Project Analog - January 2008 - (Page 10) Selecting the proper temperature Sensing technology for your application Content contributed by Microchip Technology / Chandler, AZ / www.microchip.com introduction Of all of the sensing technologies, temperature sensing is the most common. The most popular temperature sensors used today are the thermocouple, Resistive Temperature Device (RTD), thermistor and silicon-based temperature sensors. Each of these sensor technologies caters to specific temperature ranges and environmental conditions. The sensor’s temperature range, ruggedness and sensitivity are just a few characteristics that are used to determine whether the device will satisfy the requirements of the application. This article explains the most popular temperature-sensor technologies and provides insight into how to determine which sensor 10 · projeCt analog · jan 08 Contents Viewpoint Wireless sensor networks Temperature sensing technology Analog news is most appropriate for the given application. therMocouPleS A thermocouple is composed of two different metals soldered together on one end. A temperature difference between the two ends of the thermocouple will cause a voltage differential. This voltage will change as a function of temperature. Any junction of two dissimilar metals will form a thermocouple (or thermojunction), but some metal combinations work better than others. There are a variety of different thermocouple types available, each with its own set of advantages and disadvantages. Regardless of the type, thermocouples have a wide operating-temperature range, fast response time and are very robust, making them well suited for extreme conditions such as cryogenics and other industrial applications. However, thermocouples also possess some disadvantages. First, the voltage change that is induced across a thermocouple is very small. Most thermocouples output only 50 mV to 80 mV across their entire operating-temperature range, which could span 800 degrees or more! Additionally, thermocouples are highly nonlinear and require significant linearization algorithms. It is important to note that a thermocouple will provide a relative temperature; hence, the temperature at Microchip analog page Thermal management overview Sample center microchipDIRECT Reference designs/ app notes Technical training http://www.microchip.com http://www.microchip.com http://www.microchip.com/analog http://www.microchip.com/analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2543¶m=en021419&pageId=79 http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2543¶m=en021419&pageId=79 http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423
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