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Ref. No. [UMCES] CBL 2016-015
ACT VS16-06
7
ODO % EU = ODO % Sat reading corrected with live barometric reading (available only on
EXO2 Handheld). Fixes the % Sat output to 100%, and conforms
to British and
EU standards.
PERFORMANCE EVALUTION TEST PLAN
Laboratory Tests
Laboratory tests of accuracy, precision, response time, and stability were conducted at
Moss Landing Marine Lab. All tests were run under ambient pressure (logged hourly from a
barometer at the laboratory) and involved the comparison of dissolved oxygen concentration
reported by the instrument versus Winkler titration values of water samples taken from the test
baths. All tests were run in thermally controlled tanks at specific temperature, salinity, and DO
concentrations. Tanks were well mixed with four submersible Aquatic Ecosystem Model 5 pumps
with flow rates of 25 L/min. Temperatures were controlled to within approximately 0.2
o
C of set
point using Thermo Digital One Neslab RTE 17 circulating thermostats flowing through closed
coils distributed within the tank. Four RBR temperature loggers were deployed within the tank to
verify actual temperature to better than 0.02
o
C. Salinity was varied by addition of commercial
salts (Instant Ocean) to Type 1 deionized water. Salinity was verified at the beginning and end of
each test condition by analysis on a calibrated CTD
.
Dissolved oxygen concentrations were
controlled by use of compressed gases of known oxygen concentration sparging through diffusers
within the tank. Tanks were covered with a layer of floating closed-cell plastic insulation that
continuously sealed the water surface and to minimize atmospheric exchange. If required by the
manufacturer, instruments were only calibrated prior to the start of the first lab test, and then again
prior to the stability test which began one month later. The following series of tests were
conducted in the laboratory trials:
Accuracy at various T/S and DO conditions
A series of measurements were conducted under 36 discrete conditions to target 3
temperatures, 3 salinities, and at least 4 DO concentrations as follows:
•
Temperature Conditions: 5, 15, 30
o
C
•
3 Salinity Conditions: 0, 10, 34
•
Dissolved oxygen,(% air saturation): 0% (hypoxic), 20 – 30%, 100% and >120%, (levels were
achieved by mixing pure O
2
and N
2
sources with pure N
2
was used for the 0% O
2
concentration)
Tests were run such that all 4-6 DO concentrations were tested for a fixed temperature and
salinity on the same day.
The tests began at ambient, near air saturation, conditions following
overnight equilibration of tank water to the test salinity and temperature. Subsequently DO were
dropped to near 0 mg/L and increased stepwise to the highest concentration
. Instruments were
allowed to equilibrate at the fixed temperature and salinity for 1 h before the start of that day’s
trial. Sparging with each DO gas concentration was conducted for a minimum of 60 minutes prior
to the start of data collection and reference sampling. For each test condition, the test instruments
were programmed to sample at no slower than 1 minute intervals and reference samples were
collected at 6 timepoints spaced 5 minutes apart for each of the fixed conditions. For three of the
timepoints duplicate samples were collected from two different sampling ports mounted at opposite
ends of the tank to access heterogeneity within the tank. Inlets of sampling ports were positioned