EXTENDED RANGE VIBRATING WIRE STRAIN MONITOR

摘要

The invention relates to the field of measuring instruments and, in particular to sensing apparatus capable of measuring displacement or deformation for the ultimate purpose of monitoring strain and/or stress. The vibrating wire measuring principle provides a very reliable method of measuring small deformations with high precision. Measurement apparatus utilizing this principle, however, tend to be limited in range to the elastic limit of the stretched wire. To increase the useful range of measurement of a vibrating wire monitor, a spring may be placed in series with the wire. In order to prevent the spring from vibrating during the resonancing of the wire and thereby delaying the determination of the wire's resonant frequency, the invention contemplates isolation of the spring from the wire in a vibrational sense. In one form of the invention, isolation is achieved by causing a nodal point to be formed on the spring side of the wire. The nodal point may be formed by pressing a fret against the wire.