This document provides an overview of sensors and primary transducers used in process and automatic control systems. It discusses various types of sensors for measuring temperature, pressure, speed, and other process variables. The key types covered include thermocouples, resistance temperature sensors, pressure sensors using Bourdon tubes, diaphragms, and other mechanisms, as well as optical and magnetic sensors for measuring speed of rotation. The document aims to familiarize the reader with common input sensors and their basic working principles.