Campbell Scientific CSAT3 CSAT3 3-D Sonic Anemometer - Page 60

Words 0 through 3

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Appendix B. Serial Communications with the CSAT3 TABLE B-2. RS-232 Output Word 0 b15 - b0 ux wind Word 1 b15 - b0 uy wind Word 2 b15 - b0 uz wind Word 3 b15 - b0 c b15 b14 b13 b12 diagnostic flags Word 4 b11 b10 b09 b08 ux range uy range b07 b06 uz range b05 - b00 counter B.3 Words 0 through 3 The ux, uy, and uz 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 ux Wind from Word 0 Range 0 1 2 3 Word 4 Range Code b11 b10 1 1 1 0 0 1 0 0 Conversion ux wind (m s-1) = word 0 ∗ 0.001 ∗ 0.25 ux wind (m s-1) = word 0 ∗ 0.001 ∗ 0.50 ux wind (m s-1) = word 0 ∗ 0.001 ∗ 1.00 ux wind (m s-1) = word 0 ∗ 0.001 ∗ 2.00 Output Resolution (mm s-1) 0.25 0.50 1.00 2.00 TABLE B-4. Converting uy Wind from Word 1 Range 0 1 2 3 Word 4 Range Code b09 b08 1 1 1 0 0 1 0 0 Conversion uy wind (m s-1) = word 1 ∗ 0.001 ∗ 0.25 uy wind (m s-1) = word 1 ∗ 0.001 ∗ 0.50 uy wind (m s-1) = word 1 ∗ 0.001 ∗ 1.00 uy wind (m s-1) = word 1 ∗ 0.001 ∗ 2.00 Output Resolution (mm s-1) 0.25 0.50 1.00 2.00 TABLE B-5. Converting uz Wind from Word 2 Range 0 1 2 3 Word 4 Range Code b07 b06 1 1 1 0 0 1 0 0 Conversion uz wind (m s-1) = word 2 ∗ 0.001 ∗ 0.25 uz wind (m s-1) = word 2 ∗ 0.001 ∗ 0.50 uz wind (m s-1) = word 2 ∗ 0.001 ∗ 1.00 uz wind (m s-1) = word 2 ∗ 0.001 ∗ 2.00 Output Resolution (mm s-1) 0.25 0.50 1.00 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

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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