The Mierij Meteo MV 11 Visibility Sensor is designed to monitor visibility conditions over a range of 0-16 km.
The MV 11 includes both analog and digital outputs. Analog output ranges of 0-1, 0-5 or 0-10 volts and 4-20 mA are available. Also included are alarm outputs, which can be adjusted to alarm at user preset visibility thresholds. Two alarm channels are standard, making it possible to indicate Good/Medium/Poor Visibility by setting the appropriate thresholds. Digital RS232 and RS485 output at 300-38k4 Baud can be used to indicate the present visibility and provide diagnostic information.
Visibility is detected using widely accepted principles of forward scattering. A high output infrared LED transmitter projects light into a sample volume and light scattered in a forward direction is collected by the receiver. The light source is modulated to provide excellent rejection of background noise and natural variations in background light intensity. The sensor’s analog output signal is proportional to visibility. Visibility is also compared to the preset alarm thresholds, so that when alarm conditions are reached, the outputs are switched. Visibility thresholds can be set to any value within the instrument range. Alarm outputs are toggled from 0 to 5 V, or from 5 to 0 V, when the alarm condition is satisfied.