A new technique for measuring strain with extremely high resolution was developed. This technique relies on the ultrasensitive (high coupling factor) amorphous ribbons prepared by magnetic field annealing.Here certain ribbons (e.g., Metglas 2605SC, 2605Shyphen;2) when annealed in a transverse field achieve magnetomechanical coupling factorsk33ape;0.95.1In this technique the sensitive ribbon is bonded in place on an aluminum bending member with ahighlyviscous liquid (eegr;ape;107cP at 298 K). This procedure allows the ribbon to remain in a stresshyphen;free environment following an initial relaxation period of approximately 10 min. In this state the ribbon is in a lsquo;lsquo;blockedrsquo;rsquo; (constant strain) condition while at the same time being stresshyphen;free. Since the susceptibility of the ribbon is highly strain dependent, a measurement of the susceptibility is a direct measurement of the strain. We define a figure of merit (FM) as (part;khgr;/part;egr;)/khgr; in analogy with (part;R/part;egr;)/Rfor a conventional strain gage. Values of FM of about 2times;105were obtained. This is three orders of magnitude better than semiconductor strain gages. The main features of this technique are its large dynamic range, high sensitivity and strain resolution, very small temperature dependence, and broad frequency range. In a simple device, we measured strains as low as 3times;10minus;10and secured a dynamic range of 104. The potential dynamic range exceeds 105. Measurements of FM and dynamic range were made from 0.01 to 1 Hz. We expect no deterioration in operational characteristics far above 1 Hz. Calculations also indicate only a slight temperature dependence of the FM from 0 to 500 K.
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