Operating Manual CHM 8k
R1.7 / 01-2020
Communication via RS485 & Ethernet
37
Byte
Value
Description
228
;
3B HEX
229
*
Quality index aerosol layer 2
230
;
3B HEX
231
*
BCC; Base Cloud Cover
232
;
3B HEX
233
*
TCC; Total Cloud Cover
234
;
3B HEX
235-236
**
Checksum (two's complement of the sum of bytes 0 to 239 expressed in
hex code, excluding bytes 235 and 236)
237
<CR>
0D HEX
238
<LF>
0A HEX
239
<EOT>
04 HEX
Table 9 Extended data telegram format (see also Table 10); * = any character.
For the stated standard deviations of the individual quantities, the same exception values
"NODET/NODT/---" apply as for the corresponding basic quantities (see sections 8.3.3 and 8.4.5).
Further system parameters
The system parameters for data evaluation, including penetration depth, are explained
in section 9 Data Evaluation / Sky Condition Algorithm (SCA).
Designation
Description
Outside temperature
The measured outdoor temperature at the bottom of the unit. The
measured values are displayed in Kelvin x 10.
Error tolerance ± 5 K
Inside temperature
Measured temperature at the sensor. The measured values are
displayed in Kelvin x 10.
Error tolerance ± 2 K
Detector temperature
Measured temperature at the sensor. The measured values are
displayed in Kelvin x 10.
Error tolerance ± 2 K
NN1
Not used
NN2
Not used
Laser operating hours (h) Operating time of the laser in hours
Optics status
Degree of contamination of the glass window in percent
100 = clear view, 0 = opaque
Laser pulse number
Number of laser pulses in the measuring interval (7 digits)
Receiver status
Evaluation of the status of the optical path and receiver
100 = maximum sensitivity
0 = no sensitivity
Light source status
Evaluation of the lifetime and stability of the laser
Table 10 Designations in the extended data telegram.
8.3.5 Raw data telegram
The raw data is output in NetCDF format (for a description see 8.4 Structure of the NetCDF format).
NetCDF is a binary format. For transmission via RS485 / RS232, a transmission in a 7-bit ASCII code
(range 21 to 60 HEX) with UUencode is required to be able to handle none printable characters such as
<STX> or <EOT>.
The size of the NetCDF file of a raw data set is approximately 14 KByte. The UUencode conversion
produces 20 KByte of ASCII data which has to be transferred. At a baud rate of 9,600 bit/s, the