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Home > Mall Dynamic > The Working Principle And Resistance Temperature Coefficient OF RTD Thermal Resistance Temperature Sensor
Sensors are devices used by electronic, electrical and mechanical devices to interact with the external environment. These are used to measure various types of physical phenomena, such as voltage, current, acceleration, etc... Sensors use a variety of principles to measure these physical quantities. For example, the piezoelectric effect is used to measure voltage and current, and the Hall effect is used to measure magnetic density... Thermal resistance temperature sensor - A resistance temperature detector is a temperature detection sensor that uses the relationship between temperature and conductor resistance to measure temperature. The sensor is rapidly replacing thermocouples.
The term thermal resistance temperature sensor stands for resistance temperature detector. This sensor is also known as a resistance thermometer. The sensor is used to measure temperature. Typically, they are provided as a length of thin wire made of platinum nickel or copper, wrapped around a ceramic or glass core.
The sensor uses the temperature/resistance relationship of the wire to measure temperature.
By using the relationship between temperature and resistance, it is possible to find the amount of change that occurs in the resistance value of the sensor, that is, the degree of temperature change. Platinum has a stable resistance-temperature relationship over a wide temperature range.
For nickel, the resistance change due to temperature change becomes nonlinear at temperatures above 300 ° C. Depending on their behavior, in different temperature ranges, the material is selected to make the thin wire, which is used for the thermal resistance.
Thermal resistance temperature sensors can be built in different forms, and in some cases they are superior to thermocouples in terms of stability, accuracy, and repeatability. Thermal resistance temperature sensors require a power supply to operate.
Unlike thermocouples, which use the Seebeck effect to generate voltage, thermal resistance temperature sensors use resistance.
The Working Principle OF Thermal Resistance Temperature Sensor:
Thermal resistance temperature sensors work based on the resistance-temperature relationship of the material in which they are constructed. Measure the amount of change in the resistance value of the material due to each degree increase in temperature and calibrate the sensor accordingly.
Resistance components are fragile, and they always need insulation. The insulator leads are connected to the element. For insulators with temperatures below 250 o C, such as silicone rubber, PVC is used. A metal alloy that is chemically inert to temperature is used as a protective sleeve to house the measuring points and leads.
The temperature range from 0 0 C to a linear change in temperature value is considered to be the temperature range of the sensor. This depends on the wire material used in the sensor. Platinum is used in a temperature range of up to 660 ° C. Nickel is suitable for temperatures below 300 ° C.
The linear approximation of the resistance-temperature relationship between metals at 00 C and 100 0 C is considered to be a distinguishing feature of metals used as wires in sensors.
The resistance temperature coefficient is
The working principle and resistance temperature coefficient of RTD thermal resistance temperature sensor
Where R 0 and R 100 are the resistance of the sensor at 0 ° C and 100 ° C, respectively.
The resistance temperature sensor features a coil made of thin wire that is wound around a glass or ceramic core and is made of platinum by RTD element winding pieces, as this metal resists harsh environments, corrosion and oxidation. Sometimes copper or nickel is also used.
These RTDS re sometimes more than just wires. But, by far, platinum is the # good choice, with many advantages. Here are some of the benefits that platinum RTDS offer:
Platinum is chemically inert
It provides a stable and almost linear temperature-resistance equation
Platinum as a metal provides a good enough temperature coefficient to enable RTDS to sense rapid resistance changes
In general, 2 - and 3-wire RTDS are widely used, which largely depends on the cable. RTDS typically have two, three, or four wires. 2-wire RTDS are typically used in non-critical applications where only an approximation of the temperature change is required if the temperature change will not occur.
On the other hand, 3-wire RTDS have been widely used in industry. The accuracy of the RTD depends to some extent on the number of wires. If the number of wires is higher, the accuracy is better. A variety of RTD configurations are available depending on temperature or resistance values,
which can be customized to suit specific industrial applications.
Any RTD contains five main components as part of its structure. Details are as follows:
Resistive element: This is the temperature sensing element, and in most cases, it is platinum.
Line: As mentioned earlier, there are 2, 3 or 4 line RTDS. The wires are insulated and can be protected with Teflon fiberglass.
Pipe material: Usually used for industrial assembly, pipes are made of Inconel or 316 stainless steel.
Connecting accessories: These include standard accessories for thermocouples, such as welding or compression accessories.
The outer diameter of the RTD: approximately 6tmm, located just above the resistance element.
Cold end termination: RTDS can terminate cold end connections using a plug or bare wire.
When a small amount of current passes through the element, a voltage proportional to the resistance is measured and converted into a temperature calibration unit. The temperature is proportional to the resistance of the RTD. This means that when the temperature rises, so does the resistance of the RTD.
This change in temperature is sensed by the detector and sends a message to the system accordingly. This is how RTDS work - the current is hindered by the increase in temperature sensed by the resistance element. The resistance is measured in ohms. Depending on the application requirements and RTD type,
the response time may be as high as 0.5 seconds.
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