Sentry™ Tunnel Visibility Sensor

73200-56

The Sentry™ Tunnel Visibility Sensor has been installed in road
tunnels in many countries including Spain, United Arab Emirates,
The Netherlands, and Saudi Arabia. The function of the Sentry™
is to optically measure atmospheric visibility.

The Sentry™ uses the forward scatter measurement of
atmospheric extinction coefficient to determine the visibility in
the tunnel. Forward scatter is accepted worldwide as the most
practical method of measuring visibility. It measures the intensity
of the light scattered by the dust particles illuminated by an
incident beam of infrared light. Because there is no need for a long
measuring distance, measurement takes place in the local area of
the Sentry™.