There are three main ways to lead the national standard thermal resistor

Two-wire system: The method of connecting a wire at each end of the thermal resistor to lead out the resistance signal is called the two-wire system: This lead method is very simple, but since the connecting wire must have a lead resistance r, the size of r is related to the material and length of the wire, so this lead method is only suitable for occasions with low measurement accuracy
Three-wire system: The method of connecting a lead at one end of the root of the thermal resistor and two leads at the other end is called the three-wire system. This method is usually used in conjunction with a bridge, which can better eliminate the influence of lead resistance and is the most commonly used lead resistance in industrial process control.
Four-wire system: The method of connecting two wires at each end of the root of the thermal resistor is called the four-wire system, in which two leads provide a constant current I for the thermal resistor, convert R into a voltage signal U, and then lead U to the secondary instrument through the other two leads. It can be seen that this lead method can completely eliminate the influence of lead resistance, and is mainly used for high-precision temperature detection.
The thermal resistor adopts a three-wire connection method. The three-wire system is used to eliminate the measurement error caused by the resistance of the connecting wire. This is because the circuit for measuring the thermal resistor is generally an unbalanced bridge. The thermal resistor is a bridge arm resistor of the bridge, and its connecting wire (from the thermal resistor to the central control room) also becomes a part of the bridge arm resistor. This part of the resistance is unknown and changes with the ambient temperature, causing measurement errors. Using a three-wire system, one wire is connected to the power supply end of the bridge, and the other two are connected to the bridge arm where the thermal resistor is located and the bridge arm adjacent to it, thus eliminating the measurement error caused by the wire line resistance. The three-wire connection method is generally used in industry.
What is the principle of pt100 thermal resistor?
Thermal resistors are widely used in industry, and there are many types to meet the diversified needs of users. Among them, pt100 thermal resistor is the most commonly used temperature sensor in industry. It works on the principle that the resistance value of metal platinum wire changes with temperature.
Principle of pt100 thermal resistor
pt100 thermal resistor, its resistance value is proportional to the change of temperature. The relationship between the resistance value and temperature of pt100 is: when the temperature of pt100 is 0℃, its resistance value is 100 ohms, and when it is 100℃, its resistance value is about 138.5 ohms.
Its industrial principle
When pt100 is at 0 degrees Celsius, its resistance value is 100 ohms, and the resistance value of pt100 thermocouple will increase at a uniform rate as the temperature rises. The resistance value and temperature of metal thermal resistors can generally be expressed by the following approximate relationship, that is, rt=rt0[1+α(t-t0)], where rt is the resistance value at temperature t; rt0 is the corresponding resistance value at temperature t0 (usually t0=0℃); α is the temperature coefficient. The relationship between the resistance value and temperature of semiconductor thermistors is rt=aeb/t, where rt is the resistance value at temperature t; a and b are constants depending on the structure of the semiconductor material. The above is about the principle of pt100 thermal resistor. I hope you can master this principle before using it, which can effectively help you use thermal resistor better.
Pt100 is a platinum thermal resistor, and its resistance is proportional to the change in temperature. The relationship between the resistance and temperature change of PT100 is: when the temperature of PT100 is 0℃, its resistance is 100 ohms, and at 100℃, its resistance is about 138.5 ohms. Its industrial principle: when PT100 is at 0 degrees Celsius, its resistance is 100 ohms, and its resistance will increase at a uniform rate as the temperature rises.
Thermal resistor is a primary element that converts temperature changes into resistance changes. It is usually necessary to transmit the resistance signal to the computer control device or other primary instrument through the lead wire. Industrial thermal resistors are installed at the production site, and there is a certain distance between them and the control room, so the lead wire of the thermal resistor will have a greater impact on the measurement results.