thermocouples2 - Practical Temperature Measurements...

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Practical Temperature Measurements Thermocouple TEMPERATURE T 0 Self-powered 0 Simple q Rugged 0 lnexpensrve q Wide variety 0 Wide temperature range 0 Non-linear 0 Low voltage 0 Reference required 0 Least stable 0 Least sensitive RTD TEMPERATURE T 0 Most stable 0 Most accurate 0 More linear than thermocouple 0 Expensive 0 Current source re- quired 0 Small AR 0 Low absolute reststance 0 Self-heating Thermistor 0 High output U Fast 0 Two-wire ohms measurement U Non-linear U Lrmrted temperature range 0 Fragile 0 Current source re- qutred 0 Self-heatmg I.C. Sensor c $2 IA zc : -T TEMPERATURE 0 Most linear 0 Highest output 0 lnexpensrve i3 T <200°C 0 Power supply re- quired 0 Slow 0 Self-heating 0 Limited configurations Figure 1 TABLE OF CONTENTS APPLICATION NOTES-PRACTICAL TEMPERATURE MEASUREMENTS Page Common Temperature Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z-7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8 Z-9 The Thermocouple. ................................................ ReferenceJunction z-9 ................................................. Reference Circuit Z-10 .................................................. Hardware Compensation Z-11 ............................................ Voltage-to-Temperature Conversion. Z-12 ................................... Z-13 Practical Thermocouple Measurements ............................ z-15 Noise Rejection. ................................................... PoorJunctionConnection Z-15 ................................ . . .. z-17 Decalibration. .......................................... ::. .::. .:: : Z-17 Shuntlmpedance . GalvanicAction Z-17 .................................................... Thermal Shunting Z-18 Wire Calibration Z-18 Diagnostics Z-18 ....................................................... Summary Z-19 ........................................................ Z-20 The RTD ........................................................... History z-21 Metal Film RTD’s Z-21 Resistance Measurement. Z-21 ........................................... SWire Bridge Measurement Errors Z-22 .................................... Resistance to Temperature Conversion Z-23 PracticalPrecautions ................................. Z-23 ............................................... Z-24 z-7
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Software Viruses Software viruses are a very real threat, attacking computer systems throughout the world. They can cause a loss or destruction of data, and they are notoriously difficult to track down, much less defeat. Computer virus programs are written solely for the self- gratification of the author. Virus authors are looking for notoriety, through malicious acts of destroying data, whether in a simple floppy disk PC or a large mainframe computer. Many users have lost valuable data and programs to viruses. There have been many confirmed reports of virus attacks on both IBM PC and Apple Macintosh systems. You can protect yourself from viruses, with a little work and some common sense. First, however, it’s necessary to understand how viruses work. What is a Virus? Virus programs can take many forms, but some of the most common types involve an author’s altering a popular program, usually a public-domain or ‘shareware‘ program that’s available on many public bulletin board systems. After the author alters the program to include the virus code, the program runs as expected, but the virus is also triggered. Most viruses will attack the system files of the hard disk, either destroying or corrupting them. Even if it does nothing else, a virus will slow you down. Each time the virus is triggered, it can grow, taking up valuable disk space and causing the infected files to load more slowly. But most viruses are more malicious: After your system has been infected, you may find your hard disk reformatted, data files corrupted, or you may have constant small problems, such as a strange, unusual screen display.
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thermocouples2 - Practical Temperature Measurements...

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