There are two conditions that can cause this issue with the Vernier Optical DO Probe. If you are measuring the rate of photosynthesis in the lab using an artificial light source, it could be light contamination. If you are doing a field experiment or...
Unlike many Vernier sensors that have collection units changed by selecting the desired unit from the Experiment menu in Logger Pro or by tapping on the live reading of the meter screen when using LabQuest, the Optical DO Probe has a switch on the ca...