Campbell Scientific CSAT3 3-D Sonic Anemometer - Manual (Page 62)

Appendix B. Serial Communications with the CSAT3
TABLE B-2. RS-232 Output
Word 0 Word 1 Word 2 Word 3 Word 4
b15 - b0 b15 - b0 b15 - b0 b15 - b0 b15 b14 b13 b12 b11 b10 b09 b08 b07 b06 b05 - b00
u
x
wind u
y
wind u
z
wind c diagnostic flags u
x
range u
y
range u
z
range counter
B.3 Words 0 through 3
The u
x
, u
y
, and u
z
wind speeds are reported on one of four different ranges.
This range is given by bits b11 through b06 in word 4. In order to decode the
wind speed, first look at the wind speed range code, then decode the data with
the appropriate equations given in TABLE B-3 through TABLE B-6. The data
in words 0 through 3 must first be converted into a base 10 representation
before applying the equations in TABLE B-3 through TABLE B-6.
TABLE B-3. Converting u
x
Wind from Word 0
Range Word 4 Range Code Conversion Output Resolution
b11 b10 (mm s –1 )
0 1 1 u
x
wind (m s –1 ) = word 0 ∗ 0.001 ∗ 0.25 0.25
1 1 0 u
x
wind (m s –1 ) = word 0 ∗ 0.001 ∗ 0.50 0.50
2 0 1 u
x
wind (m s –1 ) = word 0 ∗ 0.001 ∗ 1.00 1.00
3 0 0 u
x
wind (m s –1 ) = word 0 ∗ 0.001 ∗ 2.00 2.00
TABLE B-4. Converting u
y
Wind from Word 1
Range Word 4 Range Code Conversion Output Resolution
b09 b08 (mm s –1 )
0 1 1 u
y
wind (m s –1 ) = word 1 ∗ 0.001 ∗ 0.25 0.25
1 1 0 u
y
wind (m s –1 ) = word 1 ∗ 0.001 ∗ 0.50 0.50
2 0 1 u
y
wind (m s –1 ) = word 1 ∗ 0.001 ∗ 1.00 1.00
3 0 0 u
y
wind (m s –1 ) = word 1 ∗ 0.001 ∗ 2.00 2.00
TABLE B-5. Converting u
z
Wind from Word 2
Range Word 4 Range Code Conversion Output Resolution
b07 b06 (mm s –1 )
0 1 1 u
z
wind (m s –1 ) = word 2 ∗ 0.001 ∗ 0.25 0.25
1 1 0 u
z
wind (m s –1 ) = word 2 ∗ 0.001 ∗ 0.50 0.50
2 0 1 u
z
wind (m s –1 ) = word 2 ∗ 0.001 ∗ 1.00 1.00
3 0 0 u
z
wind (m s –1 ) = word 2 ∗ 0.001 ∗ 2.00 2.00
The speed of sound reported by the CSAT3 is the average between the three
sonic paths. The relationship to find the speed of sound is given in TABLE
B-6. Word 3 must be converted to a base 10 representation before applying the
equation.
B-4