describe the structure of a metal wire strain gauge
Strain gauge A typical strain gauge arranges a long, thin conductive strip in a zig-zag pattern of parallel lines. This does not increase the sensitivity, since the percentage change in resistance for a given strain for the entire zig-zag is the same as for any single trace. However, a single linear trace would have to be extremely thin and hence liable to overheating (which would both change its resistance and cause it to expand), or would have to be operated at a much lower voltage, making it harder to measure resistance changes accurately.