No, because the impedance meter is completely galvanically disconnected from the electrodes and the EEG amplifier when it is turned off. So , turn the impedance meter function on while you are placing the electordes and watch how you are doing. When you are done and want to start the neurfeedback session, turn it off. You can re-check the impedances at any time, but during that time, you will not measure EEG signals.