A sampling module, for sampling one or more analog characteristics of a power transmission system, including at least one input circuit for sampling a respective analog characteristic. Each input circuit includes: a scaling circuit for reducing the magnitude of the analog characteristic to a desired level; an isolating circuit for creating an electrical barrier between respective upstream and downstream portions of the input circuit; and an analog to digital converter for digitizing the analog characteristic to produce a digital data stream. The scaling circuit is electrically connected to an input of the analog to digital converter, and the isolating circuit is electrically connected directly to an output thereof.