Page 486 - Sensors and Control Systems in Manufacturing

CHAPTER 9

Communications

9.1 Introduction
The signals supplied by the sensors enable the processing subsystems
to construct a real-time data of the process at a specific point in time.
In this context, reference is often made to a process control diagram. The
process control diagram is necessary to logically connect individual
signals, to delay them, or to store them. The process of data process-
ing and control can be used in the broadest sense for the processing
of a conventional control system, even a simple one. The task of the
processing and control function device is to connect the data sup-
plied by the sensors as input signals, in accordance with the task
description, and pass data as output signals on to the actuators. The
signals generated are mainly binary signals.

9.2 Single-Board Computer
A single-board computer system is illustrated in Fig. 9.1, with input
and output units suitable for the solution of control problems. The
central processing unit is a microprocessor that coordinates the con-
trol of all sequences within the system in accordance with the pro-
gram stored in the program memory.
A read-only memory (ROM) does not lose its contents even if the
line voltage is removed. In the system in Fig. 9.1, the ROM contains a
program that allows data to be entered via the keyboard and displayed
on the screen. This program is a kind of mini-operating system; it is
called a monitor program or simply a monitor.
A RAM loses its contents when the voltage is removed. It is pro-
vided to receive programs that are newly developed and intended to
solve a specific control task.
The input/output devices enable the user to enter data, particu-
larly programs, through the keyboard into the RAM and to monitor
the inputs.
Binary signals generated by the sensing process can be read in
through the input/output devices, generating an actuating process as

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