Chapter 5 ________________________________________________________________ Operation
VAISALA ______________________________________________________________________ 179
Message 7 - MITRAS Emulation
For compatibility on the system level, LT31 also supports the message
format, frames, and polling format of Vaisala MITRAS
Transmissometer. The MITRAS polling format is accepted only when
the MITRAS message emulation is selected with the SET MESSAGE
TYPE MITRAS command.
The MITRAS polling format is the following:
P<Space><ID>-*.
The emulated Vaisala MITRAS Transmissometer message is presented
below:
"ID 1 V 4550 B ///// S010101 -*#
------------------------------------
¦ ¦ ¦ ¦ ¦ ¦ ¦¦ ¦ ¦___receiver 2 status (fixed to 01)
¦ ¦ ¦ ¦ ¦ ¦ ¦¦ ¦___receiver 1 status
¦ ¦ ¦ ¦ ¦ ¦ ¦¦___transmitter status
¦ ¦ ¦ ¦ ¦ ¦ ¦____S, status heading
¦ ¦ ¦ ¦ ¦ background luminance value
¦ ¦ ¦ ¦ ¦___B,background luminance heading
¦ ¦ ¦ ¦_____ visibility m, 1 min average
¦ ¦ ¦________V, visibility heading
¦ ¦________unit ID (one character only)
¦_________ID, start indicator
The total amount of characters in the message is 35. The transmission
times are: 1.2 s at 300 bps (10-bit char), 0.15 s at 2400 bps, 0.04 s at
9600 bps.
The binary status is in hexadecimal notation. The status bits emulate the
MITRAS status as follows.
The transmitter status correspondence between MITRAS and LT31 is the
following:
BIT MITRAS LT31
BIT.0=1 MEAS MODE ON
II BIT.1=2 CONT/OTHER OFF
BIT.2=4 OPTICAL SURFACE Window contamination
BIT.3=8 POWER SUPPLY Power supply failure
BIT.4=1 HEATING OFF
I BIT.5=2 FLASH LAMP LED failure
BIT.6=4 BL METER BL sensor status (ON/OFF)
BIT.7=8 MEASUREM. LOOP
SIGNAL
OFF
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