Effective 6-Month Deployment in Marine Waters

EXO2 sonde and Seaguard instrument

EXO2 and AADI SeaGuard, before and after 180-day deployment in Koljoe Fjord

The EXO2 water quality sonde was deployed alongside an Aanderaa Seaguard instrument under the cold saltwater of the Koljoe Fjord in Sweden. Water temperatures from October to May ranged from 0 to 12ºC (32 to 54ºF).

The EXO2 sonde recorded data every hour for 180 days, and was equipped with the following sensors: optical dissolved oxygen, conductivity-temperature, depth, pH/ORP, total algae (chlorophyll and blue-green algae combined), and fDOM.




EXO2 sensors and anti-fouling wiper

EXO2 sensors free from biofouling after 180-day deployment. (The anode is positioned approximately in the four o'clock position on the sonde.)

Upon recovery after 180 days, the EXO2 sensor tips were extremely clean of any biofouling. The key to the sensors’ cleanliness is the robust central wiper on the EXO2 that brushes away biofouling, dirt and particles prior to each sensor reading, thus assisting in accurate data collection each time.

Additionally, a sacrificial anode was installed in one of the sensor ports to counteract the effects of corrosive media, particularly saltwater or brackish estuarine water. The EXO replaceable zinc anode is placed in electrical contact with metals that are susceptible to corrosion and the zinc is preferentially oxidized (or corroded), thus preventing damage to the metal components on EXO’s bulkhead, probe housings, and copper antifouling guard.




EXO sacrificial zinc anode

EXO sacrificial zinc anode, before and after 180-day deployment

180 days is the longest unattended, autonomous deployment of an EXO sonde to date, and this deployment is a great example of the effectiveness of EXO for marine and coastal applications.

Given the cleanliness of the sensors and the remaining battery life, the EXO sonde could have deployed for an even longer period of time.



Photos courtesy of Anders Tengberg, Aanderaa Data Instruments AS.




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