A grounded junction is electrically connected to the sheath. An ungrounded junction is isolated from it. This distinction affects the measurement chain, including required response, whether the sheath can contact another grounded part of the installation, and whether electrical noise could affect the receiving instrument. Consider the junction with the thermocouple type, sheath, cable, process point and instrument input. The junction's physical location also matters when the sensor is mounted against a surface or inside a process assembly.
The catalogue lists both options for several products. Thermocouple MI lists J and K types with grounded and ungrounded junction choices. The Jubilee-clip surface thermocouple also lists J and K with grounded and ungrounded junctions, while its cable options include Tef/Tef and Fg/Fg/SS. The pipe temperature thermocouple lists K, J, T and RTD choices and grounded or ungrounded (isolated) junctions. Junction choices are product-specific; other assemblies may differ. Check each product listing for its own sheath, dimensions and cable details.
Selection is a measurement-point decision. A surface or pipe probe may need a mounting arrangement that keeps the junction in the intended contact position. A process probe may need its junction, sheath, cable and connection reviewed as one assembly. Check whether the receiving input is configured for the selected type, how the installation is grounded, and where the cable runs relative to other electrical equipment. Also identify whether the point is accessible for inspection or replacement. Note nearby drives, switching equipment or other possible sources of interference.
When comparing the two junction styles, do not use response alone as the deciding factor. Electrical isolation, grounding arrangement, cable construction and instrument compatibility may be equally important. Provide the thermocouple type, sheath requirement, point location, mounting method, cable route and instrument input with an enquiry. Check the selected product's listing for the junction choices and dimensions it specifies. Include the intended purpose of the reading and any existing connector or wiring detail so the comparison addresses the complete measurement chain. A replacement enquiry should also identify the current junction and cable arrangement.