Operating temperature increase, metallic alloys

In power compensated DSC the small size of the individual sample and reference holders makes for rapid response. The temperature sensors are platinum (Pt) resistive elements. The individual furnaces are made of Pt/Rh alloy. It is important that the thermal characteristics of the sample and reference assemblies be matched precisely. The maximum operating temperature is limited to about 750 °C. High temperature DSC measurements (750-1600°C) are made by heat flux instruments using thermocouples of Pt and Pt/Rh alloys. The thermocouples often incorporate a plate to support the crucible. The use of precious metal thermocouples is at the expense of a small signal strength. Both chromel/alumel and chromel/constantan are used in heat flux DSC equipment for measurements at temperatures to about 750 °C. Multiple thermocouple assemblies offer the possibility of an increased sensitivity - recently a 20-junction Au/Au-Pd thermocouple assembly has been developed. Thermocouples of W and W/Re are used in DTA equipment for measurements above 1600°C. The operating temperature is the predominant feature which determines the design and the materials used in the con-... 

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