JFE Advantech ARO-FT, User Manual

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35
Oxygen calculation and compensation 9.5
The calibration for this instrument uses traceable reference gases according to the Japanese national standard.
The calibration coefficients (
𝑐𝑐
0
− 𝑐𝑐
2
,
𝑑𝑑
0
− 𝑑𝑑
4
, and
𝑒𝑒
0
) are derived from 16 calibration points (4 temperature
points and 4 oxygen concentrations). The oxygen concentration ( 𝐷𝐷𝐷𝐷
)
is calculated from the equation below:
𝐷𝐷𝐷𝐷 = ��
1 + 𝑑𝑑
0
∙ 𝑇𝑇
𝑑𝑑
1
+ 𝑑𝑑
2
∙ 𝑁𝑁 + 𝑑𝑑
3
∙ 𝑡𝑡 + 𝑑𝑑
4
∙ 𝑡𝑡 ∙ 𝑁𝑁�
𝑒𝑒
0
− 1 � ∙
1
𝑐𝑐
0
+ 𝑐𝑐
1
∙ 𝑇𝑇 + 𝑐𝑐
2
∙ 𝑇𝑇 2
Uchida et al. (2010)
𝐷𝐷𝐷𝐷
: Dissolved Oxygen [ μmol L
-1
]
𝑐𝑐
0
− 𝑐𝑐
2
, 𝑑𝑑
0
− 𝑑𝑑
4
, 𝑒𝑒
0
: Calibration coefficients
𝑇𝑇
:
Temperature [ ° C]
𝑁𝑁
: (AD value of DO) / 10000
𝑡𝑡 : LED accumulated time
The pressure-compensated oxygen concentration ( 𝐷𝐷𝐷𝐷
pc
) is calculated from the equation below:
𝐷𝐷𝐷𝐷
pc
= 𝐷𝐷𝐷𝐷 � 1 + 𝐶𝐶
𝑝𝑝
𝑝𝑝 �
𝑝𝑝
:
Pressure [MPa]
𝐶𝐶
𝑝𝑝
: Calibration coefficient
The salinity-compensated oxygen concentration (
𝐷𝐷𝐷𝐷
sc
) is calculated by multiplying the factor of the effect of
salt on the oxygen solubility (Benson and Krause 1984, García and Gordon 1992). The salinity &
pressure-compensated oxygen concentration can be calculated by using
𝐷𝐷𝐷𝐷
pc
in the following equation:
𝐷𝐷𝐷𝐷
sc
= 𝐷𝐷𝐷𝐷 exp � 𝑆𝑆 � 𝐵𝐵
0
+ 𝐵𝐵
1
𝑇𝑇
𝑠𝑠
+ 𝐵𝐵
2
𝑇𝑇
𝑠𝑠
2
+ 𝐵𝐵
3
𝑇𝑇
𝑠𝑠
3
� + 𝐶𝐶
0
𝑆𝑆
2
�
𝑇𝑇
𝑠𝑠
= ln �
298.15 − 𝑇𝑇
273.15 + 𝑇𝑇�
𝑇𝑇
: Temperature [ ° C]
𝑆𝑆
: Salinity [‰ or PSU]
The oxygen concentration in volumetric units ( μmol L
-1
) can be converted to gravimetric units ( μmol kg
-1
) by
dividing by the potential density calculated from the CTD data.
𝐵𝐵
0
= - 6.24523 × 10
-3
𝐵𝐵
1
= - 7.37614 × 10
-3
𝐵𝐵
2
= - 1.03410 × 10
-2
𝐵𝐵
3
= - 8.17083 × 10
-3
𝐶𝐶
0
= - 4.88682 × 10
-7