Performance Verification Statement for the Hach Hydrolab DS5X and HL4 Dissolved Oxygen Sensors

26 / 59

Ref. No. [UMCES] CBL 2016-014
ACT VS16-05
26
Figure K. Long-term stability and thermal stress challenge of the Hach HL4 LDO (sn 0431).
Instrument was maintained in well circulated tank and oxygen content manipulated by alternately
varying water temperature set point between 15 and 25 oC several times per week of deployment.
Top Panel: Time series of the instrument readings at 15 min intervals with discrete values for
Winkler assay of grab samples taken at sensor level. Bottom Panel: Offset in paired DO readings
of and Winkler grab samples. The HL4 sonde failed on the 7th day of the deployment.