Page 305 - Sensors and Control Systems in Manufacturing

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The RS-232 interface is the most widely used interface in data
acquisition for sensors and control systems. However, it is not always
suitable for distances longer than 50 m or for multidrop network
interfaces. The RS-422 protocol has been designed for long distances
(up to 1200 m) and high-speed (usually up to 56,000 bits/s) serial
data communication. The RS-485 interface can support multidrop
data communication networks.
5.7.7 Software
The driving force behind any data acquisition for sensors and control
systems is its software control. Programming the data acquisition for
sensors and control systems can be accomplished using one of three
methods:

• Hardware-level programming is used to directly program the
data acquisition hardware’s data registers. In order to achieve
this, the control code values must determine what will be writ-
ten to the hardware’s registers. This requires that the program-
mer use a language that can write or read data from the data
acquisition hardware connected to the PC. Hardware-level
programming is complex, and requires significant time—time
that might be prohibitive to spend. This is the reason most
manufacturers of data acquisition hardware supply their cus-
tomers with either driver-level or package-level programs.
• Driver-level programming uses function calls with popular pro-
gramming languages such as C, PASCAL, and BASIC, thereby
simplifying data register programming.
• Package-level programming is the most convenient technique of
programming the entire data acquisition system. It integrates
data analysis, presentation, and instrument control capabili-
ties into a single software package. These programs offer a
multitude of features, such as pull-down menus and icons,
data logging and analysis, and real-time graphic displays.

5.8 Developing CIM Strategy with Emphasis on
Sensors’ Role in Manufacturing
To develop a comprehensive CIM strategy incorporating sensors and
control systems, an enterprise must begin with a solid foundation,
such as a CIM architecture. A CIM architecture is an information sys-
tem structure that enables the industrial enterprise to integrate infor-
mation and business processes. It accomplishes this by (1) establish-
ing the direction integration will take and (2) defining the interfaces
between the users and the providers of this integration function.
Figure 5.14 shows how CIM architecture answers the enterprise’s
integration means. A CIM architecture provides a core of common