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:
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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.
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Completion resistors which provide half-bridge completion.
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Sensitivity to both axial and bending strain.
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Compensation for temperature.
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Compensation for the aggregate effect on the principle strain measurement due to the Poisson's ratio of the material.
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Sensitivity at 1000 µε is ~ 0.65 mVout/ VEX input
Half-Bridge Type I Circuit Diagram
The following symbols apply to the circuit diagram:
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R1 is the half-bridge completion resistor.
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R2 is the half-bridge completion resistor.
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R3 is the active strain gage element measuring compression due to the Poisson effect (–ε).
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R4 is the active strain gage element measuring tensile strain (+ε).
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VEX is the excitation voltage.
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RL is the lead resistance.
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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.