Sensor that changes its electrical resistance in proportion to the mechanical strain under load. Strain gauges are suitable for the electrical measurement of all mechanical variables that can produce strain in the sensor.
A differentiation is made between metal strain gauges (thin foil strain gauge or thick film technology) - which is used the most these days - and semiconductor strain gauges.
Metal strain gauges have the advantage of absolute linearity in the region of Hook's straight lines and provide a simple means of compensation for temperature drift. Due to the extremely small resistance changes it is, however, necessary to amplify the output signals appropriately, which requires special measuring amplifiers.
Strain gauges are available in numerous variants including diaphragms on which four strain gauges are connected to form a Wheatstone bridge in which negative and positive position changes add together in the output signal (Figure D 9).
Figure D 9: Diaphragm as thin foil strain gauge