Mario Fasching

See Gain for usages of the word related to different channels of the O2k.

The gain of the oxygen sensors can be adjusted by the user selecting “Oxygraph” / “O2k Control” from the venue. The gain has to be adjusted to the oxygen level in your experiment. When the gain setting is to high for your experiment the signal will reach a constant maximum value and the flux will therefore apparently drop to zero. A good gain for experiment at or near air saturation is a gain of 2. This is now the default setting when DatLab is shipped. In prior versions of DatLab the default gain was set to 4. This was to high to be used at air saturation for some laboratories situated at or near seal level. Therefore for all experiments at air saturation a gain of 2 should be used to avoid reaching the maximum value during an experiment. Each gain requires a separate calibration of the oxygen signal. Therefore after changing the gain you should not only perform a calibration at air saturation (as always before an experiment), but also a new zero calibration, see also Air calibration for high O2 experiments. If your frequently switch between gains, the easiest way is to have a DatLab file for zero calibration at gain = 0 and one for zero calibration at gain = 2. Then, whenever you change gain you just use the "read from file" function in the calibration window. But you also could insert the values manually. Oxygen signals that have been obtained after proper calibration are independent of the gain setting. Therefore oxygen concentrations (and fluxes) that have been recorded at different gain settings can of course be used together.