Rtd temperature conversion1/28/2024 ![]() ![]() Once the wire is wound onto the bobbin, the assembly is then sealed with a coating of molten glass. The bifilar winding reduces the effective enclosed area of the coil to minimize magnetic pickup and its related noise. The platinum wire is bifilar wound on a glass or ceramic bobbin. Due to the unsupported structure and subsequent susceptibility to vibration, this configuration is still a bit too fragile for industrial environments.Ī more rugged construction technique is shown in Figure 37. Strain-induced resistance changes over time and temperature are thus minimized, and the bird-cage becomes the ultimate laboratory standard. The platinum element remains largely unsupported, which allows it to move freely when expanded or contracted by temperature variations. This is the bird-cageelement proposed by Evans and Burns. The fragility of the structure limits its use today primarily to that of a laboratory standard.Īnother laboratory standard has taken the place of Meyers’ design. This results in a slow thermal response time. This construction minimized strain on the wire while maximizing resistance.Īlthough this construction produces a very stable element, the thermal contact between the platinum and the measured point is quite poor. He wound a helical coil of platinum on a crossed mica web and mounted the assembly inside a glass tube. The classical resistance temperature detector (RTD) construction using platinum was proposed by C.H. As a noble metal, it shows limited susceptibility to contamination. Platinum is especially suited to this purpose, as it can withstand high temperatures while maintaining excellent stability. In fact, the Platinum Resistance Temperature Detector, or PRTD, is used today as an interpolation standard from the oxygen point (-182.96☌) to the antimony point (630.74☌). His choice proved most propitious, as platinum is used to this day as the primary element in all high-accuracy resistance thermometers. Fifty years later, Sir William Siemens proffered the use of platinum as the element in a resistance thermometer. The same year that Seebeck made his discovery about thermoelectricity, Sir Humphrey Davy announced that the resistivity of metals showed a marked temperature dependence.
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