Each of these temperature sensing methods has it's own individual characteristics; thermocouples can operate over greater temperature ranges whilst RTD's are more accurate and have greater stability in the long term.
Temperature ranges: Thermocouples, between -200 degrees C & +1700 degrees C. RTD's between -220 degrees C & +850 degrees C.
Accuracy: Up to 0.75 on mid-range systems.
Materials of contruction: To suit application e.g. steel, stainless steel, aluminium. Sheaths, steel, special alloys, ceramics.
Some options: Intrinsically safe; curved or angled probes; inbuilt transmitters.
A range of converters is available from transmission and conversion of resistance values and current or voltage signals. Some units have two voltage free contracts.