I'm trying to make a bioanode for use in a microbial fuel cell. I have a piece of carbon cloth in an acetate solution with river sediment. I'd like to know the potential of the anode, so I connected it to an Ag/AgCl reference electrode also in the sediment/acetate solution (note that ref electrode has 3M KCl, about 0.2V relative to SHE). Between the reference electrode and anode, I have a multimeter connected with the positive going to the Ag/AgCl reference electrode and negative going to the carbon cloth anode.
The multimeter reads +0.2V. Does this mean my anode potential is 0.4V (0.2V from multimeter reading + 0.2V for reference electrode correction)? OR, does this mean that my anode potential is 0V (-0.2V multimeter reading + 0.2V for reference electrode correction). I'm not clear if the positive side of the multimeter and negative side are connected correctly to the electrodes. If they are connected incorrectly, then the voltage sign should be flipped.