Richards Thermocouple and Temperature Sensor Catalog 16

Resistance Temperature Detectors (RTDs) - Platinum - Selection Guide

Resistance Temperature Detector (RTD) Selection Guide

√ Step #1 - Select the Ohms of the Element: When choosing a RTD (Resistance Temperature Detector or Platinum Resistance Thermometer) for your application, you will first need to determine the ohms of resistance for the platinum element. This is determined by the capability of your temperature indicating instrument. The Richards RTD sensor is available in 100 ohm, 500 ohm, and 1000 ohm configurations. The ohm value is the base resistance of the platium element at a reference point of 0°C. In typical industrial applications the 100 ohm type is the most commonly used element and is the standard in this catalog. √ Step #2 - Select the Alpha: RTDs have a temperature coefficient or “curve” of either .003920 ohms/ohms/°C or .003850 ohms/ohms/°C. This value is commonly called the alpha of the sensor. The .00392 or “ American ” alpha is the U.S. industral standard and the Japanese Standard (JIS C1604-1989). The .00385 or “ European ” alpha is the German (DIN 43760-1980), British (BS 1904-1984), and the International Electrotechnical Commission (IEC 751-1983) standard. In typical industrial applications the “European” curve is more commonly used than the “American” curve and is also the standard alpha in this catalog. √ Step #3 - Select the Accuracy: The accuracy of RTD elements are freqauently classified using the DIN 43760 classification standard. This classification is also used by the International Electrotechnical Commission (IEC 751). The classes are divided into four groups (A, B, C, D) by the amount of allowable resistance and temperature deviation over a temperature range. These base values are usually listed at 0°C. The smaller the deviation the lower the class (A) and the greater the accuracy of the sensor. In order to give our customers a high quality product, all standard Richards RTD sensors perform with an accuracy greater than class A. The standard Richards RTD has an accuracy of ±0.04% resistance or ±0.1°C , which is more accurate than the DIN Class A. We also offer a very high accuracy version, which can be specified by the “ AA ” (American Curve) or “ EE ” (European Curve) in our part number. For comparision purposes, the Richards and DIN accuracy classes (at 0°C) are shown below. Richards Premium AA or EE = ±0.02% resistance or ±0.05°C DIN Class A = ±0.06% resistance or ±0.15°C Richards Standard A or E = ±0.04% resistance or ±0.1°C DIN Class B = ±0.12% resistance or ±0.3 °C √ Step #4 - Select the Figure which best represents the Style RTD you require: Browse through the catalog and locate one of the RTD photographs which would best suit your application. Due to space limitations, if you do not find exactly what you are looking for, phone one of our sales engineers, and we can help with the part number. √ Step #5 - Fine Tune the Part Number: After locating a figure and part number, you can fine tune the sensor for your application. If you require an American curve sensor and not the European curve, change the “ E ” to an “ A ” in the part number. If you require a 500 Ω and not the standard 100 Ώ sensor, change the “ 11 ” in the part number to “ 51 ”. 1000 Ώ sensors can be ordered by changing the “ 11 ” to “ 101 ”. Substitute any “ X ” and “ Y ” characters with your length requirements. RTDs are provided in four wire configurations as standard. This is the most accurate configuration. Note: if you are using a transmitter you may be only able to use a three wire sensor. This can be designated by changing the “ 4 ” in the part number to “ 3 ”. Two wire RTDs can be specified by changing the “ 4 ” to “ 2 ” in the part number. Note the RTD wiring congiguration diagrams shown on the next page. The standard metal sheath for RTD elements is 1/4” diameter made of 316 stainless steel. Inconel 600 sheaths can be specified by changing the “ 16 ” in the part number to a “ 09 ”. Example part number: 4E164-11-12-24 is a four wire, European curve, 316 Stainless Steel 1/4 inch diameter sheath, 100 Ώ, 12” probe, 24” probe and leads overall. Note: Richards standard RTDs have a maximum service temperature rating of 400°C ( 752°F ). Our high temperature RTDs have a maimum service temperature rating of 650°C ( 1202°F ). If you would like to specify this option, add a “ H ” after the curve designation letter ( A or E ) in the catalog number. Example Part Number: 4EH164-11-12-24 High Temperature , Four wire, European curve, 316 Stainless Steel 1/4 inch diameter sheath, 100 Ώ, 12” probe, 24” probe and leads overall.

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