Performance Verification Statement for the Sea-Bird Scientific HydroCAT Dissolved Oxygen Sensors

Sea-Bird Scientific 13431 NE 20

Street Bellevue Washington 98005 USA

09/23/2016

Sea-Bird Scientific comments on ACT Dissolved Oxygen Sensor Verification Statement

Sea-Bird Scientific would like to thank the ACT scientists, technicians, and staff that work to make these

evaluations possible. Below are comments in reference to specific elements of the testing protocols and

results that we feel warrant further explanation. You may contact Sea-Bird Scientific directly in you have

specific questions regarding this report. Please call Sea-Bird Scientific at 1-425-643-9866 and ask for

Dave Murphy, Director of Science.

1) We declined to participate in response time testing and profiling testing because the HydroCAT and

its sister instrument the MicroCAT are not intended for profiling and other fast response time

applications. They are intended for use at fixed sites and can be deployed unattended for long periods of

time in between site visits without a degradation in data quality.

2) Post deployment calibration verification conducted at Sea-Bird after each round of testing show that

the HydroCAT was well within its original calibration values and did not require servicing or calibration

before being redeployed in another round of testing.

3) The results from the testing in the Great Lakes show an “offset” from the reference sensor. Sea-Bird

optical dissolved oxygen sensors are calibrated individually in a temperature-controlled bath. Bath

temperatures are varied at each of 4 oxygen values the lowest calibrated temperature is 2°C. While this

provides a comprehensive 24-point calibration we do not optimize the calibration for performance in

low temperature range experienced in under ice deployments. In post deployment calibration

verification the sensor read .005 ml/l different from a reference sensor. The instrument was well within

its original calibrated values and did not require service or calibration before use in another round of

testing.

4) Unfortunately due to an error by ACT personnel the instrument was not set up correctly and logged

no data. The error was not discovered until the 120 day side by side testing was completed. We declined

a 30 day test as it would not have by conducted side by side the other test instruments and it would not

provide additional insight in to the instrument’s performance. We have multiple instruments deployed

off the coast of Hawaii by the Pacific Islands Ocean Observing System (PacIOOS). For real time and

historical data please see their website a

That testing showed that the optical dissolved oxygen

sensor was within the original accuracy specification (+/- 2%) after 21 months of continuous deployment

in the Puget Sound.

Sea-Bird recognizes the importance and value of 3rd party testing and evaluation and strongly supports

the ACT program. The ACT protocols test instruments with respect to basic operation and more

importantly how they work in the field. For long term monitoring programs the initial cost of an

instrument is quickly dwarfed by the operational and maintenance costs, particularly in remote and/or

high fouling environments. It is paramount to report good data for as long as possible and to minimize