A Wheatstone bridge is an arrangement of 4 resistors used to measure the resistance of strain gauges. Wheatstone bridges provide better accuracy than directly measuring the resistance of a single strain gauge. Of their 4 resistors, either 1, 2 or 4 are strain gauges and the remainder are regular resistors. we call these Wheatstone bridges, quarter, half and full bridges respectively. The resistance values of the fixed resistors should be same as those of the strain gauges at rest. The improvement in accuracy obtained by using a Wheatstone bridge depends on the type of bridge (quarter, half or full) and to some extent, the layout of the stain gauges on the beam or shaft. The increased accuracy obtained through use of a Wheatstone bridge is as a result of the following:

Illustration of Wheatstone bridge resistor arrangement
  • Increased sensitivity: The increased sensitivity improves the effective resolution and reduces measurement error
  • Temperature compensation: When using 2 or 4 strain gauges, the effect on the resistance of variations in ambient temperature are cancelled out
  • Common mode noise rejection: Electrical Noise common to both sides of the bridge is cancelled out
  • Strain decoupling: Wheatstone bridges with 2 or 4 strain gauges are able to separate the bending strain from the normal strain

Using a Wheatstone Bridge

The following diagrams demonstrate how to setup Wheatstone bridges for measuring bending strain, tensile/compressive strain and torsional strain. There are additional stain gauge configurations, but the ones shown cover the majority of scenarios. Note: The table under each equation shows the bridge factor. The bridge factors have already been factored into the equations and so no further action is required.

Glossary of terms

1. Beam bending strain measurement: Quarter bridge

Quarter bridge Wheatstone bridge strain gauge arrangement for measuring bending strain
SensitivityStrain decouplingCommon mode RejectionTemperature compensation
LowNoNoNo

2. Beam bending strain measurement: Half bridge

Half bridge Wheatstone bridge strain gauge arrangement for measuring bending strain
Sensitivity Strain decoupling Common mode Rejection Temperature compensation
MediumYesNoYes

3. Beam bending strain measurement: Full bridge

Full bridge Wheatstone bridge strain gauge arrangement for measuring bending strain
Signal sensitivityStrain decouplingCommon mode RejectionTemperature compensation
Highyesyesyes

4. Compressive or tensile strain measurement: Quarter bridge

Quarter bridge Wheatstone bridge strain gauge arrangement for measuring tensile strain
Signal sensitivityStrain decouplingCommon mode RejectionTemperature compensation
LowNANoNo

5. Compressive or tensile strain measurement: Half bridge

Half bridge Wheatstone bridge strain gauge arrangement for measuring tensile strain
Signal sensitivityStrain decouplingCommon mode RejectionTemperature compensation
Medium NA NoYes

6. Compressive or tensile strain measurement: Full bridge

Full bridge Wheatstone bridge strain gauge arrangement for measuring tensile strain
Signal sensitivityStrain decouplingCommon mode RejectionTemperature compensation
High NA YesYes

7. Torsional strain measurement: Full bridge setup 1

Full bridge Wheatstone bridge strain gauge arrangement for measuring torsional strain
Signal sensitivityStrain decouplingCommon mode RejectionTemperature compensation
High NA YesYes

8. Torsional strain measurement: Full bridge setup 2

Full bridge Wheatstone bridge strain gauge arrangement for measuring torsional strain
Signal sensitivityStrain decouplingCommon mode RejectionTemperature compensation
High NA YesYes

Additional information

Wikipedia page on Wheatstone Bridges

Additional Wheatstone bridge layouts