WHAT IS THE DIFFERENCE BETWEEN RELATIVE VIBRATION & ABSOLUTE VIBRATION REGARDING STEAM TURBINE???
For steam turbines, usually "relative vibration" means "shaft relative [us. against bearing shell] vibration" and "absolute vibration" concern bearing pedestal vibration against free space, measured by seismic transducer. By combination of signals measured in one common axis by shaft relative vibration transducer and bearing absolute vibration transducer, "shaft absolute vibration" can be calculated by electronic devices. In the past, "shaft absolute vibration" was measured directly by sensors with seismic system being in contact with rotating shaft surface.
