Temperature Compensation:

Because of that's changes in ambient temperature and the resistance thermometer circuitry must be compensated.  The resistors which are used in the measuring circuitry are chosen so which their resistance will remain constant over the range of temperature expected. The Temperature compensation is also accomplished by the design of the electronic circuitry to compensate for ambient modify in the equipment cabinet. That is also possible for the resistance of the detector leads to modify due to a change in ambient temperature.  For compensate for this change, three and four wire RTD circuits are used.  With this way, the same amount of lead wire is used in both branches of the bridge circuit and the modifications in resistance will be felt on both branches, negating the effects of the make changes in temperature.