Half-Bridge Type I

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 mV_out/ V_EX 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).
• V_EX is the excitation voltage.
• R_L is the lead resistance.
• V_CH is the measured voltage.

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

where V_r 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, R_L is the lead resistance, and R_g is the nominal gage resistance.