Wheatstone Bridge Calculator
Wheatstone bridge balance / output: solve the unknown arm from three resistors, or compute offset voltage, Thevenin resistance, and sensitivity from all four arms.
Key points
Wheatstone Bridge Calculator: Wheatstone bridge balance / output: solve the unknown arm from three resistors, or compute offset voltage, Thevenin resistance, and sensitivity from all four arms. Formula: R1·Rx = R2·R3 | Vout = Vex·[R3/(R1+R3) − Rx/(R2+Rx)] | Rth = R1∥R3 + R2∥Rx. Enter parameters on the DD-CAT IDE online tool page to get results instantly, with a calculation-model diagram that updates with the inputs. Balance requires R1·Rx = R2·R3 (i.e. R1/R2 = R3/Rx); with three arms known, solve the fourth. When unbalanced, Vout = VA−VB and scales with excitation; sensitivity is often given in mV/V, and strain-gauge bridges often produce only 1–3 mV/V at full scale.
Inputs
R1·Rx = R2·R3 | Vout = Vex·[R3/(R1+R3) − Rx/(R2+Rx)] | Rth = R1∥R3 + R2∥RxCalculation model (updates with parameters)
| Rx at balance | 10 kΩ | R2·R3/R1 |
| Unknown resistance Rx | 10 kΩ | Solved from the balance condition |
| Left midpoint voltage VA | 2.5 V | Vex·R3/(R1+R3) |
| Right midpoint voltage VB | 2.5 V | Vex·Rx/(R2+Rx) |
| Offset voltage Vout = VA − VB | 0 V | Positive means the left midpoint is higher than the right |
| Bridge sensitivity Vout/Vex | 0.000 mV/V | Differential output per unit excitation |
| Deviation from balance | 0.000 % | Negative means Rx is low; positive means Rx is high |
| Thevenin equivalent resistance Rth | 10 kΩ | R1∥R3 + R2∥Rx; the next-stage input impedance should be much larger |
| Common-mode voltage Vcm | 2.5 V | (VA+VB)/2; check the common-mode range when choosing an instrumentation amplifier |
| Left / right arm current | 250 µA / 250 µA | Vex/(R1+R3) / Vex/(R2+Rx) |
| Total bridge dissipation | 2.5 mW | 左 1.25 mW + 右 1.25 mW |
Engineering notes
- Balance requires R1·Rx = R2·R3 (i.e. R1/R2 = R3/Rx); with three arms known, solve the fourth.
- When unbalanced, Vout = VA−VB and scales with excitation; sensitivity is often given in mV/V, and strain-gauge bridges often produce only 1–3 mV/V at full scale.
- Bridge output resistance Rth = R1∥R3 + R2∥Rx; the next stage must have much higher input impedance. Use an instrumentation amplifier for high-resistance arms.
- Lead and contact resistance and arm tolerance directly shift the balance point; use four-wire measurement for low resistance and ratio arms plus a stable reference for high precision.
FAQ
- What is Wheatstone Bridge Calculator for?
- Wheatstone bridge balance / output: solve the unknown arm from three resistors, or compute offset voltage, Thevenin resistance, and sensitivity from all four arms.
- What is the formula for Wheatstone Bridge Calculator?
- Core formula: R1·Rx = R2·R3 | Vout = Vex·[R3/(R1+R3) − Rx/(R2+Rx)] | Rth = R1∥R3 + R2∥Rx. The tool returns results instantly using this formula and the selected parameters.
- What engineering notes should I keep in mind when using Wheatstone Bridge Calculator?
- Balance requires R1·Rx = R2·R3 (i.e. R1/R2 = R3/Rx); with three arms known, solve the fourth. When unbalanced, Vout = VA−VB and scales with excitation; sensitivity is often given in mV/V, and strain-gauge bridges often produce only 1–3 mV/V at full scale. Bridge output resistance Rth = R1∥R3 + R2∥Rx; the next stage must have much higher input impedance. Use an instrumentation amplifier for high-resistance arms. Lead and contact resistance and arm tolerance directly shift the…