Developing A Precise Pt100 RTD Simulator For SPICE
by Thomas Kuehl, Senior Applications Engineer, Texas Instruments Incorporated

It is fairly common practice for engineers to pre-design and test their analog circuits using a circuit simulation program before an actual prototype is assembled. Although a variety of SPICE-based circuit simulators are available for purchase, several semiconductor companies are now providing their customers with a free, abbreviated version of the full-featured program. When compared, these simulation programs may provide fewer analysis options, fewer convenience features and sometimes node and device limitations. However, TINA-TI (TI's offering to designers) is powerful enough to handle almost any circuit simulation involving signal conditioning elements and sensors.

The resistance temperature detector (RTD) is a popular sensor commonly employed in temperature measurements. Its resistance changes in a near linear fashion, increasing with temperature. Although some RTDs are available for the full -200ºC to +850ºC operational range, more often they are specified for a narrower range such as -75ºC to +250ºC, or -200ºC to +650ºC. The particular range is dependent on the application. RTDs are resistive elements comprised of different metal and metal alloys such as platinum, copper, nickel, nickel-iron and molybdenum. Each type is intended for a particular temperature range, resistance and accuracy requirements. The element resistance range extends from about 25 Ω to 1 kΩ, for commonly-available RTDs.

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