Type S Thermocouple – Rhodium Thermocouple

The Type S thermocouple (Model WRP-130) is a high-temperature platinum-rhodium thermocouple. Classified under the “S” graduation, it is primarily used to measure temperatures ranging from 0°C to 1600°C and belongs to the category of noble metal thermocouples.

Type S thermocouples are typically used in conjunction with display instruments, recorders, and electronic regulators. They can directly measure the temperatures of liquids, vapors, and gases—as well as solid surfaces—within a range of 0°C to 1800°C across various industrial processes. They are commonly employed in high-temperature environments such as industrial furnaces, coking plants, and steel mills. Featuring a 99.7% high-purity alumina protection tube, the unit delivers reliable performance and electrical insulation even in harsh thermal conditions.

RFQ

Features

Disadvantages of S Type Thermocouples:

• Low thermoelectric output and sensitivity; reduced mechanical strength at high temperatures.
• Highly sensitive to contamination; expensive noble metal materials result in a high initial investment.

Technical Specifications for Type S Thermocouples

1. Specifications are based on standard production. Custom lengths, diameters, and connection types are available upon request.
2. The usable temperature range depends on the process atmosphere, installation method, and application conditions.
3. Do not use alumina ceramic tubes in reducing atmospheres (H2 or CO) above 1400 °C.
4. Cold-junction compensation is required for accurate temperature measurement.
5. Handle carefully. Ceramic protection tubes are brittle and may fail under thermal shock if not properly preheated or acclimated.

Working Principle

A thermocouple is a temperature sensor based on the Seebeck Effect. Its core mechanism is as follows:

Seebeck Effect: When two dissimilar conductors or semiconductors (e.g., metals A and B) form a closed circuit and a temperature difference exists between the two junctions, an electromotive force (thermoelectric potential) is generated within the circuit. This phenomenon was discovered by the German scientist Thomas Johann Seebeck in 1821.

Structural Components:

• Thermo-electrodes: Composed of conductors or semiconductors made from two different materials (e.g., Nickel-Chromium/Nickel-Silicon, Platinum-Rhodium/Platinum, etc.).
• Measuring Junction (Hot Junction): Placed in the temperature field being measured; typically at a higher temperature.
• Reference Junction (Cold Junction): Usually placed in an environment with a known temperature (e.g., a 0°C ice bath or extended to room temperature via compensation wires).

Temperature Measurement:

By measuring the magnitude of the thermoelectric potential and accounting for the cold junction temperature (requiring cold junction compensation or calculation-based correction), the hot junction temperature can be determined. The relationship between thermoelectric potential and temperature is defined by the thermocouple’s calibration table (graduation table); different material combinations correspond to different calibration standards.

Type S Thermocouple Reference Table (°C)

Thermoelectric voltage in millivolts (mV), reference junction at 0 °C. Values per NIST ITS-90 (NIST Monograph 175) / IEC 60584-1. Range: −50 °C to 1768 °C.

How to read: row + column = temperature. Example: 1000 °C row, column 5 → 1005 °C = 9.645 mV. For negative rows, temperature = row − column (e.g., −40 row, column −5 → −45 °C).

Applications

• Metallurgical Industry: Monitoring temperatures in smelting furnaces, forging equipment, and heat treatment furnaces to ensure precise temperature control during metal processing.
• Chemical Industry: Monitoring temperatures in chemical reactors, distillation columns, and storage tanks to ensure the smooth progression of chemical reactions.
• Power Industry: Monitoring temperatures in boilers, steam turbines, and generators to ensure safe equipment operation and efficiency.
• Automotive Industry: Monitoring temperatures in engines, exhaust systems, and batteries to ensure vehicle performance and safety.
• Aerospace: Monitoring temperatures of aircraft engines and rocket launch components under extreme conditions to ensure system reliability.

Order Guide

When ordering Type S thermocouples, please confirm the following parameters:

1. Medium to be measured
2. Temperature range
3. Thermocouple model and calibration type (graduation mark)
4. Number of thermocouple points
5. Material, diameter, and length of the thermocouple protection tube, etc.
6. Relevant dimensions for fasteners or flange fittings (if applicable)
7. Requirements for the electrical connection head (terminal box)

More Temperature Measurement Solutions

Sino-Inst manufactures thermocouples—including Platinum-Rhodium 30 vs. Platinum-Rhodium 6, Platinum-Rhodium 10 vs. Platinum, NiCr vs. NiSi, NiCr vs. CuNi, Cu vs. CuNi, and Fe vs. CuNi types—that comply with IEC standards for graduation numbers. Our temperature sensors are produced using rigorous, established manufacturing processes, ensuring excellent internal quality. Please feel free to contact our sales engineers to confirm specifications for custom S-type thermocouples.

Zhang Wei

Zhang Wei, possesses 20 years of experience as an automation instrumentation engineer, specializing in the research, design, installation, commissioning, and maintenance of automation instruments.

Face to various instrument communication protocols (such as Modbus, Profibus, etc.), with solid hardware circuit design and software programming skills (proficient in C language and PLC programming). Has extensive project experience; projects he has led and participated in have all achieved outstanding results, improving product accuracy, reducing costs, and increasing production efficiency.

Possesses excellent communication and coordination skills and a strong team spirit, enabling him to quickly respond to customer needs and provide high-quality automation instrumentation solutions.