Wheatstone bridge
In many cases, the change in the sensor voltage during a measurement is very small. If the input voltage fluctuates or if it contains noise which has the same order of magnitude of the change of the signal, it is impossible to have a good sensor readout by using a simple voltage divider circuit. A solution for this is to use a Wheatstone bridge. Another advantage of the Wheatstone bridge is that the measurement sensitivity is linear.

A Wheatstone bridge has two branches which both act as a voltage divider. It contains four resistors. Depending on the application, one or more of the resistors get replaced by a sensor whose resistance depends on the physical quantity one wants to measure.

In order to obtain the voltage difference between two signals, a differential amplifier can be used. As is explained on the page devoted to differential amplifiers, this solution also has some disadvantages. Especially with high precision measurements those disadvanteges will cause trouble, instead an instumentation amplifier should be used. Both the differential and instrumentation amplifier output a voltage which is proportional to the difference between the input voltage. This makes them ideal for reading out a Wheatstone bridge.