Platinum-rhodium thermocouple

1.What is a Platinum-rhodium thermocouple?

The platinum-rhodium thermocouple is a high-temperature Temperature Sensor based on the Seebeck effect, composed of positive and negative electrodes made of platinum (Pt) and rhodium (Rh) alloys. Its stability and high-temperature resistance make it the preferred equipment for industrial high-temperature measurement, and it is widely used in metallurgy, chemical engineering, glass manufacturing and other fields.

 

2. Working Principle of Platinum-Rhodium Thermocouples

Platinum-rhodium thermocouples operate based on the thermoelectric effect: when there is a temperature difference at both ends of a closed circuit composed of two different metals, an electromotive force (EMF) will be generated in the circuit. By measuring this EMF, the temperature value can be calculated.

·Features

High precision: The error is less than ±1℃ within the range of 0 to 1600℃.

Strong stability: It can still maintain high precision after long-term use.

Corrosion resistance: Suitable for oxidizing or inert atmosphere environments.

 

3. Common Types of Platinum-Rhodium Thermocouples

·Type S (Platinum-rhodium 10-platinum)

Positive electrode: Platinum-rhodium 10 alloy (containing 10% rhodium)

Negative electrode: Pure platinum

Range: 0-1600℃ (Short-term up to 1700℃)

Application: Precise temperature measurement in laboratories, high-temperature heat treatment.

 

·Type R (Platinum-rhodium 13-platinum)

Positive electrode: Platinum-rhodium 13 alloy

Negative electrode: Pure platinum

Range: 0 to 1600℃

Features: It has a higher output electromotive force than the S-type and is suitable for higher-precision scenarios.

 

·Type B (Platinum-rhodium 30- Platinum-rhodium 6)

Positive electrode: Platinum-rhodium 30 alloy

Negative electrode: Platinum-rhodium 6 alloy

Range: 200-1800℃

Advantages: Strong anti-pollution ability, long service life, suitable for long-term high-temperature environments.

 

4. Application Fields of Platinum-Rhodium Thermocouples

Steel and metallurgy: Used for steel water temperature detection and monitoring of blast furnace hot blast stoves.

Glass industry: Temperature measurement of molten glass liquid to ensure molding quality.

Chemical industry: Temperature control for high-temperature equipment such as reaction vessels and cracking furnaces.

Aerospace: Temperature monitoring of engine combustion chambers and turbine inlets.

 

5.Precautions for Use and Maintenance Suggestions

Installation specifications

Avoid mechanical stress or frequent bending to prevent electrode breakage.

Ensure that the thermocouple is in full contact with the measured medium to reduce thermal conduction errors.

Environmental adaptability

It performs best in an oxidizing atmosphere. A protective tube needs to be installed in a reducing atmosphere (such as CO, H₂).

Avoid long-term use in an environment containing corrosive gases such as phosphorus and sulfur.

 

Regular calibration

After long-term use in high-temperature environments, errors need to be corrected through fixed-point calibration (such as palladium points, platinum points).

 

Common Fault Handling

Abnormal output signal: Check for damage to the wire connection or insulation layer.

Shortened lifespan: It may be caused by high-temperature volatilization or grain coarsening. It is recommended to use Type B thermocouples.

 

6. Selection Guide for Platinum-Rhodium Thermocouples

Model applicable temperature advantages recommended scenarios

S-type 0~1600℃ high-precision laboratory, scientific research

R-type high-precision industrial furnace with strong signal from 0 to 1600℃

Type B has a long service life ranging from 200 to 1800℃ and is suitable for long-term high-temperature working conditions

7. Summary

Platinum-rhodium thermocouples, with their high stability and precision, occupy an irreplaceable position in the field of high-temperature measurement. Correct selection, standardized installation and regular maintenance are the keys to ensuring its long-term reliable operation. In the future, with the advancement of material technology, the temperature resistance limit and service life of platinum-rhodium thermocouples will be further enhanced.