Introduction Resistance elements come in many types conforming to different standards, capable of different temperature ranges, with various sizes and accuracies available. But they all function in the same manner: each has a pre-specified resistance value at a known temperature which changes in a predictable fashion. In this way, by measuring the resistance of the…
read moreGENERAL CONSIDERATIONS Vinyl offers low Cost, good flexibility, fair electricals, a good general purpose material. Irradiated PVC offers moderate cost, heat resistance, good electrical and physical properties, excellent abrasion, cut-through and solder resistance. Teflon offers high cost, high temperature rating, excellent chemical resistance, excellent electrical properties, poor cut through resistance. Tefzel offers high cost, good…
read moreThermometrics manufactures a full line of standard and custom weld pad RTD’s. The weld pad (tube skin) termination allows a temperature sensor to be welded directly onto piping or other metal surfaces to sense the surface temperature. Weld pads are most commonly used in fired heater tubes, refinery heater tubes, boilers and furnaces in refineries,…
read moreImagine that you are an Instrumentation Engineer. You are looking at the prints for a new plant, and you see the many locations marked out for temperature transducers. You ask yourself; What has been specified to fill each space? RTD for their high accuracy and linearity? Or thermocouples because of their lower cost and familiarity?…
read moreTheory of Operation A basic physical property of a metal is that its electrical resisivity changes with temperature. All RTDs are based on this principle. The heart of the RTD is the resistance element. Several varieties of semi-supported wire-wound fully supported bifilar wound glass, and thin film type elements are shown here. Some metals have…
read moreBayonet RTD Bayonet RTDs, Thermistors and Thermocouple temperature sensors are commonly used in extruder and plastic processing industries. These sensors provide accurate temperature control for the best plasticizing combination of plastic material, mold and design. Bayonet RTD temperature sensors are available in 6 configurations; Adjustable Immersion Bayonet on Flex Armor Bayonet on Flex Armor with…
read moreRTD Sensor Accuracy and Tolerance Standards The industry standard for platinum RTD’s according to IEC-751 is + /- 0.12% (of resistance) at 0°C, commonly referred to as Class B accuracy. This will provide an accuracy of + /- 0.3°C at 0°C, which is quite good if you compare it to the + /- 2.2°C…
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Selecting The Right Sensor: Imagine that you are an Instrumentation Engineer. You are looking at the prints for a new plant, and you see the many locations marked out for temperature transducers. You ask yourself; What has been specified to fill each space? RTD for their high accuracy and linearity? Or thermocouples because of their…
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