What are Multipoint Thermocouples?

Multipoint thermocouples accurately measure temperature at various locations along the length of the sensor. They are particularly useful for detecting hotspots and uneven flow and are used in a variety of applications where there is a large or complex process and correct temperature management is critical.

Temperature gradients always exist regardless of the process. In many processes sensing temperature at a single location is adequate as variations in the temperature gradient will not cause issues in the process. However, in many applications, including profiling in furnaces, process lines, chemical reactors, oil refineries and petrochemical industries, there is the need to measure and monitor temperature in multiple locations, to ensure the process is cost efficient, accurate and safe.

Pyrosales custom design and manufacture multipoint thermocouples to the desired specifications. They are sturdy and reliable measurement sensors and are available in types K, J, E, T and N. Various sheath materials are available including, Stainless steel 304, 316, 347, Alloy 600 (Inconel™ 600) as well as Hastelloy C276, Hastelloy X, Stainless steel 210 and 321 and Nickel 200. The sheath material will determine the range of temperature that can be measured. Multipoint thermocouples can measure from -200°C to 1250°C. Thermocouples can be provided grounded or ungrounded.

The design of a C317 multipoint thermocouple includes the use of a hard packed MgO insulation, much the same as a traditional thermocouple. It uses a large single positive (+) conductor as the centre conductor and position multiple negative (-) conductors around it. This provides a smaller and more flexible package but with a larger conductor.

In the C329 design, each measurement point has both positive (+) and negative (-) conductors of the thermocouple unlike that of C317 where they have a single positive (+) conductor as the centre conductor and position multiple negative (-) conductors around it. This is achieved by swaging down the initial large cable. The space around the thermocouples is filled with hard pack MgO insulation, same as traditional Mineral Insulated thermocouple cables