A system and associated method is disclosed for determining whether signal is valid. The system comprises an electrode apparatus comprising a plurality of electrodes configured to be located proximate tissue of a patient. A display apparatus comprising a graphical user interface, wherein the graphical user interface is configured to present information to a user. A computing apparatus coupled to the electrode apparatus and display apparatus, wherein the computing apparatus is configured to determine whether a signal acquired from a channel associated with an electrode from the plurality of electrodes is valid and sufficiently strong by i) calculating a first derivative of the signal； ii) determining a minimum and maximum derivative from the first derivative； iii) determining whether signs of the minimum and maximum derivative are different； and in response to determining whether the signs of the minimum and maximum derivative are different, displaying on a display apparatus whether the signal is valid.
