Vaisala FD12P - Manual (Page 25)

Chapter 2 ___________________________________________________________Product Overview
VAISALA ________________________________________________________________________ 25
The output data:
- Automatic or polled data message
- Visibility, present weather, precipitation and status data
- Automatic message type and interval is selectable at 15
seconds to n × 15 seconds (n < 18) intervals
The analog visibility output:
- Selectable range and mode (linear or logarithmic)
- Status control bit for remote alarm relay, etc.
- Alarms and warnings (hardware failures, visibility limits)
Optical Specifications
Operating principle:
- Forward scatter at an angle of 33o and capacitive rain sensor.
The light transmitter:
- Light source: near-infrared LED
- Peak wavelength: 875 nm
- Modulation frequency: 2.3 kHz
- Transmitter lens diameter: 71 mm
- Reference photodiode: for light source control
- Backscatter photodiode: for contamination and blockage
measurement
The light receiver:
- Photodiode: PIN 6 DI
- Spectral response: max. responsivity at 850 nm, 0.55 A/W
(in range 550 ... 1050 nm over 0.3 A/W)
- Reception lens diameter: 71 mm
- Backscatter light source: near-infrared LED for
contamination and blockage measurement