In our daily lives, from supermarket electronic scales and tyre pressure monitoring systems in cars to bridge health monitoring systems, there is often a common core component at their heart: the strain gauge. Its operating principle is based on a physical phenomenon known as the strain effect: when a metallic conductor (typically formed as a grid of foil wires) undergoes minute mechanical deformation (stretching or compression) alongside an elastic material, its resistance value changes accordingly.
Specifically, the strain gauge is firmly bonded to the surface of the elastic material requiring strain measurement using a special adhesive. When the elastomer deforms under applied force, the strain gauge deforms synchronously. This alters the length and cross-sectional area of its internal metal grid wires, inducing a minute change in resistance denoted as ΔR. This resistance change (ΔR) is directly proportional to the strain (ε) of the elastomer—the deformation per unit length—with the proportionality constant termed the sensitivity coefficient (K). Through a Wheatstone bridge circuit, this minute resistance change is converted into a measurable voltage signal. Following amplification by an amplifier and subsequent calculation, the magnitude of the applied force can be derived.
It is precisely due to its outstanding precision, reliability, and capability to measure both static and dynamic strain that resistive strain gauge technology has endured since its invention in the mid-20th century. It remains not only the standard instrument for laboratory material mechanics testing but also forms the foundation of hundreds of millions of industrial force measurement and load cell sensors. Its applications range from miniature sensors capable of measuring intercellular forces to massive vehicle scales weighing hundreds of tonnes, yet its core principle remains constant throughout. Truly, it stands as the unsung hero of the modern sensing world.
