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Ref. No. [UMCES] CBL 2016-013
ACT VS16-04
5
with corresponding DO concentrations of 8.6 and 12.6 mg/L, respectively. Two profiling trials
were conducted at each location. The first trial involved equilibrating test instruments at the
surface (3m) for ten minutes and then collecting three Niskin bottle samples at one minute
intervals. Following the third sample, the rosette was quickly profiled into the hypolimnion where
samples were collected immediately upon arrival and then each minute for the next 6 minutes. The
second trial was performed in the reverse direction. For Muskegon Lake, the range in
measurement differences between instrument and reference was -0.15 to 1.78 mg/L for cast 2 and -
0.92 to -0.17 mg/L for cast 3 (cast 1 was aborted and redone as cast 3. For Lake Michigan, the
range in measurement differences was -3.03 to 0.40 mg/L for cast 1 and -0.81 to 3.05 mg/L for cast
2. The equilibration rate of the sensor differed across each of the profiles with no obvious trend
across temperature or DO levels.
BACKGROUND AND OBJECTIVES
Instrument performance verification is necessary so that effective existing technologies can
be recognized and so that promising new technologies can be made available to support coastal
science, resource management and ocean observing systems. To this end, the NOAA-funded
Alliance for Coastal Technologies (ACT) serves as an unbiased, third party testbed for evaluating
sensors and sensor platforms for use in coastal environments. ACT also serves as a comprehensive
data and information clearinghouse on coastal technologies and a forum for capacity building
through workshops on specific technology topics (visit
www.act-us.info).
As part of our service to the coastal community, ACT conducted a performance verification
of commercially available, in situ dissolved oxygen (DO) sensors through the evaluation of
objective and quality assured data. The goal of ACT’s evaluation program is to provide technology
users with an independent and credible assessment of instrument performance in a variety of
environments and applications. To this end, the data and information on performance
characteristics were focused on the types of information users most need.
The fundamental objectives of this Performance Verification were to: (1) highlight the
potential capabilities of particular in situ DO sensors by demonstrating their utility in a range of
coastal environments; (2) verify the claims of manufacturers on the performance characteristics of
commercially available DO sensors when tested in a controlled laboratory setting, and (3) verify
performance characteristics of commercially available DO sensors when applied in real world
applications in a diverse range of coastal environments.
INSTRUMENT TECHNOLOGY TESTED
Onset’s HOBO U26 Dissolved Oxygen Logger uses the RDO® Basic Technology
developed by In-Situ, Inc. This technology represents the latest advancements in optical Dissolved
Oxygen (DO) measurement. By improving upon the breakthrough optical DO sensor technology
that In-Situ brought to the environmental market in early 2004, the RDO Basic sensor provides
higher quality data and more robust performance than traditional methods. The “Basic” version of
the RDO used in the HOBO U26 provides the RDO advantages in an affordably-priced stand-alone
data logger.
Optical sensor technology uses LED lights, a lumiphore and a detector. A source of light
excites a lumiphore which luminesces, emitting a light of a different wavelength. Typically,