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In a PT100 thermal resistor, the PT stands for \"platinum\", and 100 refers to the fact that its resistance is exactly 100 ohms at 0 degrees Celsius; therefore, it is commonly referred to as a PT100 thermal resistor or platinum resistor. It is one of the most widely used temperature measurement devices in medium and low temperature ranges. Thermistor temperature measurement is based on the property that the resistance value of platinum resistive elements increases proportionally as the temperature rises; when this resistance value changes, secondary instruments such as digital displays and recorders show the temperature corresponding to that resistance value. Its main features are high measurement accuracy and stable performance. Among them, platinum thermoresistors offer the highest measurement accuracy; they are not only widely used in industrial temperature measurement but also made into standard reference instruments. The relationship between the resistance value of PT100 and temperature is as follows: at a temperature of 0°C, the resistance of the PT100 resistor is 100 ohms, while at 100°C its resistance is approximately 138.5 ohms. The resistance value of a thermistor and the temperature can generally be expressed using the following approximate formula: Rt = Rt0 [1 + α (t – t0)], where Rt is the resistance value at temperature t ； Rt0 is the resistance value corresponding to temperature t0 (usually t0=0℃) ； α is the temperature coefficient. PT100 thermistors are generally suitable for temperature measurement in the range of -200 to 600°C. They feature accurate measurement, good stability, and reliable performance, making them widely used in engineering control systems. In fact, considering the variation of resistance with temperature, most metal conductors possess this property; however, not all of them can be used as temperature-sensing resistors. Metal materials used as thermal resistors are generally required to have a large and stable temperature coefficient, a high resistivity (to reduce the size of the sensor while maintaining the same sensitivity), stable chemical and physical properties within the operating temperature range, good reproducibility of the material, and a relationship between resistance values and temperature that follows an interval function (preferably a linear relationship). PT100 thermoresistors are typically used in conjunction with display controllers, paperless recorders, and computers produced by Shaoxing Zhongyi. Directly measure the temperatures of liquid, steam, and gas media, as well as solid surfaces, within the range of -199°C to 600°C in various production processes. Advantages of PT100: The temperature-sensing element of a thermal resistor is made by evenly winding fine metal wires around a frame made of insulating material. When there is a temperature gradient in the medium being measured, the temperature obtained is the average temperature of the medium layer within the range where the temperature-sensing element is located. It is a solid component made up of a temperature-sensitive element (resistive body), leads, insulating material, and a stainless steel sleeve; its outer diameter is generally between φ3 and φ20 mm, with φ8 mm being the most common value. Compared to ordinary thermal resistors, it can reflect the actual temperature of the surface being measured more accurately and quickly, making it suitable for measuring the surface temperatures of liquids and other components. The explosion-proof PT100 thermistor utilizes a specially designed junction box to contain any explosions that might occur due to sparks or arcs within the explosive gas mixture inside its casing; this prevents explosions from occurring at the production site. PT100 thermoresistors can be used for temperature measurement in explosive-hazardous areas within the Bla~B3c classification range. Wiring method for PT100 thermistors: 1. Two-wire system: This is a method in which a wire is connected to each end of the PT100 thermistor in order to transmit the resistance signal. This wiring approach is simple, but since there is always a wiring resistance r associated with the connecting wires, and the value of r depends on the material and length of those wires, this method is only suitable for applications where lower measurement accuracy is sufficient. 2. Three-wire system: The configuration in which one lead is connected to one end of the PT100 thermistor, while two leads are connected to the other end, is known as the three-wire system. This approach is typically used in conjunction with bridges, as it helps to minimize the impact of lead resistance. It is the most commonly used method in industrial process control. The use of a three-wire PT100 thermistor is intended to eliminate measurement errors caused by the resistance of the connecting wires. This is because the circuit for measuring thermal resistors is generally an unbalanced bridge. As one of the bridge arm resistors in a bridge, the connecting wire of the thermoresistor also forms part of the bridge arm resistance; this portion of the resistance is unknown and changes with ambient temperature, resulting in measurement errors. A three-wire system is used, with one wire connected to the power supply terminal of the bridge, and the other two wires connected respectively to the bridge arm where the thermistor is located and to the adjacent bridge arm; this eliminates the measurement errors caused by the resistance of the wiring. 3. Four-wire system: The method in which two wires are connected to each end of the PT100 thermistor constitutes the four-wire system. Two of these wires supply a constant current I to the thermistor, converting R into a voltage signal U; this signal U is then transmitted to the secondary instrument through the other two wires. It can be seen that this type of lead configuration completely eliminates the influence of lead resistance, and is mainly used for high-precision temperature measurement. https://mmbiz.qpic.cn/mmbiz_jpg/MFXXMAGsu1r3ol3ze8licDt5FhvTfEdoZD8csTQaSP40iborhz1SoWlgQkzPPLkXLgiaSWrU23Vc3WTnNEomRN3zg/640?wx_fmt=jpeg Installation requirements for PT100 thermistors When installing PT100 thermistors, it is important to ensure accurate temperature measurement, safety and reliability, as well as ease of maintenance, without affecting the operation of the equipment or production processes. To meet the above requirements, the following points should be considered when selecting the installation location and insertion depth of the thermal resistor: 1. To ensure adequate heat exchange between the measuring end of the thermal resistor and the medium being measured, the location of the measurement point should be chosen carefully; it is advisable to avoid installing the thermal resistor near valves, elbows, as well as in dead corners of pipes and equipment. 2. Thermal resistors with protective sleeves suffer from heat transfer and heat dissipation losses; to reduce measurement errors, they should have a sufficient insertion depth: 1) For thermal resistors used to measure the temperature of the fluid at the center of a pipeline, their sensing end should generally be inserted to the center of the pipeline (whether installed vertically or at an angle). For example, if the pipe diameter of the fluid being measured is 200 millimeters, the insertion depth of the thermoresistor should be around 100 millimeters ； 2) For the temperature measurement of high-temperature, high-pressure, and high-speed fluids (such as main steam temperature), in order to reduce the resistance exerted by the protective sleeve on the fluid and prevent the sleeve from breaking under the influence of the fluid, a shallow insertion method for the protective tube or a heat-shielded thermistor can be employed. For shallowly inserted thermal resistance protection sleeves, the depth of insertion into the main steam pipe should be no less than 75 mm ； The standard insertion depth for a heat-shrink type thermistor is 100 mm. 3) If it is necessary to measure the temperature of the smoke in the flue, even though the flue diameter is 4m, a heat resistor with an insertion depth of 1m will suffice. 4) When the insertion depth of the measuring element exceeds 1 m, it should be installed as vertically as possible, or support frames and protective sleeves should be added. 3. The thermal resistor should be installed as vertically as possible on horizontal or vertical pipes, and a protective sleeve should be used during installation to facilitate maintenance and replacement. 4. When measuring the temperature inside the pipeline, the length of the element should be on the center line of the pipeline (that is, the insertion depth of the protective tube should be half of the pipe diameter). 5. Use high-temperature resistant cables or high-temperature resistant compensation wires in high-temperature areas. Traditional methods to improve the accuracy and stability of industrial resistance temperature measurement focus on component purity, packaging technology, and manufacturing processes ； Thus, a new approach from a computational perspective is proposed, which lays the foundation for improving the systems for temperature value transfer and traceability in precision and industrial platinum resistors; it can be widely applied in the temperature measurement field using industrial PT100 platinum resistors.