Emerson ROC827 - Manual (Page 90)

ROC827 Instruction Manual
Issued Mar-06 Input/Output Modules 4-20
Note
: Only ungrounded probes are supported. It is highly recommended
that you use sheathed probes.
Use an ungrounded junction for measurements in corrosive environments
where it is desirable to have the thermocouple electronically isolated from
and shielded by the sheath. The welded wire thermocouple is physically
insulated from the thermocouple sheath by MgO powder (soft).
At the tip of a grounded junction probe, the thermocouple wires
physically attach to the inside of the probe wall. This results in good heat
transfer from the outside, through the probe wall to the thermocouple
junction. Grounded wiring is not supported.
The thermocouple in the exposed junction protrudes out of the tip of the
sheath and is exposed to the surrounding environment. This type offers the
best response time, but is limited in use to non-corrosive and non-
pressurized applications. Exposed junction thermocouples are not
supported.
Note
: Avoid subjecting the thermocouple connections and measurement
instrument to sudden changes in temperature.