 employs a pulsed diode
laser LIDAR (Light Detection And
Ranging) technology, where short,
powerful laser pulses are sent out in
a vertical or near-vertical direction.
The reection of light (backscatter)
caused by clouds, precipitation or
other obscuration is analyzed and
used to determine the cloud base
height.

Measurement from the
ground level

The enhanced single lens technology
applied in the CL51 ensures excellent
performance starting at a height
of virtually zero. The signal is
strong and stable over the whole
measurement range.

The CL51 is able to detect three cloud
layers simultaneously. If the cloud
base is obscured due to precipitation
or ground-based fog, the CL51
reports Vertical Visibility. The CL51
is able to provide the backscatter
prole over the full measurement
range. This information provides a
possibility for an advanced boundary
layer and atmospheric analysis.

Designed for harsh
weather

The CL51 has a shield with a
blower and heater, which allows
steady operation in precipitation
and under extreme temperatures.
Reliable solar protection is ensured
by optical lters. A tiltable shield
further protects the instrument

from precipitation and specular
reection from ice crystals. The tilt
angle measurement and correction is
automatic.

Self-diagnostics

In addition to cloud height data,
the fully automatic CL51 outputs
messages with information on the
instrument status. The information
is based on comprehensive self­diagnostic routines. In case of a
malfunction the diagnostics help the
user to identify the failed module.

Maintenance

Periodic maintenance of the CL51 is
normally limited to window cleaning.
There is no need for adjustments
in the eld. The automatic window
blower with heater improves
performance by keeping the window
clean and dry. In cold conditions
heating prevents frost generation
on the window. Any malfunction is
automatically reported in the data
and status messages.

Features/Benefits

Cloud reporting range up to

▪

13 km (43,000 feet)

Second-generation, advanced

▪

single-lens optics with
excellent performance also at
low altitudes

Modular design for easy

▪

installation and maintenance

Reliable operation in all

▪

weather: unsurpassed
performance in precipitation

Detection of Cirrus clouds

▪

CL51

Backscatter profiling over full

▪

range up to 15 km

Field-proven, fully automatic

▪

24/7 operation in all weather
conditions

Extensive self-diagnostics with

▪

fault analysis

Based on robust and

▪

aordable laser diode
technology

Latest technology from the

▪

world leading manufacturer

- installed base over 5,000
Ceilometers worldwide

Technical data

Performance

Cloud reporting range 0 ... 13 km (0 ... 43,000 ft.)
Backscatter profiling range 0 ... 15 km (0 ... 49,200 ft.)
Reporting cycle programmable 6 ... 120 s,

or polling
Reporting resolution 10 m /33ft, units selectable
Distance measurement accuracy

against a hard target greater of ±1% or ±5 m
Laser InGaAs diode, 910 nm
Eye safety Class 1M IEC/EN 60825-1

Electrical

Power (* 100/115/230 VAC

±10 %, 50 ... 60 Hz

max. 310 W incl. heating

Interfaces

Data RS232/RS485/Modem

Maintenance RS232

Bits per second

RS232/RS485 300 ... 115,200
Modem V.21, V.22, V.22bis 300 ... 2400

Backup battery Internal, 2Ah

Data messages

Cloud hits (up to 3 layers) and status information
Cloud hits, status and backscatter profile
Emulation of CL31 and LD-40
Sky Condition (optional)

Environmental

Temperature range -55 ... +60 °C (-67 ... +140 °F)
Humidity 0 ... 100 %RH
Wind 55 m/s
Housing classification IP65
Vibration Lloyds Register/IEC 60068-2-6
EMC IEC/EN 61326
Electrical safety IEC/EN 60950

Accessories and options (*

Cable termination box Termbox-1200 with extra transient
protection
PC maintenance cable QMZ101
Shock absorbing mounting pad CT35022 for ship installations
Modem module DMX501
Attachment mechanics for radio modem antenna CL51RADIOKIT
Graphical User Interface for Ceilometers CL-VIEW
Bird deterrent device CL51BIRDKIT

(* Please specify power and optional accessories when ordering.

Mechanical

Dimensions

Total 1531 x 364 x 354 mm

Measurement unit 834 x 266 x 264 mm
Weight

Total 46 kg

Measurement unit 18.6 kg
Tilt positions Vertical or 12° tilted
Automatic window blower/heater
Radiation shield and pedestal
Service access through a door
Optical filters for protection against direct sunlight

For more information, visit
www.vaisala.com or contact
us at [e-mail]

Ref. B210861EN-A ©Vaisala 2010

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in any form without the prior written consent of Vaisala is strictly
prohibited. All specifications — technical included — are subject
to change without notice.