Showing posts with label Insulated Thermocouples. Show all posts
Showing posts with label Insulated Thermocouples. Show all posts
Tuesday, July 10, 2012
Insulated Thermocouple Wire Considerations
There are many different types
of thermocouple wire insulation based on the specific application required for
each use. Generally, the larger the wire
diameter, the less flexible it will be.
The smaller the diameter flexibility increases but at the cost of
strength. The most common sizes are 20
and 24 awg solid or stranded. 30 and 36
awg sizes are also used for special applications. Stranding will increase the flexibility with
a minimal increase in overall diameter.
As you may assume the better the insulation is for temperature, moisture
and abrasion resistance, the higher the cost.
Monday, January 23, 2012
Compacted MgO Thermocouples
All Temprel MgO insulated thermocouples are made using the highest purity MgO for temperatures up to 2300F (1260C). The thermo-elements are all ANSI special limits of error to give your measurements the best possible results. The various sheath materials are dependent on the application and the following will help you make the best selection.
304 SS - Maximum temperature of 1650F (900C) and is the most widely used low temperature sheath material. It offers good corrosion resistance but is subject to carbide precipitation in the 900F to 1600F (480 to 870C) range.
310 SS - Maximum temperature of 2100F (1150C) and offers good mechanical and corrosion resistance similar to 304 SS. Very good heat resistance. Not as ductile as 304 SS.
316 SS - Maximum temperature of 1650°F (900C) and has the best corrosion resistance of the austenitic stainless steels. Subject to carbide precipitation in the 900F to 1600F (480 to 870C) range.
Inconel - Maximum temperature 2150°F (1175°C) and is the most widely used thermocouple sheath material. Good high temperature strength, corrosion resistance and is resistant to chloride-ion stress corrosion, cracking and oxidation. Do not use in sulfur bearing environments.
Hastelloy X – Maximum temperature 2200F (1205C) widely used in aerospace applications. Resistant to oxidizing, reducing and neutral atmospheric conditions. Excellent high temperature strength.
All MgO compacted thermocouples can be bent on a radius of twice the sheath diameter.
If you don't see what you are looking for here, or if you have additional questions please feel free to contact Temprel at 1-800-582-5098.
304 SS - Maximum temperature of 1650F (900C) and is the most widely used low temperature sheath material. It offers good corrosion resistance but is subject to carbide precipitation in the 900F to 1600F (480 to 870C) range.
310 SS - Maximum temperature of 2100F (1150C) and offers good mechanical and corrosion resistance similar to 304 SS. Very good heat resistance. Not as ductile as 304 SS.
316 SS - Maximum temperature of 1650°F (900C) and has the best corrosion resistance of the austenitic stainless steels. Subject to carbide precipitation in the 900F to 1600F (480 to 870C) range.
Inconel - Maximum temperature 2150°F (1175°C) and is the most widely used thermocouple sheath material. Good high temperature strength, corrosion resistance and is resistant to chloride-ion stress corrosion, cracking and oxidation. Do not use in sulfur bearing environments.
Hastelloy X – Maximum temperature 2200F (1205C) widely used in aerospace applications. Resistant to oxidizing, reducing and neutral atmospheric conditions. Excellent high temperature strength.
Standard sheath diameters .032” +.001 -.0005" .040” +.001 -.0005” .063” ±.001” .090” ±.001” .125” +.002 -.001” .188” +.002 -.001” .250” +.003 -.001” | Suggested Upper Temperature Limits 1290°F (700°C) 1290°F (700°C) 1690°F (920°C) 1830°F (1000°C) 1960°F (1070°C) 2100°F (1150°C) 2100°F (1150°C) |
All MgO compacted thermocouples can be bent on a radius of twice the sheath diameter.
If you don't see what you are looking for here, or if you have additional questions please feel free to contact Temprel at 1-800-582-5098.
Wednesday, January 18, 2012
What is a Thermocouple?
A thermocouple is a temperature measurement device based on the Seebeck Effect. This is defined as two dissimilar metals, joined at both ends. When one end is hotter than the other, a small continuous EMF is generated. Another EMF develops along the temperature gradient of a single homogeneous wire. This is the Thompson Effect.
It is important that each section of wire in a given circuit be homogeneous, since with no change in composition, the circuit EMF depends only on the alloy and the temperature of their junctions. If both junctions are held at the same temperature, the metal does not contribute to the net EMF of the circuit. The law of intermediate metals points out that the introduction of a third metal into the circuit will have no effect upon the EMF generated as long as the junctions of the third metal with the other two alloys are at the same temperature.
In industry today, standard homogeneous alloys are employed for the various calibrations most widely used. These are types K, J, T, and E thermocouples. Others such as R, S, B, N, and W thermocouples are also used for the process and metals industries.
J 0
to 750 C +/- 1.1 C or .4% of
reading
It is important that each section of wire in a given circuit be homogeneous, since with no change in composition, the circuit EMF depends only on the alloy and the temperature of their junctions. If both junctions are held at the same temperature, the metal does not contribute to the net EMF of the circuit. The law of intermediate metals points out that the introduction of a third metal into the circuit will have no effect upon the EMF generated as long as the junctions of the third metal with the other two alloys are at the same temperature.
In industry today, standard homogeneous alloys are employed for the various calibrations most widely used. These are types K, J, T, and E thermocouples. Others such as R, S, B, N, and W thermocouples are also used for the process and metals industries.
Type Useful Range
T 0
to 350 C +/- .5 C or .4% of
reading
K 0
to 1250 C +/- 1.1 C or .4% of
reading
E 0
to 900 C +/- 1.0 C or .4% of
reading
The calibration used is not as dependant on the output as it was in the past. With the advent of the microchip, electronics can filter out noise and linearized the curve of any type thermocouple with cold junction compensation to 0 C over a broad range to allow one type to be a standard for all measurements. That is why type K thermocouple is the most often specified.
If you don't see what you are looking for here, or if you have additional questions please feel free to contact Temprel at 1-800-582-5098.
If you don't see what you are looking for here, or if you have additional questions please feel free to contact Temprel at 1-800-582-5098.
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