Thermocouple Grounded Or Ungrounded

[SmokinSignals]

What is the consensus on which type of thermocouple to use in the DBS if you are running your own PID.  I know the brand most like is Omega, what I am looking for is whether or not to get a grounded or ungrounded probe for better response.  Thanks in advance.

[TedEbear]

I use an Auber K-type TC with alligator clip, model TC-K6A.

[pensrock]

Some information: I have seen problems occur in high temperature sintering furnaces if using a grounded tip T/C if the tip touches any metal. This is not always true but does happen. In my experience a thinner ungrounded T/C will have very good response time compared to a larger diameter T/C. I use a type J thermocouple that is ungrounded and 1/8" diameter in my Bradley and it works very well.
Thermocouple Junctions:
The grounded junction is recommended for the measurement of static or flowing corrosive gas and liquid temperatures and for high pressure applications. The junction of a grounded thermocouple is welded to the protective sheath giving faster response than the ungrounded junction type.

An ungrounded junction is recommended 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).

An exposed junction is recommended for the measurement of static or flowing non-corrosive gas temperatures where fast response time is required. The junction extends beyond the protective metallic sheath to give accurate fast response. The sheath insulation is sealed where the junction extends to prevent penetration of moisture or gas which could cause errors.

[beefmann]

Some information: I have seen problems occur in high temperature sintering furnaces if using a grounded tip T/C if the tip touches any metal. This is not always true but does happen. In my experience a thinner ungrounded T/C will have very good response time compared to a larger diameter T/C. I use a type J thermocouple that is ungrounded and 1/8" diameter in my Bradley and it works very well.
Thermocouple Junctions:
The grounded junction is recommended for the measurement of static or flowing corrosive gas and liquid temperatures and for high pressure applications. The junction of a grounded thermocouple is welded to the protective sheath giving faster response than the ungrounded junction type.

An ungrounded junction is recommended 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).

An exposed junction is recommended for the measurement of static or flowing non-corrosive gas temperatures where fast response time is required. The junction extends beyond the protective metallic sheath to give accurate fast response. The sheath insulation is sealed where the junction extends to prevent penetration of moisture or gas which could cause errors.

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