Hanna Instruments portable meter for dissolved oxygen with an optical sensor instead of a membrane electrode, one model.
HI98198
This Hanna Instruments portable meter measures dissolved oxygen with an optical sensor instead of a membrane electrode.
A membrane DO probe consumes oxygen to measure it, so it needs flow, it drifts as the membrane fouls, and its electrolyte has to be changed. An optical sensor measures by luminescence quenching: nothing is consumed, there is no membrane and no electrolyte, and it holds calibration for far longer.
An electrochemical meter is three things that fail separately: the electrode, which ages and eventually dies; the meter, which rarely goes wrong; and the calibration, which is only as recent as the last time somebody did it. Almost every bad reading traces to the first or the third.
Budget for electrodes as consumables, store them wet in storage solution rather than water, and calibrate against fresh buffers at the temperature you will measure at.
The optical cap is the consumable and is replaced on a schedule rather than when it fails; budget for it as part of the instrument.
Supplied as one model.