Types of thermocouple measurement connections
There are four types of thermocouple connection construction:
- Ground thermocouple connection
- Uncoated thermocouple fittings
- Exposed thermocouple junction
- Isolated thermocouple connection
Ground thermocouple connection
The ground thermocouple junction is an integral part of the thermocouple sheath tip
- Quick response time in relation to groundless and disconnected connections
- Protects wires from chemicals and corrosion of the environment
- The operating life of the thermocouple is longer. Longer lifespan of exposed thermocouples
- Recommended for high pressure applications
- This is the cheapest construction
- The thermal expansion of the pod material may be different from the element to cause mechanical stress and harden the metals.
- Earth rings can disrupt instruments
- Faulting in insulation is more difficult to detect
Uncoated thermocouple fittings
The junction of the baseless thermocouple is isolated from electrical insulation and from external electrical material. In a dual baseless thermocouple, a common electrical insulation connection is outside the sheath.
- The junction of the thermocouple is separated from the ground.
- By measuring the resistance from the ring to the sheath, MgO insulation defects can be detected.
- Prolonged traction is minimized in cycling conditions
- Response time is usually slower than ground thermocouples
- More expensive than ground thermocouples.
Exposed thermocouple junction
The thermocouple junction is exposed beyond the protective metal sheath
- Recommended for measuring non-corrosive static gas or air.
- Very fast response time, faster than ground connection
- Because the joint is exposed to this environment, it can not be used in an environment with a high percentage of solids, high pressure or lubricants.
Isolated thermocouple connection
Isolated thermocouple fittings A double or triple thermocouple is used when the fittings are separated from the outer sheath material as well as from each other.
- The elements are insulated from the ground.
- In a cycling environment, thermal works better than groundless or ground connections.
- Reaction time slower than a dualterrestrial thermocouple .
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