Sheathed thermocouple have the advantages of bending, high pressure resistance, fast thermal response time and durability.

Advantages

1. Less thermal response time,which can reduce the dynamic error.
2. Flexible mounting for use.
3. Wide measuring scope.
4. High mechanical strength and good pressure resistance.

There are actually many techniques for using sheathed thermocouples.

• It has bendable performance. The thermal resistance of the sheath can be bent in any direction . except for the head, so it is suitable for the temperature of the complicated structure and small equipment.
• The sheathed thermocouple has good vibration and impact resistance. Therefore, its life is longer than ordinary thermal resistance.
• The sheathed thermocouple has a long service life. Because the resistance body of the sheathed thermal resistance is maintained by the metal sleeve, the thermal resistance wire is not easily corroded by harmful media.
• It is suitable for measuring in strong alkali and corrosive medium. with a temperature resistance of 250℃, and the fixed installation situation can also use the same PTFE fixed thread.
• According to the measurement temperature range and side measurement object, select the appropriate thermal resistance model, specification and maintenance tube information.

What Is Sheathed Thermocouple?

Sheathed thermocouples consist of an outer metallic sheath, which contains the insulated internal leads, embedded within a high-density ceramic compound (mineral-insulated cable, also called MI cable). Sheathed thermocouples are bendable and may be bent to a minimum radius of five times the sheath diameter.

Learn more about Thermocouple from Wikipedia.

What Are The Types Of Sheathed Thermocouple?

Sheathed thermocouples have different types. Type J, K, T, & E are “Base Metal” thermocouples, the most common types of thermocouples. Type R, S, and B are “Noble Metal” thermocouples, which are used in high temperature applications (see thermocouple temperature ranges for details)

Model	Graduation	Range of temperature  measurement ℃ —–I	Tolerance value—-I	Range of temperature measurement ℃—II	Tolerance value—-II
WRNK	K	-40~+375	±1.5℃	-40~+333	±2.5℃
WRNK	K	375~1000	±0.004ltl	333~1200	±0.0075ltl
WRNK	N	-40~+375	±1.5℃	-40~+333	±2.5℃
WRNK	N	375~1000	±0.004ltl	333~1200	±0.0075ltl
WRNK	E	-40~+375	±1.5℃	-40~+333	±2.5℃
WRNK	E	375~800	±0.004ltl	333~900	±0.0075ltl
WRNK	J	-40~+375	±1.5℃	-40~+333	±2.5℃
WRNK	J	375~750	±0.004ltl	333~750	±0.0075ltl
WRNK	T	-40~+125	±0.5℃	’-40~133	±1.0℃
WRNK	T	125~350	±0.004ltl	133~350	±0.0075ltl
WRNK	S	0~+1100	±1.0℃	0~600	±1.5℃
WRNK	S	1100~1600	±[1+0.003(t-1100)]	600~1600	±0.0025ltl
WRNK	R	0~1000	±1.0℃	0~600	±1.5℃
WRNK	R	1100~1600	±[1+0.003(t-1100)]	600~1600	±0.0025ltl
WRNK	B	——	——	600~1700	±0.0025ltl
WRNK	B	——	——	——	—

Extended reading:  Tri Clamp Sanitary Thermometers

Can You Overheat a Sheathed Thermocouple?

• In terms of the sheath thermocouple, the environment temperature is 20 + 15℃, the relative humidity is not more than 80%, the test voltage is 500 + 50V(DC), the insulation resistance between electrode and outer sleeve≥1000MΩ.m.
• That is to say, the insulation resistance for sample of 1m is 1000MΩ;
• the insulation resistance for sample of 10m is 100MΩ.

Sheathed Thermocouple’s Working Principle

The electrode of sheath thermocouple are consisted by two different materials of conductor. When there is a temperature difference between the measuring end and the reference end, it will generate the thermal electric potential. The working instrument will show the corresponding temperature value of the thermal electric potential.

How Do You Identify A Sheathed Thermocouple?

If the flame ignites and goes out when you release the gas control knob after holding it in for the recommended 20 to 30 seconds, that’s the sign of a thermocouple malfunction. Before jumping to the conclusion that the thermocouple is at fault, look at the pilot flame.

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