Vaisala Background Luminance Sensor LM21

The LM21 features:

• Verified accuracy and photopic response
• Extensive self-diagnostics
• Window contamination measurement and compensation
• Optical path blockage detection
• High power heaters to prevent snow accumulation
• Calibration traceable to measurement standards
• Easy-to-use field calibration device available

It integrates with the Vaisala Transmissometer LT31 and Vaisala Forward Scatter FD70, FS11, or FS11P to create an expanded runway visual range (RVR) system.

COMPREHENSIVE SELF DIAGNOSTICS

To ensure reliable and uninterrupted operation, the LM21 has extensive self-monitoring functions and high-power heating features built into its design. Optical path clearance monitoring circuitry verifies measurements are not affected by obstructions. Attenuation compensation for window contamination ensures measurement accuracy between window cleanings, and also extends the cleaning interval.

EASY CALIBRATION

The calibration of LM21 is traceable to international measurement standards for luminous intensity. The calibration coefficients for light intensity have been defined during factory calibration and stored in the LM21 memory. Quick field calibration can be done using a unique field calibration device (LMA21) that provides a stabilized and diffused white light beam for LM21 calibration. Calibration starts automatically when the calibration unit is connected.