Vaisala FS11 - MESSAGE 2, FS11 with LM21

Chapter 4 _________________________________________________________________ Operation
VAISALA ________________________________________________________________________ 75
MESSAGE 2, FS11 with LM21
Message 2 is a message of fixed length where both visibility and
background luminance values are shown. The message 2 format is as
follows:
!
FSA
∀
VIS 02000 AL 0 BL 01000 AL 0
#
CSUM
∃−∗
where
!
=
Start of the heading (ASCII 1)
FS
=
FS11 sensor identifier
A
=
First character of the unit identifier, if the ID is not
defined it is replaced by a space character
∀
=
Start of the text (ASCII 2)
VIS 02000
=
Visibility identifier and MOR value, unit meter (SI-
unit), 1 min average
AL 0
=
Alarm status of the visibility sensor
BL 01000
=
Background luminance identifier and BL value, unit
cd/m
2
AL 0
=
Alarm status of the background luminance sensor
#
=
End of the text (ASCII 3)
CSUM
=
Checksum CRC16
∃
=
End of the transmission (ASCII 4)
−∗
=
CR + LF (ASCII 13 + ASCII 10)
The total amount of characters in the message is 41. The transmission
times are: 1.4 s at 300 bps (10-bit char), 0.17 s at 2400 bps, 0.042 s at
9600 bps.
For a list of alarm status code explanations, refer to Table 11 on page 74.
If only LM21 Background Luminance Sensor is connected to the
interface unit, it is recommended that the Visibility Sensor be disabled
using the Advanced Level Command SET VIS_SENSOR OFF. If the
Visibility Sensor is not disabled, the visibility value is missing and the
alarm status code is E (error). A sample message of a situation when only
LM21 is connected, but the Visibility Sensor is not disabled, is presented
in the following:
!
FSA
∀
VIS ///// AL E BL 01000 AL 0
#
CSUM
∃−∗
If the LM21 Background Luminance Sensor polling has been set on and
the alarm status code is E, the LM21 sensor could be missing or there
could be an EEPROM memory error in LM21.