TABLE OF CONTENTS This chapter will help you understand active devices, how they are used in instrument applications, and the difference between analog and digital circuits.
In this chapter the following points are discussed.
The terms active and passive as applied to electronic components
Signal amplification, gain adjustment, and feedback in amplifiers
Operation of amplifiers
Different types of amplifiers
The difference between digital and analog circuits
The instrument amplifier
Introduction to digital circuits
Conversion of analog signals to digital signals
The output from measuring or sensing devices is usually converted into electrical signals, so that they can be transmitted to a remote controller for processing and eventual actuator control or direct actuator control. Consequently, as well as understanding the operation of measuring and sensing devices, it is necessary to understand electricity and electronics as applied to signal amplification, control circuits, and the transmission of electrical signals. Measurable quantities are analog in nature, thus sensor signals are usually analog signals but can sometimes be converted directly into digital signals. Transmission of information over long distances can use analog or digital signals. Because of the higher integrity of digital signals compared to analog signals, and the fact that processors use digital signals, this form of transmission is preferred. Since both forms of transmission are in common use, an understanding of both signal forms is needed and will be discussed.
Passive components resistors, capacitors, and inductors were studied in Chaps. 2 and 3. This chapter deals with active components, i.e., devices such as bipolar...
