Vaisala LT31 Technical data
Vaisala Transmissometer LT31
RVR with New Eyes
Accurate and reliable determination
of the Runway Visual Range (RVR)
reduces airport downtime and
improves safety of operations.
The Vaisala Transmissometer LT31
is the qualied observer of RVR
providing correct visibility data
without interruptions and with
minimal maintenance.
Measurement Range
from 10 to 10 000 m
The LT31 provides the most
accurate and reliable solution for the
automatic measurement of RVR. The
Meteorological Optical Range (MOR)
measurement range is from 10 to
10 000 meters, which covers the full
required RVR range (CATI ... CATIIIb),
as well as the range required for
Aeronautical Visibility (the ICAO
dened visibility). The accuracy of
the LT31 meets the ICAO and WMO
requirements.
This full measurement range is
achieved with a single baseline
system, which makes measuring
easier and more economical.
The Vaisala Transmissometer LT31 enables the accurate and reliable single baseline
measurement for CATIIIb category airports.
www.vaisala.com
White LED Provides Wide
Spectrum Light Source
The LT31 incorporates a white
LED as a light source. White light
is needed for the best accuracy
in transmittance measurement.
The WMO recommends the use
of a wide spectrum (white) light
sources (e.g. lasers or colored LEDs)
for transmissometers as narrow
spectrum light source will cause
measurement error with some
weather phenomena.
Features/Benefits
Single baseline for the
▪
MOR measurement range
10 ... 10 000 m
State-of-the-art white light
▪
source
Automatic alignment with
▪
quality control as a standard
feature
Automatic calibration as a
▪
standard
Internal back-up battery
▪
Compatible with Vaisala
▪
Transmissometer MITRAS and
SKOPOGRAPH II Flamingo
Window contamination
▪
compensation
Meets the ICAO and WMO
▪
requirements for RVR and
visibility
Based on decades of field
▪
experience
Sophisticated self-diagnostics
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Automatic Calibration with Integrated
Forward Scatter Sensor
Calibration of a transmissometer is traditionally
based on human observations. A reliable and accurate
calibration has required very high visibility, stable
conditions, and skilled and well trained personnel.
The Vaisala patented automatic calibration method for
transmissometers is based on an integrated forward
scatter sensor/present weather sensor. The system
automatically detects drift and adjusts the sensor
settings accordingly. Weather conditions do not need
to be as good as for manual calibration; the LT31
automatically recognizes suitable conditions.
Automatic Fine Alignment
One of the major error sources in transmittance
measurement is alignment drift. Checking and adjusting
the alignment has also required skilled and trained
personnel.
To maintain the measurement accuracy, the LT31
performs an automatic optimization of the alignment.
The alignment quality is also continuously evaluated
without any human intervention.
The integrated forward scatter sensor.
The automatic ne alignment also provides easy handling
of the LT31 during installation. The alignment quality
during harsh weather conditions is ensured by a double
mast construction. The outer tube works as wind and
solar radiation shield. The inner support structure is
separated from thermal and mechanical stress caused by
solar radiation and wind load.
Contamination Reduction
In general, precipitation leads to an increased amount of
window contamination. The LT31 has long and narrow
weather protection hoods that reduce the amount of
window contamination caused by precipitation.
For wind driven precipitation or dust, the instrument is
equipped with a powerful blower. The blower creates
an air curtain in front of the instrument window. The
air curtain is specially designed not to disturb the
measurement path and cause the measurement errors that
have been a problem with conventional blower designs.
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