Vaisala CL31 Technical data

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CL31 Ceilometer for Cloud Height Detection

The Vaisala Ceilometer CL31 is a
compact and lightweight instrument
for cloud base height and vertical
visibility measurements. It detects
three cloud layers simultaneously.
The CL31 employs a pulsed diode
laser LIDAR (light detection and
ranging) technology. The CL31 is
ideal for aviation and meteorological
applications.

Measurement starts from
ground level

The enhanced single-lens technology
applied in the CL31 ensures excellent
performance starting at a height of
virtually zero. This is due to the strong
and stable signal over the whole
measurement range. The single-lens
technology provides unsurpassed
reliablity during precipitation,
low clouds and ground based
obscurations, which are the most
critical phenomena in aviation safety.

Fast measurement

Fast measurement helps to detect
thin cloud patches below a solid
cloud base. The CL31 provides a
full backscatter prole for data
visualization and research purpose.

The CL31 beam can be directed either
vertically or tilted. The tilting option
together with the novel optics design
provides enhanced performance
during precipitation by improving the
protection given by the shield. In the
measurement unit, a tilt angle sensor
automatically corrects the measured
cloud distance reading to vertical
cloud base height.

Extensive self-diagnostics

The CL31 is fully automatic. In
addition to cloud height data, the
messages contain instrument status
information based on comprehensive
self-diagnostic routines. In case
of a malfunction the diagnostics
help users to identify the failed
module. The CL31 features practical
modularity and its easy-access door
ensures fast servicing and high data
availability.

Easy installation and
maintenance

The CL31 is easy to install. It has
a radiation shield that protects
the unit during precipitation and
against excessive heat or cooling in
extreme temperatures. 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.

Features/Benefits

Measurement range from 0 to

▪

7.5 km (from 0 to 25,000 feet)

Second-generation, advanced

▪

single-lens optics provides
excellent performance also at
low altitudes

Reliable operation in all

▪

weather; unsurpassed
performance in vertical
visiblity and cloud detection
during precipitation

Extensive self-diagnostics with

▪

fault analysis

Vaisala Ceilometer CL31 measures
cloud base height and vertical visibility
in all weather - good or bad.

Modular design for easy

▪

installation and maintenance

Fast measurement enables

▪

detection of thin cloud layers
below a solid cloud base

Latest technology from the

▪

world-leading manufacturer

- based on the experience
from more than 5000 installed
Vaisala ceilometers worldwide

Technical data

Performance

Measurement range 0 ... 25,000 ft. (7.5 km)
Reporting cycle programmable, 2 ... 120 s
Reporting resolution 5 m/10 ft., units selectable
Distance measurement accuracy against
hard target

greater of ±1 % or ±5 m
Laser InGaAs diode, 910 mm
Eye safety Class 1M IEC/EN60825-1

Electrical

Power (* 100/115/230 VAC ±10%,

50 ... 60 Hz

max. 310 W including heating

Interfaces

data RS232 / RS485 / Modem
maintenance RS232
baud rate

RS232 / RS485 300 ... 57,600
modem V.21, V.22, V.22bis 300 ... 2400

Back-up battery Internal, 2 Ah

Data messages

Cloud hits (up to 3 layers) and status information
Cloud hits, status and backscatter profile
Cloud hits and internal monitoring data
Emulation of CT12K, CT25K, LD-25/40
Sky Condition (optional)

Environmental

Temperature range -40 ... +60 °C (-40 ... +140 °F)
Humidity 0 ... 100 % RH
Wind 55 m/s
Housing classification IP65
Vibration Lloyds Register / IEC60068-2-6

5 ... 13.2 Hz ±1.0 mm

13.2 ... 100 Hz ± 0.79 mm
EMC IEC/EN 61326
Electrical Safety IEC/EN 60950

Accessories / 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 CLRADIOKIT
Graphical User Interface for Ceilometers CL-VIEW
Bird deterrent device CL31BIRDKIT

(* Please specify power and optional accessories when ordering.

Dimensions

Dimensions in mm

Mechanical

Dimensions

total 1190 x 335 x 324 mm
measurement unit 620 x 235 x 200 mm

Weight

total 32 kg

measurement unit 13 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. B210415EN-B ©Vaisala 2009

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of Vaisala or its individual partners. The reproduction, transfer,
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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.