Wheatstone measuring bridge with strain gauge

Presentation of videos during practical training in biomechanics,
Strain gauge experiment

Notes: The strain gauges have nominal resistances of 120 or 350 ohms. The measuring bridges for the quarter and half bridge are supplemented by constant resistors to form a full bridge. In order to clearly emphasise the effect of stretching or compression (negative stretching), exaggeratedly large voltage changes were deliberately selected. In practice, the resistance changes and thus the voltage changes are so small that so-called bridge measuring amplifiers are used, which not only amplify the bridge measuring voltage, but also ensure a highly constant bridge supply voltage. The following variables can be measured with strain gauges:

Strain/compression
Torque/torsion
force
pressure

Temperature compensation is achieved through special wiring and arrangement of the strain gauges on the measurement object, i.e. temperature expansions cancel each other out, and certain expansion components, e.g. transverse expansion, can also be compensated or selected.

Quarter bridge with a strain gauge

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Note: Only 2 measuring leads required, single measured value, no temperature compensation

Half bridge with two strain gauges

Note: 3 measuring leads required, double measured value, temperature compensation

Full bridge with four strain gauges

Note: 4 measuring leads required, 4-fold measured value, temperature compensation
Note: With so-called 6-wire wiring, the voltage drop in the bridge supply can be readjusted by the bridge measuring amplifier using two additional measuring leads for long supply lines .

Idea/concept: K.H. Gatzweiler
Realisation/animation: S. Neumann