What is a strain gauge and how does it work?

A strain gauge is a sensor that measures strain (deformation) based on the change in electrical resistance when stretched or compressed. When bonded to a surface, mechanical strain causes the gauge wire/foil to elongate or compress, changing its resistance proportionally. The gauge factor (GF = delta R/R divided by strain) typically ranges from 2-4 for metallic gauges. Strain gauges are fundamental to load cells, pressure transducers, and force sensors.