The previous chapter introduced two critically important components found in any electronic control system: sensors and actuators. This chapter explains the operation of the sensors and actuators used throughout a modern car. Special emphasis is placed on sensors and actuators used for power train (i.e., engine and transmission) applications since these systems normally employ the largest number of such devices. However, this chapter will also discuss sensors found in other subsystems on modern cars.

In any control system, sensors provide measurements of important plant variables in a format suitable for the digital microcontroller. Similarly, actuators are electrically operated devices that regulate inputs to the plant that directly control its output. For example, as we shall see, fuel injectors are electrically driven actuators that regulate the flow of fuel into an engine for engine control applications.

Recall from Chapter 2 that fundamentally an electronic control system uses measurements of the plant variable being regulated for feedback control. The measured variable is compared with a desired value for the variable to produce an error signal. The electronic controller generates output electrical signals that regulate inputs to the plant in such a way as to reduce the error to zero.

As will be shown throughout the remainder of this book, automotive electronics have many examples of electronic control in virtually every subsystem. Modern automotive electronic control systems use microcontrollers based on microprocessors (as explained in Chapter 4) to implement almost all control functions. Each of these subsystems requires one or more sensors and...