Campbell Scientific CSAT3 3-D Sonic Anemometer - Manual (Page 63)

Appendix B. Serial Communications with the CSAT3
TABLE B-6. Converting Speed of Sound from Word 3
Conversion Output Resolution
(mm s –1 ) (°C @ 25 °C)
speed of sound (m s –1 ) = word 3 ∗ 0.001 + 340.0 1 0.0017
B.4 Word 4
Word 4 contains diagnostic information and the reporting range of u
x
, u
y
, and
u
z
wind speed. The diagnostic flags, bits b15 through b12, describe the status
of the anemometer (TABLE B-7). A flag is on if the bit is set high. All the
flags are on while the anemometer is acquiring signals or is in a lost trigger
state (TABLE B-8).
TABLE B-7. Decoding the Diagnostic Flags from Word 4
Bit Set High Description Comment
b15 Difference in the speed of sound between
the three non orthogonal axes is greater
than 2.360 m s –1
(~ 4 °C @ 25 °C)
The anemometer path length may have been altered
or the anemometer head is broken.
b14 Poor signal lock There may be an obstruction in the anemometer path
or on the transducer face.
b13 Sonic signal amplitude too high An obstruction, in the anemometer path or on the
transducer face, was removed.
b12 Sonic signal amplitude too low There may be an obstruction in the anemometer path
or on the transducer face.
Bits b11 through b06 are used in determining the range of the wind speed
reported in words 0 through 2.
Bits b05 through b00 are a diagnostic counter. This counter increments once
per measurement. The minimum value is 0 and the maximum is 63. The
counter wraps from 63 to 0 when the maximum value is incremented by one.
TABLE B-8. Special Case – Not a Number
Not a Number Word 0 Word 1 Word 2 Word 3 Word 4
Conditions hex base 10 hex base 10 hex base 10 hex base 10 hex base 10
Not Available 8000 -32768 8000 -32768 8000 -32768 8000 -32768 F03F 61503
Lost Trigger 8000 -32768 8000 -32768 8000 -32768 8000 -32768 F000 61440
B.5 CSAT3 RS-232 Status Format
The CSAT3 returns a 10 ASCII byte status in response to a “S” or “P”
command. This status provides information on the CSAT3’s Trigger Source
and the Execution Parameter. It also indicates if the analog outputs are on/off,
if the CSAT3 is reporting good data, and serial number of the CSAT3. This
software serial number matches those on the anemometer head and electronics
box.
B-5