Chapter 5 _________________________________________________________ Theory of Operation
VAISALA _______________________________________________________________________ 111
Calculations
The FS11 software calculates the extinction coefficient from the samples
by separating the signals coming from droplets and other scattering
media. The extinction coefficient is calculated separately for droplets and
other scattering media, and these are summed using weights. MOR is
calculated from the summed extinction coefficient with the following
known formula of the 5% contrast ratio:
MOR = -
ln0.05 / σ = 3 / σ
where σ is the extinction coefficient.
Internal Monitoring
Extensive built-in tests are included in the FS11 operation. Various
voltages are measured, and corresponding alarm and warning limits are
checked.
The FS11 sensor generates a warning if some monitored value does not
meet the criteria for optimal operation, but the measurement results are
still reliable. For example, slightly contaminated windows or aging
transmitter LEDs generate warnings. If a critical hardware failure is
detected, the sensor indicates an alarm and the corresponding data is set
as missing (/////).
Built-in tests include contamination monitoring, signal monitoring,
hardware monitoring, and memory tests. The results of the monitoring
are displayed in the status message.
FS11 Status Messages
The status messages display the results of the built-in test system. A short
status check message shows a quick report of the system status. The short
status message is requested with command
STATUS CHECK
:
0> status check
FS11 SYSTEM STATUS: OK
Measurement unit: OK
Current Events:
NONE.
Interface unit: OK
Current Events:
Conf2:VIS+ALS measurement
Background luminance sensor: OK
Current Events:
NONE.
