The patented C-Guard "smart" module is designed to provide mechanical condition and compressor performance monitoring for critical compressor applications. The module (one per cylinder) accepts inputs from seven primary sensors, including head and crank end pressure, suction and discharge temperature, and cross head vibration plus a crankshaft speed/phase reference and two auxiliary channels for rod drop/runout, cylinder vibration, or additional temperature inputs. All inputs are monitored continuously and the internal processor calculates compressor IHP, rod loads, percent of rod reversal, volumetric efficiencies, capacity, clearances, theoretical discharge temperature, and other critical performance and condition monitoring calculations.