6158C_Unit2 - UNIT 2 Digital Signals: The basics of digital...

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Page 1 Version 1.09 UNIT 2 Digital Signals: The basics of digital encoding and the use of binary systems. Your Name Date of Submission CHEMISTRY 6158C Department of Chemistry University of Florida Gainesville, FL 32611 (Note: Much of the material in this handout was rewritten/updated in 2001 by graduate student Andrew K. Ottens.)
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Page 2 Version 1.09 Introduction In the previous unit we examined analog signals and the use of transducers to encode electrical information. This unit will cover digital signals, most often used by computers and other integrated circuits to encode information. Since most instruments today manipulate information via digital processes, it is important to learn what it means to be digital, and the basics regarding digital logic. What is digital? Say the word digit, and you think of numbers and counting. In the digital world we deal with discrete integers, whole number values. To sum up digital, think of signals as specific values; on/off, true/false, 1/0. A light switch is digital in nature. The switch is up, and the light is on. When the switch is down, the light is off. There isn’t a middle value with a conventional light switch. It’s the same way with digital encoding. This is completely different from analog, which could be looked at as a dimmer switch. The light level is not encoded as on or off, but as many variable values between the two extremes of on and off. You might think that you can get more detail with an analog signal, since there are many possible values. In some sense this is correct. Theoretically, the dimmer switch can supply many more values than the on/off switch, but there is good reason why computers are digital in nature. The transistor, first produced by Bell Labs in 1949, is the light switch of the electronics world. Transistors are solid state components that can turn on or off depending on input signals received. Each transistor acts as an on/off, or 1/0 switch, and if you put a lot of them together, you get many more possibilities. All of a sudden you have similar detail from a digital device as you do from an analog equivalent, only smaller, more consistent and much more versatile. One of the most obvious uses of transistor technology is in your computer. Today it’s not uncommon to find tens of millions of transistors on a single silicon wafer 0.5 inches square. But the beauty of a microprocessor is its ability to be programmed. You can get a computer to do just about anything, because software can be used to reconfigure the transistors in many ways. Most analog technology is hardwired – it cannot learn new tricks. Basics In the last unit we discussed electrical quantities: voltage, current, charge, and power. Digital signals are often electrical in nature.
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This note was uploaded on 12/11/2011 for the course CHM 6158c taught by Professor Polfer during the Spring '11 term at University of Florida.

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6158C_Unit2 - UNIT 2 Digital Signals: The basics of digital...

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