Wheatstone Bridge Circuit

The basic Wheatstone bridge circuit consists of two arms composed of two resistors in series. A source of excitation (voltage or current) is connected and the output is the difference between the outputs of the two voltage dividers. The Wheatstone bridge circuit is useful for measuring small changes in resistance like that of the strain gauge where typically less than 1% change occurs.

Wheatstone Bridge Circuit

The voltage output of the wheatstone bridge VG is given by

\begin{equation} V_G = V_S ({R_3 \over {R_3 + R_X}} - {R_2 \over {R_1 + R_2}}) \end{equation} \begin{equation} V_G = -V_S [{{R_X R_2 - R_1 R_3} \over {(R_1 + R_2)(R_3 + R_X)}}] \end{equation}

If the bridge is balanced VG = 0 since all the resistances are equal. When a change is applied to RX , RX becomes R + ΔR and substituting R to all the other resistances, the change in output voltage ΔVG is

\begin{equation} ΔV_G = -V_S [{ΔR \over {4R + 2ΔR}}] \end{equation}

With advertising revenues falling despite increasing numbers of learners, we need your help to maintain and improve this site, which takes time, money and hard work. Thanks to the generosity of our learners who gave earlier, you are able to use this site at no charge.

If you have benefited from this site and are able, please give via Paypal. It will allow us to continue into the future. It only takes a minute. Thanks!

US$ 2 US$ 5 US$ 10