Sea-Bird Electronics SBE 19plusV2 - Page 244

6
Create a table with average pressure, temperature, salinity, oxygen saturation, and SBE 43 output voltage for each
water sampler closure depth, by importing the .btl file into a spreadsheet. Then, enter by hand the Winkler titration
dissolved oxygen values from your titration log, matching water sampler closures to pressures.
Calculate
()
)
*
(
32
****0.1),(
K
PE
eTCTBTASTOxsol +++∗= φ ,
using A, B, C, and E from the SBE 43 calibration sheet.
Then, calculate Winkler O
2
/
φ
.
An example table is shown below (using A = -0.00034959, B = 0.00013078, C = -0.0000027243, and E = 0.0.036),
with
φ
(phi) in column 7 and Winkler O
2
/
φ
(Winkler/phi) in column 8.
Table 1. Example calculation of phi and Winkler/phi.
Pressure
(db)
Temperature
(°C)
Salinity
(PSU)
Oxygen
Solubility
(ml/l)
SBE 43
Voltage
Output (V)
Winkler
Oxygen
(ml/l)
phi Winkler/phi
194.6 15.43 35.617 5.623 2.452 5.172 5.852 0.884
169.5 16.26 35.713 5.529 2.540 5.306 5.744 0.924
143.7 17.17 35.793 5.430 2.635 5.488 5.632 0.974
93.9 18.97 35.881 5.247 2.753 5.545 5.424 1.022
48.7 23.38 36.087 4.841 2.697 4.966 5.009 0.992
24.0 23.94 35.840 4.801 2.664 4.852 4.956 0.979
9.6 23.95 35.839 4.800 2.667 4.851 4.946 0.981
Perform a linear regression, with:
• Winkler O
2
/
φ
(shown as Winkler/phi in the table) as the Y data
• SBE 43 output voltages as the X data
If a spreadsheet or statistical calculator is not available, the regression equations are:
()
∑∑
∑∑∑
−∗
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
∗−
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
∗∗
=
2
2
22
VVn
OWinkler
V
OWinkler
Vn
M
φφ
n
VM
OWinkler
B
∑∑
∗−
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
φ
2
Where:
n = number of data pairs
M = Slope
B = Offset
And:
Soc = M
Voffset = B/M
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