Use Wheatstone bridge to measure unknown resistance
This is my answer to SE EE question Use Wheatstone bridge to measure unknown resistance My answer A new look at the old bridge Can we now, in the 21st century, look at this famous 19th century device from a different perspective? Let's try... we won't lose anything from this... we will only gain… There were no precise sources then (neither voltage nor current)... nor precise voltmeters. So they had to find a way to compensate for the errors (mainly because of the varying supply voltage). For this purpose, they used the principle of negative feedback but implemented manually. So, the so-called "balanced bridge" and the man moving the rheostat's wiper or switching the resistors inside the box is a "negative feedback system". Its main purpose is to convert an unknown resistance Rx into another known (readable, measurable) resistance Rvar. It make it by keeping equal the ratios of two voltage dividers. From this point of view, the balanced bridge can be c...