An apparatus comprises a headset and a control unit in communication with each other. The headset comprises a plurality of electrodes operable to measure ERP readings. The headset is configured to be positioned on a test subject. The control unit is configured to store and administer an ERP test protocol. The control unit is also configured to administer an impedance test and process the impedance of the electrodes. The impedance testing may be performed in an in-band fashion, along the same channels used to perform the ERP testing, at the same frequency of the ERP readings, and substantially simultaneously with the ERP readings.
