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Ref. No. [UMCES] CBL 2016-010
ACT VS16-01
13
RESULTS of LABORATORY TESTING
Instrument accuracy for the JFE Rinko AroUSB and AroW-USB were tested under nine
combinations of temperature and salinity over a range of DO concentrations from 10% to 120% of
saturation (Table 1). Results are plotted as a time series of instrument readings against the time series
of comparative Winkler reference samples (Figures A-I for AroUSB; M-U for AroW-USB). The
bottom panel of each figure shows the time series of the difference in instrument measurement versus
corresponding reference sample. Plotted differences were limited to a range of ± 2.0 mg/L, as values
exceeding this range are well outside any expected performance specification and likely occurred as a
result of bubbles from the sparging gas used to vary dissolved oxygen concentrations getting trapped
on the sensor foil. Comparisons of tank duplicates taken at opposite sides of the tank from between 9-
18 of the timepoints during each trial showed a mean difference of 0.017 mg/L, with a range over the
nine trials of 0.006 – 0.038 mg/L. Those values are within the analytical precision of the reference
method and indicate conditions throughout the tank were very homogeneous and trapping of bubbles
on the sensor foil happened as isolated events, which were clearly distinguishable. However, small
changes in measured DO concentrations did occur during some of the sampling phases indicating the
tank was slightly moderating after sparging was stopped. Those small drifts in DO concentrations
were clearly captured by both instrument and reference sample measurements.
Table 1.
Dissolved oxygen temperature and salinity challenge trial conditions. For each trial pre and post
measurements of tank temperature (
o
C) and salinity (S) were made with a calibrated SBE26+4M CTD,
equilibrated in well mixed tank for 20 min until stable readings obtained.
Trial ID
Mean
Temp
o
C
S.D.
Temp
o
C
Mean
Salinity
PSU
S.D.
Salinity
PSU
Levels of
DO Tested
mg/L
Figure for
AroUSB
Figure for
AroW-USB
L_T15_S00 15.44
0.03
0.00
0.000
0, 2, 5,9,10,14
A
M
L_T15_S10 15.47
0.01
8.82
0.003
0, 2, 8, 9, 13
B
N
L_T15_S35 15.39
0.03
34.20
0.009
0,2,6,8,12
C
O
L_T04_S00 5.40
0.08
0.00
0.000
0,4, 12, 17
D
P
L_T04_S10 5.30
0.03
8.98
0.009
0, 5, 12, 16
E
Q
L_T04_S35 5.23
0.07
34.77
0.073
0, 4, 10, 14
F
R
L_T30_S00 30.22
0.03
0.00
0.000
0, 3, 5, 9
G
S
L_T30_S10 30.51
0.12
9.28
0.036
0, 3, 7, 10
H
T
L_T30_S35 30.61
0.07
34.43
0.050
0, 2, 6, 9
I
U
The mean and standard deviation of the differences between instrument and reference
measurements for each trial (n= 24 - 42) are presented in Table 2 for both the AroUSB and the AroW-
USB. Mean difference among trials for the AroUSB ranged from -0.277 to 0.265 mg/L DO, and
between -0.277 to 0.134 mg/L DO for the AroW-USB. All instrument DO readings were post
processed using the manufacturer’s software to correct for salinity and there were no obvious patterns
to the level of accuracy over the full range of salinity and temperature tested for either model.