Vaisala CL31 - Table 20 Command Telegram Description Polling Request

USER'S GUIDE____________________________________________________________________
90 __________________________________________________________________ M210482EN-D
NOTE
If the id character in a polling string is replaced with a blank space, all
ceilometers on the line will respond. Accordingly, if No is a blank space,
CL31 sends the default message. In RS-485 mode id is always needed,
the blank space is ignored.
LD40 message is polled by sending an LD40 Command Telegram. See
Table 20 below for a description of the command telegram frame of a
polling request.
Table 20 Command Telegram Description 'Polling Request'
Byte Example Description
0 <STX> 02 HEX (Start of text)
1 H Command telegram header
2 0 Command telegram header
3 C Command telegram header
4 ! Command telegram header
5 X Instrument type --> Ceilometer
6 1 Sensor Id number (0 to 9..ABC..MIN). In this
case --> 1
7-17 P---------- Command indicator --> P (polling), byte 8-17
not used and filled with '-'
18-19 83 Checksum (Hex-coded two's complement of the
sum of bytes from 0 to 20, excluding bytes 18
and 19.
20 <EOT> 04 Hex (End of transmission)