Operating Manual CHM 8k
R1.7 / 01-2020
Communication via RS485 & Ethernet
34
Byte
Value
Description
33-37
****
Cloud layer 2
38
<SPACE>
20 HEX
39-43
*****
Cloud layer 3
44
<SPACE>
20 HEX
45-48
****
Penetration depth of the laser beam in cloud layer 1
49
<SPACE>
20 HEX
50-53
****
Penetration depth of the laser beam in cloud layer 2
54
<SPACE>
20 HEX
55-58
****
Penetration depth of the laser beam in cloud layer 3
59
<SPACE>
20 HEX
60-64
*****
Vertical visibility
65
<SPACE>
20 HEX
66-70
*****
Maximum detection range
71
<SPACE>
20 HEX
72-75
****
Altitude (cloud height offset)
76
<SPACE>
20 HEX
77, 78
**
Unit (ft/m), ft or m<SPACE>
79
<SPACE>
20 HEX
80, 81
**
Sky condition index
82
<SPACE>
20 HEX
83-90
********
System status: 32 Bit status code
91
<SPACE>
20 HEX
92, 93
**
Checksum (two's complement of the sum of bytes 0 to 96
expressed in hex code, excluding bytes 92 and 93)
94
<CR>
0D HEX
95
<LF>
0A HEX
96
<EOT>
04 HEX
Table 8 Standard data telegram format; * = any character.
Up to three cloud heights are reported in the standard telegram. If less than three cloud heights are
detected, the text
NODET
appears in the remaining fields. If cloud penetration depths are not determined,
the text
NODT
appears in the corresponding fields.
A
NODET
value is also reported in the protocol if the algorithm is unable to calculate the following values:
•
Visibility
•
Maximum detection range
If the values cannot be determined due to a device error, the fields are filled with a minus sign "-" or a
slash "/" (see section 8.4.5). Detailed information on the type of device error can be found in the status
codes (see section 8.5).
Correction of the measured cloud height
The cloud height is usually measured from the bottom of the device. If the parameter
"altitude(m)" is set to a value other than zero and "usealtitude" is set to 1, the cloud
height is corrected by this factor. Instead of the relative height axis an absolute altitude
axis is used. In the NetCDF data, the variable CHO indicates whether the parameter
"usealtitude" is set.
8.3.4 Extended data telegram
The extended data telegram consists of 240 Bytes, if the default number for the reported cloud layers of
3 is selected, see Table 9
The number of cloud layers is
specified in the parameter “Layer (NoL)”, see