High Accuracy Bi-Circuit Wheel Load Sensor

A method of measuring wheel/rail loads comprising:

• providing a shear load sensing circuit (wide circuit) having at least two strain gauges spaced apart from one another by a predetermined longitudinal distance along the neutral axis of a rail in the span between two ties;
• providing a shear load sensing circuit (narrow circuit) having at least two strain gauges spaced apart from one another by a smaller predetermined longitudinal distance along the neutral axis of the rail in the span between two ties, wherein the strain gauges of the narrow circuit are located between the strain gauges of the wide circuit;
• calibrating the responses of the wide circuit and narrow circuit by applying known loads at predetermined points along the span to generate sensitivity curves for the wide circuit and narrow circuit as a function of the location of the known load along the span;
• calculating a ratio curve based on the ratio of the sensitivity curves for the wide circuit and narrow circuit;
• and
• determining the location and magnitude of an unknown load on the rail by:
• (a) determining the location of the unknown load along the span based on the ratio curve;
• and
• (b) determining the magnitude of the unknown load based on a sensitivity curve and the location of the load along the span.

A method of measuring wheel/rail loads comprising:

• providing a shear load sensing circuit (wide circuit) having at least two pairs of strain gauges on opposite sides of the rail spaced apart from one another by a predetermined longitudinal distance along the neutral axis of a rail in the span between two ties, said strain gauges arranged in a bridge configuration;
• providing a shear load sensing circuit (narrow circuit) having at least two pairs of strain gauges on opposite sides of the rail spaced apart from one another by a smaller predetermined longitudinal distance along the neutral axis of the rail in the span between two ties, wherein the strain gauges of the narrow circuit are located between the strain gauges of the wide circuit;
• calibrating the responses of the wide circuit and narrow circuit by applying known loads at predetermined points along the span to generate sensitivity curves for the wide circuit and narrow circuit as a function of the location of the known load along the span;
• calculating a ratio curve based on the ratio of the sensitivity curve for the wide circuit divided by sensitivity curve of the narrow circuit;
• and
• determining the location and magnitude of an unknown load on the rail by:
• (a) determining the location of the unknown load along the span based on the ratio curve;
• and
• (b) determining the magnitude of the unknown load based on the sensitivity curve of the wide circuit and the location of the load along the span.