Transmissometer LT31

Accurate and reliable, WMO and ICAO compliant determination of the Runway Visual Range (RVR) reduces airport downtime and improves safety of operations. The Vaisala Transmissometer LT31 is the qualified observer of RVR providing correct visibility data without interruptions and with minimal maintenance.

Single baseline for the measurement range 10...10 000 m MOR
State-of-the-art white light source
Window contamination compensation
Sophisticated self-diagnostics
Internal back-up battery
Meets the ICAO ad WMO requirements for RVR and visibility
Based on decades of field experience
Compatible with Vaisala Transmissometer MITRAS and SKOPOGRAPH II Flamingo
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Key Benefits

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 (CAT I ... CAT IIIb), as well as the range required for Aeronautical Visibility (the ICAO defined visibility). The accuracy of the LT31 meets the ICAO and WMO requirements.
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.
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.
Automatic window contamination compensation
Window contamination is a significant source of error in transmissometers. Maintaining high accuracy has required frequent cleaning. However, the effects of contamination can be automatically compensated if the window transmittance can be measured accurately.
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 for transmissometers as narrow spectrum light source (e.g. lasers or colored LEDs) will cause measurement error with some weather phenomena.
Extensive self-diagnostics
The LT31 has a sophisticated self-diagnostics that provides detailed status information for all functional units. In addition, this feature helps to locate possible technical failures. It records a history of significant operational situations, warnings, and alarms from the instrument.

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