When placing sensors in high pressure or vacuum chamber, they should be terminated by an epoxy sealed terminal block interface on the system. 4 wire RTD is best for such applications, as multiple terminations and junctions are involved; also the wires may have to run some distance.
When measuring temperature in a big surface or object, use multiple sensors. An indicating scanner-controller can be used or ensure cooling-heating is uniform using fluids or air circulation.
RTD Sensors to Terminal Block Connections
W – is White Wire from RTD, R – is Red Wire from RTD, Color of Wire on RTD Sensor Pt-100.
Top 3 Terminals are for RTD 1 (Red), Bottom 3 Terms. are for RTD 2 (Yel), Marked with Color Tape.
The RTD two whites go to one end of the Platinum 100 ohms resistive sensor, the red goes to other end. The red in this sensor goes to gnd of opamp circuit in controller. Thru one white a 1mA current is injected, the other white gives a voltage output to opamp. This voltage after offset and calibration is proportional to temperature.