System for piston rod monitoring

A reciprocating system comprising:

• a piston comprising a first end and a second end opposite said first end;
• a piston rod coupled to said second end;
• a block, said piston rod extending at least partially through said block, wherein said piston rod is coupled via a crosshead assembly and a connecting rod to a crank shaft disposed in a crank case, and wherein said block is coupled to the crank case;
• and
• a sensor system for determining a condition associated with said piston rod, said sensor system comprising:
• an interrogator system comprising a first antenna, said first antenna coupled to an interior surface of said block;
• a second antenna separated from said first antenna by an air gap distance, said second antenna coupled to said piston rod, wherein said second antenna is a patch antenna, and wherein said second antenna is configured to communicate with said first antenna through a range of translational movement relative to said first antenna;
• and
• a surface acoustic wave sensor coupled to said second antenna and said piston rod, and configured to measure a strain associated with said piston rod and transmit, through said second antenna, data associated with the strain to said first antenna of said interrogator system.