Sensors & Instruments Solutions Guide - MINCO - #15

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INTRODUCTION | Page 1-15 TCR differentiates RTDs by their resistance/temperature curves. Sometimes called alpha ( á ), it is specified in various ways by different manufacturers. In this guide TCR is the RTD’s resistance change from 0 to 100°C, divided by the resistance at 0°C, divided by 100°C: For example, a platinum thermometer measuring 100 Ù at 0°C and 139.11 Ù at 100°C has TCR 0.00391 Ù/Ù/°C: For a copper RTD, 10 Ù at 25°C, TCR is: Stated another way, TCR is the average resistance increase per degree of a hypothetical RTD measuring 1 Ù at 0°C. The most common use of TCR is to distinguish between curves for platinum, which is available with TCRs ranging from 0.00375 to 0.003927. The highest TCR indicates the highest purity platinum, and is mandated by ITS-90 for standard platinum thermometers. There are no technical advantages of one TCR versus another in practical industrial applications. 0.00385 platinum is the most popular worldwide standard and is available in both wire-wound and thin-film elements. In most cases, all you need to know about TCR is that it must be properly matched when replacing RTDs or connecting them to instruments. RTD and thermocouple tables are available online at www.minco.com/sensorcalc/ You can create and store tables in a variety of formats. You can also enter resistances and coefficients for custom tables, using Callendar-Van Dusen or ITS-90 equations. SensorCalc Program Thread specifications Wire gauge conversion Ingress Protection (IP) Codes Approximate US Enclosure Type Equivalent to IPXX Type IP Type IP Type IP 1 10 3S 54 6 & 6P 67 2 11 4 & 4X 55 12 & 12K 52 3 54 5 52 13 54 3R 14 First Number Protection against solid bodies Second Number Protection against liquid 0 No protection No protection 1 Objects > 50 mm Vertically dripping water 2 Objects > 12 mm 75° to 90° dripping water 3 Objects > 2.5 mm Sprayed water 4 Objects > 1 mm Splashed water 5 Dust-protected Water jets 6 Dust-tight Heavy seas 7 Effects of immersion 8 Indefinite immersion Wire Gauge Number AWG Cross Sectional Area mm2 Resistance Stranded Solid Ù/ft. at 25°C 30 0.057 0.051 0.1058 28 0.089 0.080 0.0666 26 0.141 0.128 0.0418 24 0.227 0.205 0.0262 22 0.355 0.324 0.0165 20 0.563 0.519 0.0103 18 0.897 0.823 0.0065 Thread Applicable specifications G1/2 • ISO 228/1 • DIN 259 • BS 2779 • JIS B0202 R1/4 R1/8 • ISO 7/1 • DIN 2999 • BS 21 • JIS B0203 Miscellaneous Specifications and Codes Temperature Coefficient of Resistance (TCR) See whitepaper Resistance Thermometry : www.minco.com/download-media.aspx?id=2284