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Introduction to Several Commonly Used Temperature Sensors 1. Overview Over the past century or so, temperature instruments have developed to feature characteristics such as casing design, armored construction, integration, and compactness. At the same time, to meet the temperature measurement requirements in certain special environments, products have made significant progress in terms of corrosion resistance, wear resistance, high-temperature resistance, and high-pressure resistance in recent years. Based on the current situation, when addressing the issues of contact temperature measurement in such special environments, efforts are generally made in aspects such as the design of protective sleeves, material selection, and surface coating technologies. 2. Common types of temperature instruments 2.1 Assembled thermocouples 2.2 Assembled thermal resistors 2.3 Encased thermocouples 2.4 Encased thermal resistors 2.5 Wear-resistant thermocouples/resistors 2.6 Multi-point thermocouples/resistors 2.7 Pneumatic thermocouples 2.8 High-temperature and high-pressure thermocouples 2.9 Bimetallic thermometers 2.10 Integrated temperature transmitters 2.1 WR₰ series assembled thermocouples B. Main technical parameters: a) Temperature measurement range and tolerance: 2.1 WR₰ series assembled thermocouples b) Thermal response time τ0.5: 2.2 WZ₰ series assembled thermal resistors A. Main features: ★ High measurement accuracy. ★ Complete range of specifications. ★ It features stable and reliable performance. ★ It is easy to install and use. ★ It’s cheap. ★ Poor seismic performance. 2.2 WZ₀ series assembled thermal resistors B, main technical parameters: a) Temperature measurement range and tolerance: 2.2 WZ₀ series assembled thermal resistors b) Thermal response time τ0.5: Schematic diagrams of products in various structural forms for WR₀ series assembled thermocouples and WZ₀ series assembled thermal resistors; Typical installation methods for WR₀ series assembled thermocouples and WZ₀ series assembled thermal resistors 2.3 WR₀K and WRG₀K series armored thermocouples A, main features: ☆ Slender shape. Diameters ranging from φ0.25mm to φ12.7mm, etc ； ☆Fast thermal response time. The thermal response time τ0.5 ranges from a minimum of 0.1 S to a maximum of 8 S ； ☆High measurement accuracy. The product accuracy fully meets the requirements of the IEC584-2 standard ； ☆The product range is comprehensive. There are eight standard types of thermocouples: K, N, E, J, T, S, R, and B. ☆High reliability, vibration resistance, and long service life. The insulator has high purity and filling density, resulting in good mechanical strength for the product. ☆Easy to install and can be bent freely. The minimum bending radius is 5 times the product’s diameter ； ☆The junction box features a high protection rating, a large wiring compartment, and easy wiring. The protection rating can reach IP65 ； ☆Wide measurement range. -200°C to 1300°C. 2.3 Schematic diagram of the main structure of WR₰K and WRG₰K series armored thermocouples B: 2.3 WR₰K and WRG₰K series armored thermocouples C, Main technical specifications 1. Temperature measurement range: 2.3 WR₰K and WRG₰K series armored thermocouples C, Main technical specifications 3. Thermal response time: 4. Insulation resistance at room temperature: 2.4 Main features of WZPK and WZGPK series armored thermal resistors A: ☆ Slender shape. ☆Fast thermal response time. ☆High measurement accuracy. ☆High reliability, vibration resistance, and long service life. ☆Easy to install and can be bent freely. ☆The wiring compartment of the junction box has ample space, making wiring convenient. ☆The product has a high protection rating, reaching IP65. 2.4 Schematic diagram of the main structure of the armored thermoresistors of the WZPK and WZGPK series: 2.4 C. Main technical specifications of the armored thermoresistors of the WZPK and WZGPK series; 2.4 D. Schematic diagram of the structure of the measurement terminal. 1. Classified by the method of processing the protective tube: there are two types – integral drilling type and welded type ； 2. Classified by the structural type of the protective tube: conical and straight types ； 3. Classified by process interface method: there are three types – threaded connection, flanged connection, and welding. Schematic diagram of the installation structure for armored thermocouples/resistors. Temperature sensor. 2.5 Wear-resistant thermocouples/resistors – Typical structural diagram. Key features: Application areas: Resistance to wear; used in petroleum cracking processes. Resistance to vibration; used in catalytic cracking processes. Resistance to erosion; used in cement kilns. Resistance to high temperatures and high pressures. Leak prevention. Methods of wear resistance enhancement: Spray welding, cladding, or direct use of high-temperature wear-resistant cemented carbides (such as our company’s proprietary CYT101, CYT102, CYT103, CYT104, and CYT105). 2.5 Wear-resistant thermocouples/resistors – Schematic diagram of main structural types; Temperature sensors. 2.6 Multi-point thermocouples/resistors: A. Multi-point flameproof armored thermocouples/resistors – Key features: Application areas: ★Fast response time; ★Synthesis towers; ★High precision; ★Reaction tanks; ★Vibration resistance; ★Pipelines; ★Corrosion resistance; ★Large number of measurement points. Available options: ★Armored thermocouples: 4–12 points, up to 30 m in length ； ★Encapsulated thermoresistors: 3–8 points, up to 8 m in length. Temperature sensor 2.6 Multi-point thermocouple/resistance B, Armored multi-point thermocouple (single-layer metal protective sleeve). Key features: Fast response, high accuracy, vibration resistance, corrosion resistance, easy installation; can be used in explosion-proof versions. Application areas: Synthetic towers, reaction vessels, pipelines. Temperature sensor 2.6 Multi-point thermocouple/resistance C, Multi-point armored thermocouple. Temperature sensor 2.6 Multi-point thermocouple/resistance D, Multi-point thermocouple/resistance. Schematic diagram of the main structure. 2.7 Blowing thermocouple. 1. Purpose: Used in synthetic ammonia production plants with an annual output of 300,000 tons. 2. Structural principle: A certain gas path is formed between the temperature-sensing element of the armored thermocouple and the outer protective tube. An inert gas at a specified pressure is introduced into this gas path to prevent and reduce the infiltration of reducing gases under high-temperature and high-pressure conditions, which could otherwise affect the service life of the thermocouple. 3. Key features: A rare metal called “tantalum” is incorporated into the armored thermocouple. The addition of tantalum **reduces the corrosion of the thermocouple wires by reducing gases**, thereby **extending the service life of the thermocouple**. 4. Measurement range: 800～1100℃. 5. Measurement accuracy: Grade 1 or Grade 2. 6. Blowing pressure: greater than 1.03X 105 Pa. 2.8 High-temperature and high-pressure thermocouples 1. Applications: Mainly used for temperature measurement in hydrogenation units of oil refining plants, catalytic cracking units, and pipelines. 2. Structural features: It uses a WRG K—5 N type spring-pressed armored thermocouple as the temperature sensing element, along with double-sided welded flanges and a protective sleeve featuring an integral drilling structure. 3. Key quality control points: ★Accuracy and insulation resistance testing of armored thermocouples ； ★Quality of flange forgings ； ★Radiographic inspection of the quality of protective sleeve forgings and those after machining, in two mutually perpendicular directions. 4. Measurement range: Type K and Type N: -40～800℃; Type E: -40～600℃. 5. Measurement accuracy: Grade 1 or Grade 2. 6. Maximum operating pressure: 29.4 MPa. When the temperature is between 200 and 800°C, the pressure-bearing capacity decreases. 2.9 Bimetallic Thermometer 1. Main features: ★Direct temperature display on-site, intuitive and convenient ； ★Robust structure, resistant to vibration, and not prone to damage ； ★Adjustable angle ； ★Corrosion resistance ； ★No mercury pollution ； ★Remote temperature control can be achieved. 2. Product types: ★Axial type ★Radial type ★Adjustable-angle type ★Electrical-contact type ★Integrated type. 2.9 Bimetallic thermometer. 2.9 Bimetallic thermometer. 2.9 Bimetallic thermometer – Installation diagram. 2.10 Integrated temperature transmitter. 1. Main features: Uses a two-wire transmission system, provides a large signal output of 4-20mA, has strong resistance to interference, and allows for a long transmission distance. 2. Product types: Integrated installation / Separate installation. Available with analog dials, digital displays, and HART protocol support. Temperature sensors. Part three: Corrosion prevention for temperature measuring instruments. To address the issue of corrosion in temperature measuring instruments, our factory currently employs two main measures. One is to spray or coat a polytetrafluoroethylene protective layer outside the metal protective tube. Second, use corrosion-resistant metal sleeves directly. Common materials include: aluminum, red copper, brass, titanium, 316L, tantalum, Hastelloy, 0Cr18Ni9Ti, etc. The specific material to be used depends on the type, temperature, and concentration of the medium being measured. Normally, the design institute selects it during the design process. The table below shows the applicable scenarios for several common materials: