[mkbh10]

How do I measure open circuit voltage of a 3 electrode electrochemical cell connected to a potentiostat ?

[DevaDevil]

very simple:

connect electrodes to potentiostat, tell it to measure potential.
Insert electrodes, do not turn on potential control of your cell and read out what the potential is between working and reference electrode.


Alternately, you can also skip the potentiostat; insert the electrodes, shortcut the working with counter and put a volt meter between working and reference electrode.