Electrical – Question about a Wheatstone bridge

It isn't a good idea to use resistive temperature sensors this way because of the large change in resistance will delinearize the bridge whether current fed or voltage fed. Devices like strain gauges bearly change their resistance at all and can be ok as a single active element in a bridge but not RTDs.

So, use the three wire connection and use a constant current feed. This is the most accurate method for RTDs. If you do a double measurement of the two wires feeding the sensor you can determine cable volt drop. If volt drop is minimal or constant use a two wire connection.

Because your RTD is four wire use an instrumentation amplifier or use it in 2-wire mode or 3-wire mode.

Your current source should be referenced to your ADC ref voltage if using an ADC with an inaccurate reference.

When a bridge is balanced, you know that there is no voltage between Va and Vb, and as a consequence, there is no current flowing between them as well. This vastly simplifies the circuit analysis, making it easy to determine the unknown component(s) relative to the known ones.

For small values of imbalance, it is possible to linearize the analysis around the balance point, which retains some of the simplicity, but for large values of imbalance, you're forced to do the full analysis of the entire circuit. It can be done, but you've given up all the advantage of using a bridge in the first place. Other circuit topologies would actually be simpler to analyze.