Half-Bridge Type I

NI-DAQmx 18.6 Help


Edition Date: January 2019
Part Number: 370466AH-01
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The following figure shows how to position strain gage resistors in an axial configuration for the half-bridge type I.



The following figure shows how to position strain gage resistors in a bending configuration for the half-bridge type I.



Half-bridge type I strain gage configurations have the following characteristics:
  • Two active strain gage elements, one mounted in the direction of axial strain and the other acting as a Poisson gage and mounted transverse, or perpendicular, to the principal axis of strain.
  • Completion resistors which provide half-bridge completion.
  • Sensitivity to both axial and bending strain.
  • Compensation for temperature.
  • Compensation for the aggregate effect on the principle strain measurement due to the Poisson's ratio of the material.
  • Sensitivity at 1000 µε is ~ 0.65 mVout/ VEX input
Related concepts

Half-Bridge Type I Circuit Diagram



The following symbols apply to the circuit diagram:
  • R1 is the half-bridge completion resistor.
  • R2 is the half-bridge completion resistor.
  • R3 is the active strain gage element measuring compression due to the Poisson effect (–ε).
  • R4 is the active strain gage element measuring tensile strain (+ε).
  • VEX is the excitation voltage.
  • RL is the lead resistance.
  • VCH is the measured voltage.

The following equation converts voltage ratios to strain units for half-bridge type I configurations.



where Vr is the voltage ratio that virtual channels use in the voltage-to-strain conversion equation, GF is the gage factor, v is the Poisson's ratio, RL is the lead resistance, and Rg is the nominal gage resistance.

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