tailieunhanh - Ebook Electrical engineering (2nd edition): Part 2

The author presents a concise overview of topics that is enhanced by real world applications. This book is a survey of the foundations of electrical engineering, and emphasizes principles of circuits, electronics, systems and electromechanics for electrical engineers. | CHAPTER 4 The Real World The real world is the place where you and I live. It isn’t in this book or in a simulation or even the scribbles on a schematic. All those things are representations of the real world. They help us understand how the real world works. At some point, all the circuits we create and design will interface with the real world, even if it is just a button to press or display to look at. It follows that we should talk a bit about some of the things we use to hook our circuits up to the big, bad world. BRIDGING THE GAP If this book had been written back when computers were analog, this section wouldn’t even be needed. As it is, the proliferation of those pesky little digital chips gives it top billing. You need to bridge the gap between the analog and the digital at some point if you want to market your latest gadget as “way cool digital technology.” Knowing a bit about how to make the analog-to-digital leap seems like a good idea. Analog vs. Digital If we put analog in one corner of a boxing ring and we put digital in the other corner and then we let them duke it out, who do you think would win? In today’s world, digital is all the rage, but what really sets it apart from analog? Let’s find out. 141 142 CHAPTER 4 The Real World What is analog? Is it merely some ancient term lost in the world of today’s digital engineers? No; analog basically means a continuously variable signal. It means that the item being measured can be chopped up into infinite little pieces over time. Say, for example, a signal changes from A to B over a 1-second interval. If you look at it before 1 second is over it will be somewhere between A and B. It is a continuous variable. No matter how small you slice up the time segments, there is still a signal with information there. The world as we perceive it is analog in nature. Colors blend infinitely from one end of the spectrum into the other. The sound as a car races by on the street is heard in a continuously .