The Vaisala C L 5 1 altimeter is capable of measuring high-altitude cirrus clouds or vertical visibility under adverse weather conditions through low and hollow cloud layers.
CL51 uses pulsed diode laser LIDAR (Laser Detection and Ranging) technology to emit short, powerful laser pulses in a vertical or nearly vertical direction. The laser reflection (backscattering) caused by clouds, precipitation, or other light shielding objects can be used to analyze and determine the height of the cloud base.

Measurement starts from the ground
The enhanced single lens technology used in CL51 ensures outstanding performance from absolute zero height measurement onwards. This is due to the strong and stable signal it obtains throughout the entire range. CL51 can simultaneously detect three cloud layers. If the cloud base is obstructed by precipitation or ground fog, it can also measure vertical visibility. CL51 can provide a full range backscatter profile, which provides the possibility for further boundary layer and atmospheric analysis.

Specially designed for harsh weather conditions
The CL51 has a protective cover with a window blower and heater, which ensures smooth operation even in precipitation and extreme temperatures. Optical filters provide it with sun protection. The tilted protective cover further shields it from the effects of precipitation and ice crystal mirror reflection. The tilt angle can be automatically adjusted.

self-diagnosis
In addition to cloud data, the C L 51 can also automatically output information about device status, which is based on its routine self diagnosis. When a malfunction occurs, this diagnostic program can help users identify the faulty module.

maintenance
The periodic maintenance of CL51 is generally limited to keeping the windows clean, and you do not need to adjust them on site. A window blower with a heater can improve its performance by keeping the windows dry and clean. Heating can prevent windows from frosting in cold conditions. When a malfunction occurs, it will automatically issue a report in the form of data or status information.

Performance advantages
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Cloud detection range up to 13 kilometers (43000 feet)
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The backscatter profile covers the entire distance up to 15 kilometers
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The second-generation advanced single lens optical components have the same performance in low altitude detection
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Practical verification shows that it can operate automatically 24/7 under all weather conditions
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Modular design, easy to install and maintain
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Rich self diagnostic program with fault analysis capability
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Reliable operation in all weather conditions: unparalleled performance under precipitation conditions
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Based on solid and low-cost laser diode technology ▪

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Detecting cirrus clouds
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The latest technology from world leading manufacturers, based on over 5000 Vaisala cloud altimeters installed around the world.