Applied Process Control

4Basic Elements Used in Plant Control Schemes

So far the focus has been on open-loop systems, that is how a system naturally behaves before any intelligence is added to it. Now simple signal manipulations and rerouting, including feedback, will be considered. The ‘base layer’ control scheme for a processing plant is generally constructed using signal interconnections between a number of standard elements. Configuration software for SCADA and distributed control systems allow one to do this graphically. This chapter focuses on the standard functions made available in these schemes.

4.1 Signal Filtering/Conditioning

Measurement signals can be altered at three points:

1. Some measurement devices (such as DP cells) have on-board electronic or digital ...