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PID Algorithm Tuning
Using the Status System
Chapter 3
Tuning control loops is an extensive subject in itself. A proper discussion of
loop tuning must be undertaken within the context of process and control
loop theory. With that in mind we would like to recommend to you a book
that covers this subject well: Fundamentals Of Process Control Theory, by
Paul W. Murrill, Instrument Society of America, Research Triangle Park,
NC, 1981, Second Edition 1991, ISBN 1-55617-297-4.
The HP E1415 Algorithmic Closed Loop Controller provides tuning
assistance in the form of the following loop control and monitoring features:
•
Manual control mode
•
Direct manipulation of variable values in both PIDA and PIDB.
•
PIDB operating values available from CVT
•
PIDB History Mode puts continuous sequence of operating values into
FIFO
The HP E1415's Status System allows you to quickly poll a single register
(the Status Byte) to see if any internal condition needs attention. Figure 3-11
shows that the three Status Groups (Operation Status, Questionable Data,
and the Standard Event Groups) and the Output Queue all send summary
information to the Status Byte. By this method the Status Byte can report
many more events than its eight bits would otherwise allow. Figure 3-12
shows the Status System in detail.
Questionable Data Group
Operation Status Group
Figure 3-11. Simplified Status System Diagram
Programming the HP E1415 for PID Control
Output
Queue
Status Byte
group summary bits
Standard Event Group
read with
*STB?
95
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