Table Of Contents
Half-Bridge Type I
Version:
Last Modified: August 7, 2018
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
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.