Real World Instrumentation with Python

Chapter 2. Essential Electronics

Electricity is actually made up of extremely tiny particles called electrons that you cannot see with the naked eye unless you have been drinking.

—Dave Barry, American humorist

Although this is a book primarily about instrumentation software, we must also consider what the software is interacting with in the physical world—in other words, the hardware aspects of instrumentation. This chapter is intended to provide a general high-level overview of electricity and basic electronics from an instrumentation perspective, without delving too deeply into the theory and physics behind it all.

Electronics is a deep and vast field of study. Out of a desire to avoid turning this book into a reference work on the subject, some topics are lightly glossed over here, or not even covered at all. If you’re already familiar with electronics at more than just an Ohm’s law level, feel free to skip over this chapter and forge ahead, but if you’re not quite certain what Ohm’s law is, or about the difference between a current source and a current sink, what the term “waveform” means, or how digital and analog input and output differ from one another, this chapter is for you.

We’ll start off with a general description of electric charge and current, and then present some of the symbols used in schematic diagrams. Next, we’ll take a look at very basic DC and AC circuits, followed by a discussion of the types of input and output found in instrumentation systems from an electrical ...