Embedded resistive strain sensors for harsh environments

Strain gages developed using high-definition direct write technology enable direct bonding to substrates without an adhesive layer, so greater shear forces may be faithfully transmitted and thicker, more robust conductors may be used for strain-sensing. Effects of hysteresis, creep, and temperature limitations common to adhesively-bonded gages can also be mitigated. Manufacture and installation of the gage (and lead wires) are automatic and simultaneous, reducing preparation time and cost. Using the above developed method, industrial-grade strain gages have been fabricated and tested. Standard gage resistances between 120/spl Omega/-350/spl Omega/ have been achieved on grids smaller than 10mm/sup 2/ using nickel-chrome as the gage material. Thermal plasma-sprayed laser-cut resistive gages have achieved gage factors of 1.3, operating linearly and repeatably for more than 10/sup 5/ cycles between /spl plusmn/1000/spl mu//spl epsiv/. Additional performance metrics, e.g. temperature sensitivity and compensation, were treated in this paper.