Previous Page  7 / 59 Next Page
Show Menu
Previous Page 7 / 59 Next Page
Page Background

Ref. No. [UMCES] CBL 2016-015

ACT VS16-06


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.


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


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


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



3 Salinity Conditions: 0, 10, 34

Dissolved oxygen,(% air saturation): 0% (hypoxic), 20 – 30%, 100% and >120%, (levels were

achieved by mixing pure O


and N


sources with pure N


was used for the 0% O



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