Thermocouple Wire
Thermocouple wires are materials used for measuring temperature, utilizing the thermoelectric voltage which varies with temperature difference. These alloys feature high thermoelectric potential, a linear relationship between temperature and voltage, long-term stability, good uniformity, and excellent oxidation resistance, making them widely used in defense, research, metallurgy, chemical industries, and temperature sensing elements.
The K-type thermocouple, consisting of nickel-chromium (NiCr) and nickel-silicon (NiSi), is the most commonly used thermocouple in temperature ranges above 500°C. Its positive pole (KP) has a nominal composition of Ni:Cr≈90:10, and the negative pole (KN) has a composition of Ni:Si≈97:3. The temperature range is -200°C to 1300°C, suitable for oxidative and inert atmospheres. However, K-type thermocouples should not be used directly in high temperatures under sulfur, reducing, or alternating reduction-oxidation conditions, or in vacuum environments, and are not recommended for weakly oxidative atmospheres.
| Diameter/mm | Long-term Operating Temperature | Short-term Operating Temperature |
| temperature/°C | temperature/°C | |
| 0.3 | 700 | 800 |
| 0.5 | 800 | 900 |
| 0.8,1.0 | 900 | 1000 |
| 1.2,1.6 | 1000 | 1100 |
| 2.0,2.5 | 1100 | 1200 |
| 3.2 | 1200 | 1300 |
J-Type Thermocouples are suitable for use in vacuum, nitriding, oxidizing, reducing, and inert atmospheres, but the positive electrode (iron) oxidizes quickly at high temperatures. Therefore, the operating temperature is limited, and they cannot be used directly without protection at high temperatures above 500°C in oxidizing atmospheres.
| Diameter /mm | Long-term Operation | Short-term Operation |
| °C | °C | |
| 0.3 ,0.5 | 300 | 400 |
| 0.8, 1.0, 1.2 | 400 | 500 |
| 1.6, 2.0 | 500 | 600 |
| 2.5, 3.2 | 600 | 750 |
E-Type thermocouples are less sensitive to corrosion in high-humidity atmospheres and are suitable for environments with high humidity. E-Type thermocouples also have good stability, better oxidation resistance than copper-constantan and iron-constantan thermocouples, and are more cost-effective. Suitable for use in oxidizing and inert atmospheres, widely adopted by users.
E-Type Thermocouples cannot be used directly at high temperatures in sulfur or reducing atmospheres because of its poor thermoelectric uniformity.
| Thermocouple Wire, -200~900 ℃(for short term) and 0~750℃( for long term) Compensation Wire, 32 to 392F (0 to 200℃) | ||
| Diameter/mm | Long-term Operating Temperature | Short-term Operating Temperature |
| 0.3, 0.5 | 350 | 450 |
| 0.8, 1.0,1.2 | 450 | 550 |
| 1.6,2.0 | 550 | 650 |
| 2.5 | 650 | 750 |
| 3.2 | 750 | 900 |
It has advantages such as good linearity, high thermoelectric voltage, high sensitivity, good stability and uniformity, and is cost-effective. Particularly used in the -200 to 0°C temperature range, with better stability, annual stability can be less than ±3μV. It can be used for low-temperature calibration as a second-class standard for low-temperature value transfer.
T-type thermocouple has poor oxidation resistance at high temperatures, limiting its maximum operating temperature.
| Short-term | -40~750 ℃ |
| Long-term | 0~600℃ |
| Compensation Wire | 32 to 392F (0 to 200℃) |
Nickel-Chromium-Silicon or Nickel-Silicon-Magnesium Thermocouple (N-Type Thermocouple) is a low-cost metal thermocouple and the latest internationally standardized thermocouple. Its overall performance is superior to the K-type thermocouple. The N-type thermocouple should not be directly used in high-temperature sulfur, reducing, or cyclic reducing-oxidizing atmospheres and in a vacuum. It is also not recommended for weak oxidizing atmospheres.
- The nominal chemical composition of the positive electrode (NP) is: Ni:Cr:Si ≈ 84.4:14.2:1.4
- The nominal chemical composition of the negative electrode (NN) is: Ni:Si:Mg ≈ 95.5:4.4:0.1
- The temperature range for use is -200 to 1300°C.
Platinum-Rhodium wire is a binary alloy of platinum containing rhodium, which forms a continuous solid solution at high temperatures. Platinum-Rhodium wire in the thermocouple series has high accuracy, excellent stability, a wide temperature measurement range, long service life, and high maximum temperature measurement capabilities. Suitable for use in oxidizing and inert atmospheres, it can also be used short-term in a vacuum, but is not suitable for reducing atmospheres or atmospheres containing metallic or non-metallic vapors.
- Platinum Rhodium-10% Platinum
R-type thermocouple wire is a high-precision temperature measurement solution used in industrial and laboratory applications requiring extreme accuracy and stability. This thermocouple type is composed of platinum (Pt) and rhodium (Rh) alloys, making it highly resistant to oxidation and suitable for high-temperature environments.
- Platinum Rhodium-13% Platinum
The B-type thermocouple is a platinum-rhodium thermocouple, also known as a high-temperature precious metal thermocouple. These are widely used as temperature sensors, typically in conjunction with temperature transmitters, controllers, and display instruments. Together, they form a process control system used for the direct measurement or control of temperatures in various production processes within the temperature range of 0–1800°C. The B-type thermocouple uses high-purity platinum for the negative electrode and a platinum-rhodium alloy for the positive electrode.
| Thermocouple Type | Material | Temperature Range | Sensitivity @ | Error* | App.** |
| ( & -) | Range°C | 25°C (77°F) | |||
| (°F) | µV/°C | ||||
| (µV/°F) | |||||
| B | 70％platinum/ 30％rhodium | -50~1750 | 6 | LT:±2.8°C (±5°F) | I,O |
| 94％platinum/ 6％rhodium | (-60~3200) | -3.3 | HT:±0.5% |
- Provides accurate temperature readings, suitable for environments requiring precise measurements
- Can operate across a broad temperature range, adaptable to various environmental conditions
- Reacts swiftly to temperature changes, ensuring real-time monitoring
- Industrial processes: Monitoring the temperature in furnaces, kilns, and reactors
- Aerospace: Measuring high-temperature parts such as jet engines
- Automotive: Engine testing and exhaust system monitoring
- HVAC systems: Temperature regulation and control
- Medical and laboratory: Low-temperature applications, sterilization, and research experiments
