Strain gauge sensor (resistive strain sensor, strain gauge) is a device for measuring the stress condition of metal. It is designed as a special form conductor that is connected to the measured product. Knowing the sensor resistance in the non-strained state, it is possible to determine the strain degree based on resistance change.
Before invention of strain gauge sensors, the industry mostly used mechanical lever scales for weighing.
Mechanical scales offered two methods of weighing: a balancing mechanism or a mechanism for measuring force based on mechanical levers. The very first load cells for weighing, developed before the strain gauge sensors, were hydraulic or pneumatic. In 1843, an English physicist Charles Wheatstone invented a bridge for measuring the electric resistance of conductors. Wheatstone bridge became an ideal instrument for measuring the resistance changes occurring in the strain gauge sensors.
Despite the fact that the first strain gauge sensor was invented in the 40-s of the last century, its production became economically and technically feasible only when electronics advanced enough. Ever since, the strain gauge sensors became integral components of mechanical scales and independent load sensors. Simplicity of sensor connection to a strain gauge module allows to assemble the entire measuring complexes. Smart strain gauge sensors allow to directly obtain the measured value, thus eliminating the need to configure the measuring channels.
Nowadays, the strain gauge sensors predominate in the weight measuring equipment industry. However, some laboratories still use the precise balancing scales.