LINK Systems System 1100 Tonnage Monitor - Manual (Page 43)

THEORY OF OPERATION
___________________________________________________________________
3-6
Figure 8. Harmonic Noise.
transducers when no load forces are being developed in the machine,
and may cause a small variation in displayed tonnage from stroke to
stroke for each channel as harmonic strain is added to load strain.
It should be noted, however, that the effects of harmonic vibration
are generally reduced when the machine actually exerts force in the
production process. Figure 7 illustrates harmonic "mechanical
noise" in a strip chart recording of a tonnage monitor output
signal.
3.4.2 Structural "Ringing"
Any elastic body has a natural response which dies out with time if
energy is suddenly applied to or removed from the body. Just as
a diving board vibrates back and forth in dying oscillations until
it is again stationary when suddenly relieved of a person's weight,
a machine structure "rings" when load is suddenly released by
material breakthrough in blanking and piercing operations. Figure
8 illustrates a typical ringing at the end of a blanking operation
in a tonnage monitor signal.