Selection of the Measuring Junction

Sheathed thermocouples are available in 3 junction types: grounded, ungrounded, and exposed. Each design offers specific advantages as well as disadvantages and must be considered carefully when placing an order. 

Grounded  Junction

The thermo-elements are welded into the end cap using the same weld rod as the sheath material. Fast time response. Recommended

for high pressure applications, liquids, moisture, contaminating atmospheres, and most general uses. 

Disadvantage: Can Be subject to EMF interference. 

Ungrounded Junction

The thermo-elements are welded together and are electrically isolated from the sheath. Recommended for applications where stray EMF's from electrical apparatus would affect the reading. 

Disadvantage: Slower Response Time. 

Exposed junction

The thermo-elements are welded together outside of the sheath. This provides the fastest time response, but exposes the elements to contamination. Electrically isolated from the sheath. 

Disadvantage: Cannot be used in an environment with a high percentage of solids, high pressure, or liquid material since the junction is exposed to this environment. 

Response times

Values are for 2/3 of total temperature change from 0 to 100% as measured in water. 20-AWG bare wire junction measured in gas. 

Outside DiameterApproximate Wire GaugeApproximate Wall ThicknessGrounded JunctionUngrounded Junction
20 AWG bare wire junction                                                                                                                                                                .45