Apparatus and method for measuring electrode impedance during electrophysiological measurements

The present disclosure is related to methods, systems and apparatus for performing electrophysiological measurements utilizing three or more electrodes attached to a patient. The system in various embodiments may include three or more electrodes attached to the patient and at least one analog-to-digital converter with external circuitry electrically coupled to the electrodes. The system may further include a microprocessor for driving the analog-to-digital conversion process, various inputs and variable frequency current outputs electrically coupled to the microprocessor for receiving signals from the electrodes and sending driven current signals to the electrodes.