The HOBO U26 Dissolved Oxygen logger has been part of a multi-year evaluation of DO loggers and sensors by the Alliance for Coastal Technologies (ACT), and the results have just been published online. This provides an un-biased report of how our U26 performs in lab and field conditions.
… and here is a link to to get to reports on the six other loggers/sensors that were tested:
http://www.act-us.info/evaluations.php (click on the link for “Dissolved Oxygen II” to skip down to the links to the other reports.)
The U26 logger did very well in these tests. The lab tests showed the U26 to be very accurate over a wide range of DO, temperature, and salinity conditions tested. Only two of the sensors tested were more accurate than the U26: the In-Situ RDO sensor, which ours is based on, and the Seabird (which is a very high-end oceanographic system). Our U26 was more accurate than the others (from PME, YSI, JFET and Hach.) The U26 also performed well in the long-term (56 days) lab test and maintained its accuracy over this period, similar to or better than the others.
The field tests confirmed the importance of keeping the sensor clean in high-fouling environments. Several of the DO sensors in the test have wipers to clean the fouling off, which allows them to go longer without having to be serviced. With the U26 you need to clean the fouling off on a regular basis before it degrades performance. For the brackish site (in Chesapeake Bay) the U26 measurements were significantly degraded after 20 days, while in the saltwater site (in Hawaii), measurements degraded after 50 days. We would recommend cleaning the sensors before the fouling reaches these points.
The U26 operated reliably throughout these challenging tests, as compared to three of the other loggers which stopped working at some point during the tests.