Vibratory-wire pressure sensor

Claim 1

A force-sensor of the vibrating-wire type for use in a process instrumentation system for developing a measurement signal corresponding accurately to an applied force within a predetermined operating range; said sensor comprising: wire-supporting means including first and second means adapted to tightly grip the ends of a wire; a wire held tautly between said first and second means; pressure-responsive means coupled to said first and second means to apply thereto a force tending to move said first and second means apart so as to apply a tension to the wire; said wire being in the form of a substantially flat ribbon having a thickness of about 0.001 inches, and an aspect ratio of at least 10:1; wire-excitation means to produce vibrations of said wire in the primary mode; and bias tension spring means permanently coupled to said wire-supporting means and continuously operable at all times during measurement operation of the instrument to elevate the tension applied to said wire by said pressure-responsive means so as to operate the wire within a tension range which is substantially offset from zero, whereby said wire tension during measurement operation of the instrument never approaches a tension near zero and so that the natural frequency of oscillation at zero tension is not a factor in the functioning of the instrument.