Fe-CuNi Type J Constantan Thermocouple Wire Fast-Responding And Stable For Industry

Fe-CuNi (Type J) Thermocouple Wire, also known as Iron-Constantan Thermocouple Wire, is a widely used thermocouple type for temperature measurement. The thermocouple is made of two different metal alloys: iron (Fe) for the positive leg and copper-nickel (CuNi), commonly called constantan, for the negative leg. Type J thermocouples are known for their reliability, affordability, and versatility across a wide range of industrial and scientific applications.

Type J Fe-CuNi thermocouple wire is a popular, cost-effective, and reliable option for measuring moderate temperatures. It is particularly useful in industrial processes, laboratory measurements, and general-purpose temperature sensing where high sensitivity and accuracy in the mid-range temperature zone are important. However, for applications involving temperatures over 750°C or environments prone to heavy oxidation, other thermocouple types (e.g., Type K, Type N) may be preferred.

color codes of thermocouple ( J type )

The operating temperature range of type J thermocouple is -210~1200℃ , but it is usually used in the temperature range 0~750℃ due to embrittlement of Iron.

Type J thermocouple has good resistance to oxidation and high EMF output against Platinum 67, with good temperature accuracy, sensitivity and stability. It is recommended for vacuum, oxidizing, reducing or inert atmospheres, but it can not be used in sulphurous atmosphere above 500℃ .

Thermocouple temperature range and tolerance

Some Key Features Fe-CuNi (Type J) Constantan Thermocouple Wire include:

1. Composition:

• Positive Leg (Fe): Made of iron (Fe). Iron is a relatively low-cost material but prone to oxidation at high temperatures, which can affect the accuracy at higher temperatures.
• Negative Leg (CuNi or Constantan): Made of a copper-nickel alloy (Constantan), which provides good stability and resistance to oxidation.

2. Temperature Range:

• Type J thermocouples can measure temperatures in the range of -40°C to 750°C (-40°F to 1382°F). They are particularly useful for applications where moderate to high temperatures are encountered, but not as suitable for extreme conditions like those handled by Type K or Type S thermocouples.
• They perform well in the lower to mid-range temperatures compared to other thermocouple types.

3. Voltage Output:

• Voltage per °C (Seebeck coefficient): The output voltage generated by a Type J thermocouple is approximately 69 µV/°C at 0°C to 100°C (higher than some other types, such as Type K). This means that Type J thermocouples offer a relatively high sensitivity, which leads to more precise readings in low-temperature ranges.
• This high voltage output improves the resolution of measurements, making it useful for applications requiring high precision.

4. Accuracy:

• The accuracy of Type J thermocouples is typically ±2.2°C or ±0.75% of the temperature, which makes it suitable for general-purpose temperature measurements.
• The accuracy of Type J thermocouples is generally sufficient for industrial and laboratory settings, though it may not offer the ultra-high precision of Type E or Type S thermocouples.

5. Linear Response:

• The relationship between the voltage output and temperature is relatively linear for Type J thermocouples, especially within the lower to mid-range temperatures (up to about 750°C).
• This linear response makes it easier to calibrate and interpret measurements accurately.

6. Corrosion Resistance and Durability:

• Constantan (CuNi alloy) provides good resistance to oxidation and corrosion, which is one of the reasons for its popularity in industrial applications.
• However, iron is susceptible to oxidation at high temperatures (above 600°C), which can affect the accuracy of readings. As a result, Type J thermocouples are better suited for lower-to-medium temperature environments.

7. Cost-Effective:

• Type J thermocouples are generally more affordable than many other types, such as Type S or Type R thermocouples. This makes them a cost-effective choice for applications where precision and reliability are important but budget constraints exist.

Applications:

• ndustrial Applications: Widely used in processes such as heat treatment, furnace temperature monitoring, and chemical processing.
• Laboratories: Commonly used for general-purpose temperature measurements in laboratory settings, particularly when lower-cost sensors are needed.
• Food and Beverage Industry: Used for temperature monitoring in food processing and storage, especially when temperatures are below 500°C.
• OEM Applications: Employed in manufacturing and automated systems for monitoring ambient and operating temperatures.
• Vacuum Applications: Suitable for use in vacuum chambers, especially in the mid-range temperature zone (up to 750°C).

​Pros of Fe-CuNi (Type J) Thermocouples:

• High Sensitivity: Type J thermocouples offer relatively high sensitivity compared to other types, especially in the lower temperature ranges.
• Good Linear Output: They produce a linear voltage-to-temperature relationship, which simplifies calibration and reduces measurement error.
• Cost-Effective: They are an affordable solution for general-purpose temperature measurements.
• Reliability: They are durable and offer reliable performance in moderate-temperature ranges.

Cons of Fe-CuNi (Type J) Thermocouples:

• Susceptibility to Oxidation: The iron leg of the thermocouple is prone to oxidation, particularly at temperatures over 600°C, which can compromise the accuracy and reliability of measurements.
• Limited High-Temperature Range: While they can measure up to 750°C, they are not suitable for extreme temperature ranges compared to thermocouples like Type K or Type R.