Which sensor uses strain-induced resistance change to measure a physical quantity?

Which sensor uses strain-induced resistance change to measure a physical quantity?

• A. Thermocouple
• B. RTD
• C. Strain gauge
• D. Capacitive sensor

Answer: (C)

The key idea is converting mechanical deformation into a change in electrical resistance. A strain gauge is designed for this. It uses a thin metallic foil or wire whose length and cross‑section change when the structure it’s bonded to is stretched or compressed. That change in geometry alters the resistance, with the fractional change ΔR/R proportional to the strain ε (ΔR/R ≈ GF × ε, where GF is the gauge factor). In practice, the gauge is placed in a Wheatstone bridge to turn that tiny resistance change into a measurable voltage signal. This makes strain gauges the sensors that directly use strain-induced resistance changes to quantify mechanical deformation (and, by extension, force, pressure, or displacement through calibration). Other sensors listed rely on temperature effects (thermocouples, RTDs) or capacitance changes (capacitive sensors), not resistance changes due to strain.

The key idea is converting mechanical deformation into a change in electrical resistance. A strain gauge is designed for this. It uses a thin metallic foil or wire whose length and cross‑section change when the structure it’s bonded to is stretched or compressed. That change in geometry alters the resistance, with the fractional change ΔR/R proportional to the strain ε (ΔR/R ≈ GF × ε, where GF is the gauge factor). In practice, the gauge is placed in a Wheatstone bridge to turn that tiny resistance change into a measurable voltage signal. This makes strain gauges the sensors that directly use strain-induced resistance changes to quantify mechanical deformation (and, by extension, force, pressure, or displacement through calibration). Other sensors listed rely on temperature effects (thermocouples, RTDs) or capacitance changes (capacitive sensors), not resistance changes due to strain.