US Patent 10480549 Cylinder operating condition monitoring device

A microcomputer of a detector that constitutes part of a monitoring device calculates differential pressures (first differential pressure, second differential pressure) between a first pressure value detected by a first pressure sensor provided in a first tube and a second pressure value detected by a second pressure sensor provided in a second tube, and on the basis of the calculated differential pressure, determines whether or not a reciprocating motion operation of the piston is in an intermediate state between a normal state and an abnormal state.