# 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.

The voltage output of the wheatstone bridge VG is given by

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

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

$$ΔV_G = -V_S [{ΔR \over {4R + 2ΔR}}]$$

Thank you for learning from electronics-course.com

We do not have a paywall as our mission is to provide everyone from Albania to Zimbabwe, rich or poor, a quality foundational electronics education. With advertising revenues falling despite increasing numbers of learners, we need your help to maintain and improve the course, which takes time, money and hard work.

If everyone who benefits from this course gives as little as \$2 via Paypal, we can continue to achieve our mission. Thanks!