1. A system configured to monitor a plurality of analog-to-digital converters, comprising: a plurality of input channels, each in communication with a different phase of a three-phase electric power delivery system, and configured to receive a plurality of analog signals from the three phases; a composite signal subsystem configured to generate a composite signal based on the plurality of input channels; an analog-to-digital converter subsystem in communication with the plurality of input channels and the composite signal subsystem, the analog-to-digital converter subsystem configured to produce a digitized representation of each of the plurality of input channels and a first digitized representation of the composite signal; and a monitor subsystem in communication with the analog-to-digital converter subsystem and configured to identify at least one error in the digitized representation of at least one of the plurality of input channels produced by the analog-to-digital converter subsystem and based on the digitized representation of the composite signal and the digitized representations of the plurality of input channels.