⚖️ Wheatstone Bridge Calculator

Calculate unknown resistances, analyze bridge balance conditions, and design precision measurement circuits using Wheatstone bridge principles.

Calculation Type

Input Parameters

Wheatstone Bridge - Unknown Resistance
Rx = R2 × R3 / R1
Calculate unknown resistance when bridge is balanced
R1 ——— R2
| |
| G |
| |
Rx ——— R3
Bridge Circuit (G = Galvanometer)

Results & Analysis

Enter values and click Calculate to see Wheatstone bridge analysis results

Wheatstone Bridge Theory

Balance Condition

A Wheatstone bridge is balanced when no current flows through the galvanometer.

  • R1 × R3 = R2 × Rx (balance equation)
  • Galvanometer current = 0
  • High precision measurement
  • Independent of supply voltage

Strain Measurement

Strain gauges change resistance proportionally to applied strain.

  • ΔR/R = GF × ε (gauge equation)
  • Bridge output ∝ applied strain
  • Temperature compensation
  • High sensitivity measurement

Applications

  • Resistance Measurement: Precise unknown resistance
  • Strain Gauges: Force and pressure sensors
  • Temperature Sensors: RTD measurements
  • Load Cells: Weight measurement systems

HOW TO USE

Enter three known resistances (R1, R2, R3) and the supply voltage. Click Calculate to find the unknown resistance (Rx) and galvanometer current at balance condition.

FORMULA USED

Balance condition: R1/R2 = R3/Rx → Rx = (R2 × R3) ÷ R1
Galvanometer current when unbalanced: Ig = V × (R1×R4 - R2×R3) ÷ (various terms)

WORKED EXAMPLE

R1=100Ω, R2=200Ω, R3=150Ω. Unknown Rx = (200 × 150) ÷ 100 = 300 Ω. The bridge is balanced when all ratios are equal.

FREQUENTLY ASKED QUESTIONS

Q: What is a Wheatstone Bridge?

A: A Wheatstone Bridge is a circuit used to measure an unknown resistance precisely by balancing two legs of a bridge circuit.

Q: What is the balance condition?

A: The bridge is balanced when R1/R2 = R3/Rx, meaning no current flows through the galvanometer. This gives Rx = R2×R3/R1.

Q: What is a galvanometer?

A: A galvanometer is a sensitive current detector. In a Wheatstone bridge, it indicates when the bridge is balanced (zero current).

Q: What are modern applications of Wheatstone Bridge?

A: Strain gauges, temperature sensors (RTD), pressure sensors, and load cells all use Wheatstone bridge circuits.