Calculate the bridge output voltage and ratio U_M/U_B exactly from the four arm resistances and the excitation.
Enter values and run the calculation.
The bridge is two voltage dividers on the same excitation; the output is the difference of the two divider voltages. Hence equal-sign resistance changes in adjacent arms cancel while those in opposite arms add. For small changes eq. 4.1 reduces to the linearised basic equation 4.6.
U_M/U_B = R₁/(R₁+R₂) − R₄/(R₃+R₄) (Keil Gl. 4.1)
Abgleich: R₁/R₂ = R₃/R₄
R_in = (R₁+R₂)‖(R₃+R₄)
Assigning the arms incorrectly: R₂ and R₄ are adjacent to R₁, R₃ is opposite; swapping flips the sign.
Checking zero errors caused by resistance tolerances, sizing balancing resistors and verifying the signal a resistance standard produces in one arm.
Constant-voltage excitation and an unloaded measuring diagonal (high-impedance amplifier input). Constant-current excitation or a low-impedance load require different relations.
Keil, Dehnungsmessstreifen, 2nd ed. 2017, secs. 4.1–4.2, eqs. (4.1)–(4.6).
The source supports the equation structure and worked examples; this calculator does not replace calibration of the measuring chain.
There an unknown resistance is found from balance; here the output of the deliberately unbalanced bridge is computed, as used in strain-gauge measurement.
Because U_M is proportional to U_B; the ratio characterises the bridge independently of the excitation.
Only approximately; with one active arm eq. 4.7 gives an error equal in size to the strain itself.