Table Of Contents
Quarter-Bridge Type I
Version:
Last Modified: August 7, 2018
The following figure shows how to position a strain gage resistor in an axial configuration for the quarter-bridge type I.
The following figure shows how to position a strain gage resistor in a bending configuration for the quarter-bridge type I.
Quarter-bridge type I strain gage configurations have the following characteristics:
- A single active strain gage element mounted in the principle direction of axial or bending strain.
- A passive quarter-bridge completion resistor, known as a dummy resistor, in addition to half-bridge completion.
- Temperature variation decreasing the accuracy of the measurements.
- Sensitivity at 1000 µε is ~ 0.5 mVout / VEX input.
Quarter-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 quarter-bridge completion resistor, known as a dummy resistor.
- 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 quarter-bridge configurations.
where Vr is the voltage ratio that virtual channels use in the voltage-to-strain conversion equation, GF is the gage factor, RL is the lead resistance, and Rg is the nominal gage resistance.