Lufft CHM 15k Nimbus, Manual

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Communication RS485 & Ethernet
Revision R09, November 2016 45
8.3.5 Raw Data Telegram
Raw data are output in NetCDF-format that is explained in chapter 8.4. NetCDF
is a binary format. For tranfer via RS485/ RS232 it has to be converted into 7-bit
ASCII code (21 to 60 HEX range) using UUencode to be able to handle special
characters like <STX> or <EOT>.
The NetCDF-file of a raw data set is about 14 kByte long. UUencode transforma-
tion turns these into 20 kB of ASCII data that need to be transmitted. With a
baud rate setting of 9.6 kbps =1.2 kBps), transmission takes about 16 seconds,
which results in the following additional restrictions on automatic raw data tele-
gram outputs as shown in table 11.
Table 12 describes the structure of additional data in a raw data telegram.
Detector temperature
Temperature measured at the sensor:
displayed in Kelvin x 10; ±2 K
NN1 unassigned
NN2 unassigned
Laser operating time (h) Laser lifetime hours of operation
Optics status
Degree of contamination of glass panel in percent
100 = transparent, 0 = opaque
Laser pulse number Number of laser pulses in logging interval (7-digit)
Receiver status
For tracking of optical beam path and receiver status.
100 = maximal sensitivity
0 = sensitivity down to zero
Light source status
Evaluates lifetime and stability of the laser light source
temperature, current stability, repetition rate;
100% = starting value, <20 = laser switches off
Baud rate
no.
Baud rate [kbps] logging time interval (dt(s))
0 1.2 Not available
1 2.4 Not available
2 4,800

40 s
3 9,600

20 s
4 19,200

10 s
5 38,400

5 s
6 57,600 No further restrictions
7 115,200 No further restrictions
Table 11: Additional restrictions
Term Explanatory note
Table 10: Terms in extended data telegram