Hanna Instruments portable meter for dissolved oxygen, one model.
HI98193
This Hanna Instruments portable meter measures dissolved oxygen, with the BOD calculation built in.
Biochemical oxygen demand is not measured directly: it is the difference between the oxygen in a sample now and after five days of incubation. A meter that does the arithmetic and holds the initial reading removes the step where the number usually gets lost.
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 five-day incubation temperature matters as much as the readings; a BOD result from an uncontrolled incubator is not comparable to anyone else's.
Supplied as one model.