Pt100 thermal resistance: briefly explain the principle of thermal resistance and the method of connecting wires

pt100 thermal resistance:Thermal resistance is a common temperature detector in the middle and low temperature area. Its main characteristics are high measurement accuracy and stable performance. Among them, the resistance of platinum heat has high measurement accuracy. It is not only widely used in industrial temperature measurement, but also made as a standard reference device.
Thermal resistance temperature measurement principle
Almost all thermal resistors are made of pure metal materials, and platinum and copper are now used more frequently.
The company uses a large number of PT100 platinum resistance temperature measuring body. The three-wire system is used to eliminate measurement errors caused by the resistance of the connecting wires. This is because the circuit that measures the thermal resistance is generally an unbalanced bridge. As one of the bridge resistors of the temperature measuring resistor bridge, its connecting lead (from the temperature measuring resistor body to the central control room) also becomes a part of the bridge resistor. This part of the resistor is unknown and changes with the ambient temperature, resulting in measurement errors. A three-wire system is adopted. One wire is connected to the power end of the bridge, and the remaining two are respectively connected to the arm with the thermal resistor and its adjacent arm, this eliminates measurement errors caused by wire line resistance.
At present, there are three main methods for wire connection of thermal resistance.
Two-wire type: the two ends of the thermal resistance are connected to a wire to lead out the resistance signal is called two-wire type. The method of connecting the wire is very simple, but there must be a resistance r of the wire when connecting the wire. The size of r is related to the material and length of the wire.
Three-wire type: one end of the root of the thermal resistance is connected to the wire, and the other end is connected to two wires. This method is usually used in combination with a bridge, which can well eliminate the influence of wire resistance, and is often used for industrial process control.
Four-wire system: The method of connecting two wires at both ends of the root of the thermal resistance is called four-wire system, in which the two wires provide constant current I to the thermal resistance, convert R into voltage signal U, and then import U into the secondary meter through the two wires. Therefore, the wire method can completely eliminate the influence of wire resistance and is mainly used for high-precision temperature detection.
The thermal resistance adopts a three-wire connection method. This is because the circuit for measuring the thermal resistance is generally an unbalanced bridge. As one of the bridge resistors of the temperature measuring resistance bridge, its connecting lead (from the temperature measuring resistor to the central control room) also becomes a part of the bridge resistor. This part of the resistor is unknown and changes with the ambient temperature, resulting in measurement errors. The three-wire system is adopted to connect a wire to the power supply end of the bridge, the remaining two are connected to the arm with the thermal resistor and the arm adjacent to it, respectively, thereby eliminating the measurement error caused by the resistance of the wire line.
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