Environmental Instruments specializes in the production of various types of pressure transmitters, temperature transmitters, temperature sensors, liquid level transmitters and related accessories. The product has received support from the National Science and Technology Commission from design, development to success. The National Science and Technology Commission invested more than 6 million yuan and invited internal experts and academicians of the Russian Academy of Sciences to jointly develop the product. After that, the company itself continued to update and improve, and developed a series of pressure transmitters, temperature transmitters and liquid level transmitters that are stable, reliable, cheap and high-quality, suitable for various industrial automation measurement and control, and became a professional transmitter manufacturer.
Recently, many friends have asked about the difference between temperature transmitters and temperature sensors. Today we will talk about the differences between thermocouples and thermal resistors in temperature transmitters!
Advantages of thermocouples in temperature transmitters:
Thermocouples are one of the most commonly used temperature detection components in industry. The working principle of thermocouples is based on the Seeback effect, which is a physical phenomenon in which two conductors of different compositions are connected at both ends to form a loop. If the temperatures of the two connecting ends are different, a thermal current will be generated in the loop. The advantages are:
①High measurement accuracy. Because the thermocouple is in direct contact with the measured object, it is not affected by the intermediate medium.
②Wide measuring range. Commonly used thermocouples can continuously measure from -50 to +1600°C. Some special thermocouples can measure as low as -269°C (such as gold, iron, nickel and chromium) and as high as +2800°C (such as tungsten-rhenium).
③Simple structure and easy to use. Thermocouples are usually composed of two different metal wires, and are not limited by size or opening. They have protective sleeves on the outside, making them very convenient to use.
Temperature compensation of thermocouple cold junction:
Since the materials of thermocouples are generally relatively expensive (especially when precious metals are used), and the distance between the temperature measurement point and the instrument is very long, in order to save thermocouple materials and reduce costs, compensation wires are usually used to extend the cold end (free end) of the thermocouple to the control room where the temperature is relatively stable, and connect it to the instrument terminals. It must be pointed out that the thermocouple compensation wire only functions to extend the hot electrode and move the cold end of the thermocouple to the instrument terminal in the control room. It itself cannot eliminate the influence of the cold end temperature change on the temperature measurement and has no compensation effect. Therefore, other correction methods need to be used to compensate for the impact on temperature measurement when the cold end temperature t0≠0℃.
When using the thermocouple compensation wire, you must pay attention to the matching model, the polarity cannot be wrong, and the temperature of the compensation wire and the thermocouple connection end cannot exceed 100°C.
Thermal resistance
Thermal resistance is the most commonly used temperature detector in medium and low temperature areas. Its main features are high measurement accuracy and stable performance. Among them, platinum thermal resistance has the highest measurement accuracy. It is not only widely used in industrial temperature measurement, but also made into a standard benchmark instrument.
Thermal resistance temperature measurement principle and materials:
Thermal resistance temperature measurement is based on the characteristic that the resistance value of a metal conductor increases as the temperature increases. Thermal resistors are mostly made of pure metal materials. Currently, platinum and copper are the most widely used. In addition, thermal resistors have begun to be made of materials such as nickel, manganese and rhodium.
Regarding the temperature transmitter, you can take a look at the following introduction:
1. Purpose of temperature transmitter
Temperature transmitter is used for temperature measurement. This article defines a temperature transmitter as a temperature measurement device that uses a temperature sensor for temperature detection and converts the signal of the temperature sensor into a standard current signal and a standard voltage signal through a conversion circuit.
2. Classification of temperature transmitters
From the signal output interface, it is divided into 4~20ma, 0~10ma, 0~20ma, 0~5v, 0~10v, etc., or digital/frequency interface and other interfaces;
From the structure and installation form, it is divided into wall-mounted type, air duct type, and probe type;
From the distance between the temperature sensor and the conversion circuit, it is divided into integrated or split type;
There are also explosion-proof and other types of products.
The above is about the difference between temperature transmitter and temperature sensor. For more information about instruments, please pay attention to Environmental Instruments. If you have any selection questions, you can also call us directly.