Vaisala CT25K - Page 51

Ceilometer CT25K
CT25K-U059en-2.1 User’s Guide
37
Interpretation of the message is as follows:
1ST LINE
Identical to that of message no. 1 except that the second to last digit which
identifies the message number is always 2.
2ND LINE
Identical to that of message no. 1
3RD LINE
Example: 100 N 53 +34 204 146 +2 621 LF7HN1 139↵
Measurement parameters are mostly in engineering units. Plus and minus
signs are possible. Out-of-Range is indicated by slashes (/////). Contents:
100 Parameter SCALE, 100 (%) is normal (0...999 possible)
N measurement mode; N = Normal,
(C = Close range, not available in CT25K)
53 laser pulse energy, % of nominal factory setting (0...999)
+34 laser temperature degrees C (-50...+99)
204 receiver sensitivity, % of nominal factory setting (0...999)
146 window contamination, millivolts at internal ADC input (0...2500)
+2 tilt angle, degrees from vertical (-15...+90)
621 background light, millivolts at internal ADC input (0...2500)
LF7HN1 measurement parameters (pulse Long/Short, freq F (const.), pulse qty
4
7+1
, gain High/Low, bandwidth Narrow/Wide, sampling 10/20 MHz)
139 SUM of detected and normalized backscatter, 0...999.
Multiplied by scaling factor times 10
4
. At scaling factor 100 the
SUM range 0...999 corresponds to integrated backscatter
0...0.0999 srad
-1
4TH...19TH LINE
Backscatter profile, sensitivity and range normalized, at 100 ft = 30 m
resolution, normally scaled to units of (10000·srad·km)
-1
Example of 8th line:
064FDFDFDFDFDFCFCFCFCFCFCFCFCFBFBFBFBFBFBFBFAFBFAFBFBFAFAFBFAF9FAF9↵
where:
064 is start distance (height) of line backscatter data items;
decimal, unit is 100ft = 30m = 200ns (two-way)
FDFC, FBFA, ... are 16 four-character data items per line, at 100ft =
30m = 200ns resolution; 16-bit HEX-ASCII; msb
nibble and bit first. 2's complement. Data is range
and sensitivity normalized backscatter, units
(10000·srad·km)
-1
unless otherwise scaled by
parameter SCALE