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Strain gauge connections and bridge circuits

Strain gauge connections and bridge circuits

How to wire a strain gauge depends on the type of instrument. See the table below for combinations of measurement method and bridge circuit.

Measuring mode example	Wiring connection to Switching Box	Wiring connection to Bridge Box	Bridge Output
Quarter bridge			E : Input voltage e : Output voltage ⊿e : Output voltage due to strain e₀ : Output voltage before strain occurrence R₀ : Resistance before strain occurrence ⊿R : Resistance change due to strain ε : Strain amount K : Gauge Factor of strain gauge e = e₀＋⊿e R₁ = R₀＋⊿R R = R₀
Quarter bridge 3-wire Compensates change in lead wire resistance due to temperature
Quarter bridge 3-wire width two gauges connected in series in one arm, eliminating bending strain			R₁ = R₀＋⊿R R₂ = R₀＋⊿R R = 2R₀
Quarter bridge width four gauges connected in series and paralleled in one arm			R₁ = R₂ = R₃ = R₄ = R₀＋⊿R R = R₀
Half bridge width 1-active and 1-dummy gauge			R₁ = R₀＋⊿R R₂ = R₀ = R
Half bridge width two active gauges			R₁ ＝R₀＋⊿R R₂ ＝R₀－ν⊿R ν : Poisson's ratio
Half bridge width 2 active gauges : Bending strain			R₁ = R₀＋⊿R R₂ = R₀ー⊿R R = R₀
Half bridge common dummy Sharing to multiple channels with R₂ as common dummy		Only for switching box	R₁ = R₀＋⊿R R₂ = R₀ = R
Opposite arm Half bridge with 2 active gauges	Only for bridge box Accommodated models SB-120B SB-128A SB-123A		R₁ = R₀＋⊿R R₂ = R₀＋⊿R R = R₀
Opposite arm Half bridge with 3-wire 2 active gauges	Only for bridge box Accommodated models SB-120B SB-128A SB-123A		R₁ = R₀＋⊿R R₂ = R₀＋⊿R R = R₀
Full bridge width 4 active gauges : Uniaxial strain			R₁ = R₃＝R₀＋⊿R R₂ = R₄＝R₀－v・⊿R ν : Poisson's ratio
Full bridge width 4 active gauges : Bending strain			R₁ = R₃＝R₀＋⊿R R₂ = R₄＝R₀ー⊿R ⊿e = EKε
Full bridge width 4 active gauges : Torque			R₁ = R₃＝R₀＋⊿R R₂ = R₄＝R₀ー⊿R ⊿e = EKε
Full bridge width 2 active and 2 dummy gauges			R₁ = R₃＝R₀＋⊿R R₂ = R₄＝ R R = R₀