Project Analog - November 2008 - (Page 9)

An Overview of Analog Sensor Conditioning Circuits Contributed by Microchip Technology www.microchip.com / View complete article here IntroductIon Analog sensors produce a change in an electrical property to indicate a change in its environment. This change in electrical property needs to be conditioned by an analog circuit before conversion to digital. Further processing occurs in the digital domain but is not addressed in this article. The applications discussed in this article include electrical, magnetic, temperature, humidity, force, weight, torque, pressure, motion, flow, light and infrared and chemistry. For each type of electrical property, commonly used conditioning circuits are shown. Each circuit has an accompanying list of advantages and disadvantages, and a list of sensor types appropriate for that circuit. The electrical properties covered are voltage, current, resistance, capacitance and charge. In addition, circuit and firmware concerns common to many embedded designs are briefly mentioned, 9 · PROjeCt ANAlOG · VOlUme 2 / NUmbeR 6 Contents Viewpoint Selecting the Proper Amplifier Using a Digital Potentiometer to Optimize a Photo Detection Circuit Resistor Networks in Critical Applications Analog news An excerpt from Application Note AN990 “Analog Sensor Conditioning Circuits—An Overview” including input protection, sensor failure detection, filtering, analog-to-digital conversion and correction of results. BaSIc SIGnal condItIonInG for VoltaGe SenSorS DIFFERENCE AMPLIFIER Figure 1 shows a difference amplifier using an op amp. It presents an impedance of R1 to each end of the sensor (VSEN+ and VSEN-) and amplifies the input difference voltage (VSEN+ - VSEN-). Advantages: • Resistive isolation from the source • Large input voltage range is possible • Rejects common mode noise; it is good for remote sensors • Simplicity Microchip analog page Sample center microchipDIRECT Reference designs/ app notes Technical training http://www.microchip.com http://ww1.microchip.com/downloads/en/AppNotes/00990a.pdf http://www.microchip.com http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog 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

Table of Contents Feed for the Digital Edition of Project Analog - September 2008

Project Analog - September 2008 Contents Viewpoint About Project Analog Sponsor Selecting the Proper Amplifier for Strain Gauge Applications An Overview of Analog Sensor Conditioning Circuits Using a Digital Potentiometer to Optimize a Photo Detection Circuit Resistor Networks in Critical Applications Selecting the Right Op Amp Analog News Contact Microchip New Microchip Products Treelink MINDI™ Active Filter Designer Microchip Advanced Parts Selector (MAPS)

Project Analog - September 2008

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