This book talks about sensors: inductive, capacitive, magnetic, optical, vision systems, encoders, and others. Sensors to detect strength, position, level, shape, or color. The operating principles and construction characteristics are explained. Practical examples are given, and typical applications are shown with a guide to choose. It is suggested how to draw sensors in electrical patterns and how to electrically connect them. What's in this book that I couldn't find on the Internet? Nothing. But there isn't a website on the Internet that treats all these devices in a single document that's easy and quick to consult and full of images.