How should the bridge factor be selected when using strain gauges?

The number of active arms in a strain gauge Wheatstone bridge is known as the bridge factor.

As a simple guide when selecting bridge factors the following rules apply;

  • When using 1/4 bridge completion the bridge factor should be set to 1
  • When using 1/2 bridge completion the bridge factor should be set to 2
  • When using full bridge completion the bridge factor should be set to 4

However, it is important to note that these simple rules only apply when the strain gauges are configured in a particular way.

The physical layout of the gauges affects the bridge factor.

If, for example, they are mounted in a transverse configuration for temperature compensation or are mounted on a shaft for torsional analysis then different, and more complex, rules can apply.

Traditionally, due to the nature of the small voltage changes associated with strain gauges any change in amplifier gain or change in excitation voltage should be followed by a calibration.

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James Wren

Application Engineer & Sales Manager at Prosig
James Wren is an Application Engineer and the Sales Manager for Prosig Limited. James graduated from Portsmouth University in 2001, with a Masters degree in Electronic Engineering. He is a Chartered Engineer and a registered Eur Ing. He has been involved with motorsport from a very early age with special interest in data acquisition. James is a founder member of the Dalmeny Racing team.

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