How do you measure visibility? What instrument is used to measure visibility?

Visibility is the distance at which objects can be clearly seen and distinguished in the atmosphere due to the obscuring effect of particles such as fog, dust, smoke or water droplets. Typically, visibility is measured in meters (m). Below are several common methods of measuring visibility and the instruments used to do so:

Visual Method: Visibility is estimated by the maximum horizontal distance from the ground at which a person with normal vision would observe the outline of a target under the prevailing weather conditions. Manual observation is also a common method of measuring visibility in some situations, such as weather stations and airports. Staff estimate the visibility range by observing the visibility of distant objects with the naked eye.

Atmospheric Transmissometer: This is an instrument that measures atmospheric transmittance and can be used to measure visibility. It measures atmospheric transmittance by transmitting and receiving an infrared beam to calculate visibility.

Automatic Laser Visibility Meter: This is an instrument that measures visibility using the principle of laser scattering. It calculates visibility by emitting a laser beam and measuring the intensity of the scattered light from the returned laser beam.

Visibility Sensors: Visibility sensors are one of the common instruments used to measure visibility, they indirectly calculate visibility by measuring the scattering and absorption of light to determine the concentration of particulate matter in the air. Such sensors usually utilize a laser or infrared light source and are equipped with a photodetector to measure changes in the intensity of light.

LIDAR: LIDAR can be used to determine the concentration and distribution of particulate matter in the atmosphere by sending out laser pulses and measuring their return time, thus calculating visibility. Lidar is commonly used for long range, high accuracy visibility measurements, such as in airport weather monitoring.

 Sight meter: A sight meter is an instrument specifically designed to measure visibility, usually using optical principles to determine visibility by looking at the furthest distance the human eye can see. This method is often used in ground meteorological observations and vehicle navigation systems. 

These methods and instruments can be selected according to specific application needs, and some methods require specialized equipment and training to make accurate measurements. In practical applications, it is important to select the appropriate visibility measurement methods and instruments to ensure that accurate and reliable measurement results are obtained. The above information is for reference only, if necessary, we recommend you to consult professional and technical personnel.

Visibility Sensor Datasheet

NBL-W-VS-Visibility-Sensor-Instruction-Manual.pdf