Patent ID: 7869909

Claim:
A system for monitoring rail stress, comprising: (a) a length of rail, wherein the length of rail is subjected to biaxial strains under certain environmental conditions; (b) at least one sensing device adapted to detect, measure, and monitor rail stress, wherein the sensing device is mounted directly on the length of rail and further includes: (i) a flexible, generally flat shim, wherein the shim further includes a sensing region located thereon; (ii) at least one temperature sensor mounted within the sensing region on the shim; (iii) first and second strain sensors mounted within the sensing region on the shim, facing one another and defining a space therebetween, wherein the first and second sensors are oriented orthogonally to the biaxial strains experienced by the length of rail, wherein each strain sensor further includes first and second strain sensing elements set at right angles to one another, and wherein the four strain sensing elements in combination with one another form a Wheatstone bridge; (iv) a first plurality of solder pads mounted on the shim inside the space defined by the first and second strain sensors nearest the first strain sensor; (v) a second plurality of solder pads mounted on the shim inside the space defined by the first and second sensors nearest the second sensor; (vi) a plurality of lead wire attachment pads mounted between the first plurality of solder pads and the second plurality of solder pads; and (vii) a plurality of sensor wires connecting the solder pads to the lead wire attachment pads; and (c) at least one lead wire attached to the lead wire attachment pads, wherein the position of the lead wire attachment pads permits the lead wire to be attached to the center portion of the sensing device; (d) at least one data acquisition module in communication with the at least one sensing device, wherein the sensing device is enclosed within a sensor module, and wherein the sensor module further comprises a protective housing for enclosing the at least one sensing device and the at least one data acquisition module.