Chapter 4 ________________________________________________________________ Operation
VAISALA _______________________________________________________________________ 71
Returning to the normal autosend mode is done using the following
command:
CEILO >
set message transmission periodic
The polling string format is as follows:
<
Enq>
CL
IdNo
↵
where
Enq
=
Character ENQUIRE = ASCII 05H = control-E.
CL
=
Fixed ceilometer identifier; CL for CL31 messages, CT for
CT25K and CT25KAM messages.
Id
=
Identification character, 7-bit printable ASCII character.
No
=
Optional message identifier; 1 or 6 for CT messages and 1 or S
for CL messages. The CL identifier 1 returns the default option
for data message No. 1. To return a particular subclass message,
use one of the following identifiers: 11, 12, 13, 14, or 15. Data
message No. 2 is requested similarly: 21, 22, 23, 24, or 25.
↵
=
ENTER (Carriage Return) + Line Feed.
The following are examples of the polling command:
<
Enq
> CL112<Enter> Message 1, subclass 2 from ceilometer
No.1
<
Enq
> CT11<Enter>
CT25K Message 1 from ceilometer No.1
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.
LD40 message is polled by sending a LD40 Command Telegram.
Table 17 below describes the command telegram frame of a polling
request.
Table 17
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