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.