Balanced Bridge Circuit:

The balanced bridge circuit uses a galvanometer to compare the RTD resistance along with in which of a fixed resistor. A galvanometer uses a pointer that deflects on either side of zero when the resistance of the arms is not equal. A resistance of the slide wire is adjusted until the galvanometer denotes zero. The value of the slide resistance is then used to determine the temperature of the system being monitored.

Figure: Balanced Bridge Circuit

A slidewire resistor is used to balance the arms of the bridge. A circuit will be in balance whenever the value of the slidewire resistance is like that no current flows by the galvanometer.  To each temperature change, there is a new value; thus, the slider has to be moved to a new position to balance the circuit.