TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017
page 18 of 93
If the salinity varies significantly, you should simultaneously measure the salinity externally and perform a
more accurate correction by a post compensation of the data. An Excel spreadsheet containing the
equations for post compensation of the measurements is available for download at the document
download site at the Aanderaa Global Library, refer
www.aanderaa.com
.
If the
Salinity
property in the sensor is set to zero, the compensated O
2
concentration, O
2c
in
µM
, is
calculated from the following equation:
[ ]
(
)
2
0
3
3
2
2
1
0
2
2
S
C
T
B
T
B
T
B
B
S
C
S
S
S
e
O
O
+
+
+
+
⋅
=
where:
O
2
is the measured O
2
concentration
S
= measured salinity in ppt or PSU
T
s
= scaled temperature
+
−
=
t
t
15
.
273
15
.
298
ln
t
= temperature,
°C
B
0
=
-6.24097e-3
C
0
=
-3.11680e-7
B
1
=
-6.93498e-3
B
2
=
-6.90358e-3
B
3
=
-4.29155e-3
If the
Salinity
property in the optode is set to other than zero (zero is the default value), the equation
becomes:
[ ]
(
)
)
(
)
(
2
2
2
0
2
0
3
3
2
2
1
0
0
S
S
C
T
B
T
B
T
B
B
S
S
C
S
S
S
e
O
O
−
+
+
+
+
−
⋅
=
Where S
0
is the
internal salinity setting.
2.4 Depth Compensation of Data
The response of the sensing foil decreases to some extent with the ambient water pressure (3.2% lower
response per 1000 m of water depth or dbar –investigated in detail by Uchida et al., 2008, for full
reference see publication list in appendix 11). This effect is the same for all AADI oxygen Optodes and is
totally and instantly reversible and easy to compensate for.
The depth compensated O
2
concentration,
O
2c
, is calculated from the following equation:
⋅
+
⋅
=
1000
032
.
0
1
2
2
d
O
O
c
where:
d
is depth in meters or pressure in dbar.
O
2
is the measured O
2
concentration in either
µ
M or %.
The unit of the compensated O
2
concentration,
O
2c
,
depends on the unit of the
O
2
input
NOTE! Depth compensation is not performed within the Optode
.
Examples of depth compensation:
