Vaisala FD12P - Manual (Page 76)

User's Guide _______________________________________________________________________
76 ______________________________________________________ M210296en-A
parameter value relates to the square of droplet radius. The
relationship is the following:
X = 240 × R 2
where
X =
Parameter value
R = Droplet radius
Parameter value 30 would correspond to about a 0.7-mm droplet
diameter.
Heavy Drizzle Limit
The Heavy drizzle limit parameter refers to the minimum number of
drizzle droplets detected in 15 seconds. They must be detected before
drizzle becomes heavy (dense).
Light Drizzle Limit
The Light drizzle limit parameter defines the maximum number of
droplets detected in 15 seconds, when drizzle is light.
Snow Limit
The Snow limit parameter specifies the minimum ratio of optical
precipitation intensity to surface sensor (DRD12) precipitation
intensity, when the precipitation is snow. A half of this value is used
for separating sleet and ice pellets.
The typical value for Snow limit is 5. A smaller value directs the
FD12P to report more wet precipitation as snow.
Heavy Snow Limit
The Heavy snow limit parameter defines the minimum visibility (m)
on a two-minute average in heavy snow.
Light Snow Limit
The Light snow limit parameter defines the maximum visibility (m) on
a two-minute average in light snow. If snow is detected and the two-
minute visibility average is between the above heavy and light snow
limits, snow intensity is moderate.