A resistance temperature device (RTD) is a thermal sensor that works on the measurement principle that the electrical resistivity of any material varies directly with its degree of sensible heat energy. The relationship between the environmental temperatures and the resistance of these devices is highly predictable. This allows for a consistent and accurate measuring of the amount of sensible heat in the detector. When the devices are supplied with stable source of current and resultant voltage drop across the resistor measured, its force that opposes flow of current can be computed, and its sensible heat also determined.
Most commonly used RTD sensing elements constructed of nickel, copper and platinum have a repeatable, and unique and predictable thermal conductivity versus resistance relationship within the thermal operation range. Platinum is the most stable over the largest thermal energy range. Nickel elements have limited range of operation because the amount of change in resistivity per degree of change in internal thermal energy becomes very non-linear above 300 degrees Celsius.
The significant behavior of the metals used in manufacturing resistive elements is the ability to approximate their resistivity versus thermal energy relationship ranging from zero to a hundred degrees Celsius. Industrial standards have also been established so as to ensure the elements meet the required standards and accuracy. Functional characteristics of the sensors can also be found by applying values of nominal resistivity and tolerance.
Apart from the different materials, RTD can be made in two configurations: thin film and wire wound. A wire wound configuration shows an outer wound or an inner coil RTD. Inner coil construction is made up of a resistive coil that runs through an opening in a ceramic, whereas an outer wound consists of winding the resistive material around a glass cylinder or ceramic having a glass dollop.
Thin film elements have a detecting device which is formed by depositing a relatively thin layer of resistive substance, usually platinum, on a ceramic substrate. The main disadvantage of this type is that they are less stable compared to the wire-wound and coiled counterparts. They also have different expansion rates brought about by the substrate deposited that creates a strain gauge effect.
Thin film elements have detecting components that is formed by depositing a relatively thin layer of resistive substance, usually platinum, on a ceramic substance. This layer is always below a hundred angstroms. The thin film deposit is coated with glass or epoxy to protect it from contamination and also to act as strain relief for foreign lead-wires. This type of RTD are however not as stable as the coiled or wire wound types.
Platinum detecting wire should be kept free from any contamination so as to ensure it retains its stability. A platinum film or wire should be supported on a former so that it gets minimal strains from its former or minimal differential expansion, even though it is often resistant to vibration. RTD assemblies manufactured using iron or copper are also used in number of applications.
At very low internal thermal energy of the elements, because there are very few phonons, resistivity of an RTD depends only on boundary scattering and impurities. However, any appliance that use resistance temperature device has excellent accuracy, wide operation range, low drift and is also suitable for precision applications. These outstanding characteristics qualify them to be best in any industrial applications that require high efficiency.
Most commonly used RTD sensing elements constructed of nickel, copper and platinum have a repeatable, and unique and predictable thermal conductivity versus resistance relationship within the thermal operation range. Platinum is the most stable over the largest thermal energy range. Nickel elements have limited range of operation because the amount of change in resistivity per degree of change in internal thermal energy becomes very non-linear above 300 degrees Celsius.
The significant behavior of the metals used in manufacturing resistive elements is the ability to approximate their resistivity versus thermal energy relationship ranging from zero to a hundred degrees Celsius. Industrial standards have also been established so as to ensure the elements meet the required standards and accuracy. Functional characteristics of the sensors can also be found by applying values of nominal resistivity and tolerance.
Apart from the different materials, RTD can be made in two configurations: thin film and wire wound. A wire wound configuration shows an outer wound or an inner coil RTD. Inner coil construction is made up of a resistive coil that runs through an opening in a ceramic, whereas an outer wound consists of winding the resistive material around a glass cylinder or ceramic having a glass dollop.
Thin film elements have a detecting device which is formed by depositing a relatively thin layer of resistive substance, usually platinum, on a ceramic substrate. The main disadvantage of this type is that they are less stable compared to the wire-wound and coiled counterparts. They also have different expansion rates brought about by the substrate deposited that creates a strain gauge effect.
Thin film elements have detecting components that is formed by depositing a relatively thin layer of resistive substance, usually platinum, on a ceramic substance. This layer is always below a hundred angstroms. The thin film deposit is coated with glass or epoxy to protect it from contamination and also to act as strain relief for foreign lead-wires. This type of RTD are however not as stable as the coiled or wire wound types.
Platinum detecting wire should be kept free from any contamination so as to ensure it retains its stability. A platinum film or wire should be supported on a former so that it gets minimal strains from its former or minimal differential expansion, even though it is often resistant to vibration. RTD assemblies manufactured using iron or copper are also used in number of applications.
At very low internal thermal energy of the elements, because there are very few phonons, resistivity of an RTD depends only on boundary scattering and impurities. However, any appliance that use resistance temperature device has excellent accuracy, wide operation range, low drift and is also suitable for precision applications. These outstanding characteristics qualify them to be best in any industrial applications that require high efficiency.
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