How to use platinum rhodium thermocouples correctly?

What are the consequences if the metal wires of two thermocouple materials come into contact in air? Firstly, we need to give a brief introduction to thermocouples. Thermocouples are actually temperature sensing elements and instruments. It directly measures temperature and converts the temperature signal into a thermoelectric potential signal, which is then converted into the temperature of the measured medium through electrical instruments (secondary instruments). Thermocouples, as measuring tools for thermal monitoring and testing, play an important role in practical applications.

In the current production process, detection technology and its tools are becoming increasingly important, especially in non-destructive scratching, measurement, and metrology of various products and components. Ceramic thermocouples play an indispensable role in improving quality and the economic benefits of enterprises.
The working principle of a thermocouple is that when two conductors with different compositions are connected at both ends to form a circuit, a thermoelectric potential will be generated in the circuit when the temperatures of the two junction points are different. If there is a temperature difference between the measuring end of the thermocouple (the end that senses the measured temperature is called the measuring end) and the participating end (the end at a known temperature is called the reference end or the cold end), the display instrument will show the temperature value corresponding to the thermoelectric potential generated by the thermocouple.

Platinum rhodium thermocouple is a traditional temperature measuring element with stable thermoelectric performance and strong oxidation resistance, suitable for continuous use in oxidizing and inert atmospheres. The long-term usage temperature is 1600 ℃, and the short-term usage temperature is 1800 ℃.
Advantages of Platinum Rhodium Thermocouples

Platinum rhodium thermocouples have the advantages of accuracy, stability, wide temperature measurement range, long service life, and high temperature measurement upper limit in the thermocouple series. Suitable for oxidizing and inert atmospheres, and can also be used in vacuum for a short period of time, but not suitable for reducing atmospheres or atmospheres containing metal or non-metal vapors. A significant advantage of B-type thermocouples is that they do not require compensation wires, as the thermoelectric potential is less than 3 μ V within the range of 0-50 ℃.

Disadvantages of Platinum Rhodium Thermocouples

The shortcomings are thermoelectric potential, low thermoelectric potential, low sensitivity reading, decreased mechanical strength at high temperatures, high sensitivity to pollution, expensive precious metal materials, and therefore high investment. The working principle of platinum rhodium thermocouple is that when two conductors with different compositions are connected at both ends to form a circuit, a thermal current will be generated in the circuit when the temperature of the two junction points is different. If there is a temperature difference between the working end and the reference end of the thermocouple, the display instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the thermocouple.

Application range of platinum rhodium thermocouple

Platinum rhodium thermocouple is actually a material that uses the characteristic that its resistance changes with temperature changes to measure temperature When there is a temperature gradient in the measured medium, the measured temperature is the average temperature in the medium where the temperature sensing element is located. The transmitter is mainly used in industrial fields such as petrochemicals, metallurgy, power food, pharmaceuticals, papermaking, and textiles to detect parameters such as differential pressure, pressure, liquid level, interface, and density of liquids. When used with throttling devices, it can be used to measure flow rate. It converts the measured signal into 4-20MaDC and transmits it to display, calculate, regulate, or control instruments, which can form various self-control systems.

Selection of Platinum Rhodium Thermocouples

When the measured temperature is normally between 1000~1300 ℃, it is recommended to use a single platinum rhodium thermocouple (platinum rhodium 10 platinum). When the measured temperature is normally between 1200~1600 ℃, it is recommended to use a dual platinum rhodium thermocouple (platinum rhodium 30 platinum rhodium 6). This ensures the service life of the platinum rhodium thermocouple within the temperature range used.

The thermoelectric potential of a thermocouple will increase as the temperature at the measuring end rises. The magnitude of thermoelectric potential is only related to the material of the thermocouple conductor and the temperature difference at both ends, and is independent of the length and diameter of the thermoelectric electrode.

Proper use of thermocouples can not only accurately obtain temperature values and ensure product quality, but also save material consumption of thermocouples, which not only saves money but also ensures product quality. Incorrect installation, thermal conductivity, and time lag are the main errors in the use of thermocouples.