Vaisala LM21 - PRODUCT OVERVIEW; LM21 Sensor Introduction

Chapter 2 ____________________________________________ Product Overview
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CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the LM21 Background Luminance
Sensor features, advantages, and the product nomenclature.
Introduction to LM21 Background
Luminance Sensor
LM21 Background Luminance Sensor is a part of the airport
RVR assessment equipment provided by Vaisala. The
background luminance has an effect on the distinctiveness
of the runway lights as seen by a pilot. LM21 measures the
total amount of light coming in from an angle of 6 degrees
and sends the measurement results to the interface unit of
FS11 Visibility Sensor via an RS-485 connection. LM21FD
and LM21MITRAS convert the measured background
luminance to frequency. The frequency can then be
converted to background luminance by FD12P Weather
Sensor or MITRAS Transmissometer.