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7.5
Determining the Process Characteristics ....................................................................... 359
7.6
Setting Tuning Loop Gains .................................................................................................. 360
7.6.1
Basic Iterative Tuning Approach ...................................................................................................................... 360
7.6.2
Setting Loop Gains Using the Ziegler and Nichols Tuning Approach ................................................ 361
7.6.3
Ideal Tuning Method ............................................................................................................................................. 362
7.7
PID Example ........................................................................................................................... 363
7.7.1
Reference Array Initialization using %M00006 .......................................................................................... 363
Chapter 8 Structured Text (ST) Programming .................................................................................... 365
8.1
Language Overview .............................................................................................................. 365
8.1.1
Statements ............................................................................................................................................................... 365
8.1.2
Expressions .............................................................................................................................................................. 365
8.1.3
Operators .................................................................................................................................................................. 366
8.1.4
Structured Text Syntax ........................................................................................................................................ 367
8.2
Statement Types ................................................................................................................... 368
8.2.1
Assignment Statement ....................................................................................................................................... 369
8.2.2
Function Call ............................................................................................................................................................ 370
8.2.3
RETURN Statement ............................................................................................................................................... 373
8.2.4
IF Statement ............................................................................................................................................................ 374
8.2.5
CASE Statement ..................................................................................................................................................... 375
8.2.6
FOR ... DO Statements.......................................................................................................................................... 377
8.2.7
WHILE Statement .................................................................................................................................................. 379
8.2.8
REPEAT Statement ................................................................................................................................................ 380
8.2.9
ARG_PRES Statement .......................................................................................................................................... 381
8.2.10
Exit Statement ........................................................................................................................................................ 382
Chapter 9 Diagnostics ............................................................................................................................... 383
9.1
Fault Handling Overview ..................................................................................................... 384
9.1.1
System Response to Faults ............................................................................................................................... 384
9.1.2
Fault Tables .............................................................................................................................................................. 384
9.1.3
Fault Actions and Fault Action Configuration ............................................................................................ 385
9.2
Using the Fault Tables ......................................................................................................... 386
9.2.1
Controller Fault Table .......................................................................................................................................... 386
9.2.2
I/O Fault Table ......................................................................................................................................................... 388
9.3
System Handling of Faults .................................................................................................. 390
9.3.1
System Fault References .................................................................................................................................... 391
9.3.2
Using Fault Contacts ............................................................................................................................................ 394
9.3.3
Using Point Faults .................................................................................................................................................. 396
9.3.4
Using Alarm Contacts .......................................................................................................................................... 396
GFK-2950C
February 2018
Contents
ix
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