Wheatstone Bridge Calculator

A Wheatstone bridge consists of two parallel resistor branches connected to a single voltage source. When the bridge is balanced, the ratio of resistances in one branch equals the ratio in the other branch, resulting in zero bridge voltage. The core equation for finding an unknown resistance ($R_x$) when the bridge is balanced is expressed as: $R_x = (R_3 / R_1) \times R_2$. When calculating output bridge voltage ($V_{out}$) under unbalanced conditions, the formula is: $V_{out} = V_{in} \times [R_x / (R_3 + R_x) - R_2 / (R_1 + R_2)]$.

Imagine you are analyzing a circuit where your input voltage ($V_{in}$) is 10 volts. You have three known resistors: $R_1 = 100\ \Omega$, $R_2 = 100\ \Omega$, and $R_3 = 200\ \Omega$. You want to find the unknown resistor $R_x$ to achieve a balanced bridge. Using the balanced condition formula, $R_x = (R_3 / R_1) \times R_2$, we substitute the values: $R_x = (200 / 100) \times 100$. This simplifies to $2 \times 100$, giving us an unknown resistance of $200\ \Omega$. If any value changes and creates an imbalance, the bridge voltage formula will instantly quantify the exact electrical potential difference across the output terminals.

Always verify your resistor tolerance values before performing calculations, as component variance can affect real-world bridge precision. Ensure that your input voltage does not exceed the power rating of your resistors to prevent thermal drift or component failure. When measuring low resistances, account for lead wire resistance to maintain high measurement accuracy.