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130
Creating and Running Custom Algorithms
When the process value reading reaches 140 the "error term" would equal
zero so the value sent to the digital output would be 0 (heater off). Fine so
far, but as the bath temperature coasts even minutely above the setpoint, a
small negative value will be sent to the digital output which represents a
boolean true value. At this point the output will again be 1 (heater on) and
the bath temperature will continue go up rather than down. This process is
now out of control!
Modifying the
Standard PIDA
This behavior is easy to fix. We’ll just modify the standard PIDA algorithm
source code (supplied with your HP E1415 in the file PIDA.C) and then
define it as a custom algorithm. Use the following steps.
1. Load the source file for the standard PIDA algorithm into your
favorite text editor.
2. Find the line of code near the end of PIDA that reads:
outchan = Error * P_ I_out + D_factor * (Error - Error_old)
and insert this line below it:
if ( outchan <= 0 ) outchan = 0; /* all value not positive are now zero */
3. going back to the beginning of the file change all occurrences of
"inchan" to the input channel specifier of your choice (e.g. I100).
4. As in step 3, change all occurrences of "outchan" to the digital output
channel/bit identifier of your choice (e.g. O108.B0).
5. Now save this algorithm source file as "ONOFFPID.C".
Algorithm to Algorithm Communication
The ability for one algorithm to have access to values from another can be
very important particularly in more complex control situations. One of the
important features of the HP E1415 is that this communication can take
place entirely within the algorithms’ environment. Your application program
is freed from having to retrieve values from one algorithm and then send
those values to another algorithm.
Communication
Using Channel
Identifiers
The value of all defined input and output channels can be read by any
algorithm. Here is an example of inter-algorithm channel communication.
Implementing
Multivariable Control
In this example, two PID algorithms each control part of a process and due
to the process dynamics are interactive. This situation can call for what is
known as a "decoupler". The job of the decoupler is to correct for the
"coupling" between these two process controllers. Figure 4-3 shows the two
PID controllers and how the de-coupler algorithm fits into the control loops.
As mentioned before, algorithm output statements don’t write to the output
Содержание VXI 75000 C Series
Страница 2: ......
Страница 16: ...16 ...
Страница 18: ......
Страница 30: ...30 Getting Started Chapter 1 Notes ...
Страница 32: ...32 Field Wiring Chapter 2 Figure 2 1 Channel Numbers at SCP Positions ...
Страница 44: ...44 Field Wiring Chapter 2 Figure 2 11 HP E1415 Terminal Module ...
Страница 54: ...54 Field Wiring Chapter 2 Notes ...
Страница 61: ...Programming the HP E1415 for PID Control 61 Chapter 3 Programming Overview Diagram ...
Страница 124: ...124 Creating and Running Custom Algorithms Chapter 4 Figure 4 2 Algorithm Operating Sequence Diagram ...
Страница 136: ...136 Creating and Running Custom Algorithms Chapter 4 Notes ...
Страница 152: ...152 Algorithm Language Reference Chapter 5 Notes ...
Страница 304: ...304 HP E1415 Command Reference Chapter 6 Command Quick Reference Notes ...
Страница 308: ...308 Specifications Appendix A Thermocouple Type E 200 800C SCPs HP E1501 02 03 ...
Страница 309: ...Specifications 309 Appendix A Thermocouple Type E 200 800C SCPs HP E1508 09 ...
Страница 310: ...310 Specifications Appendix A Thermocouple Type E 0 800C SCPs HP E1501 02 03 ...
Страница 311: ...Specifications 311 Appendix A Thermocouple Type E 0 800C SCPs HP E1509 09 ...
Страница 312: ...312 Specifications Appendix A Thermocouple Type E Extended SCPs HP E1501 02 03 ...
Страница 313: ...Specifications 313 Appendix A Thermocouple Type E Extended SCPs HP E1508 09 ...
Страница 314: ...314 Specifications Appendix A Thermocouple Type J SCPs HP E1501 02 03 ...
Страница 315: ...Specifications 315 Appendix A Thermocouple Type J SCPs HP E1508 09 ...
Страница 316: ...316 Specifications Appendix A Thermocouple Type K SCPs HP E1501 02 03 ...
Страница 317: ...Specifications 317 Appendix A Thermocouple Type R SCPs HP E1501 02 03 ...
Страница 318: ...318 Specifications Appendix A Thermocouple Type R SCPs HP E1508 09 ...
Страница 319: ...Specifications 319 Appendix A Thermocouple Type S SCPs HP E1501 02 03 ...
Страница 320: ...320 Specifications Appendix A Thermocouple Type S SCPs HP E1508 09 ...
Страница 321: ...Specifications 321 Appendix A Thermocouple Type T SCPs HP E1501 02 03 ...
Страница 322: ...322 Specifications Appendix A Thermocouple Type T SCPs HP E1508 09 ...
Страница 323: ...Specifications 323 Appendix A 5K Thermistor Reference SCPs HP E1501 02 03 ...
Страница 324: ...324 Specifications Appendix A 5K Thermistor Reference SCPs HP E1508 09 ...
Страница 325: ...Specifications 325 Appendix A RTD Reference SCPs HP E1501 02 03 ...
Страница 326: ...326 Specifications Appendix A RTD SCPs HP E1501 02 03 ...
Страница 327: ...Specifications 327 Appendix A RTD SCPs HP E1508 09 ...
Страница 328: ...328 Specifications Appendix A 2250 Thermistor SCPs HP E1501 02 03 ...
Страница 329: ...Specifications 329 Appendix A 2250 Thermistor SCPs HP E1508 09 ...
Страница 330: ...330 Specifications Appendix A 5K Thermistor SCPs HP E1501 02 03 ...
Страница 331: ...Specifications 331 Appendix A 5K Thermistor SCPs HP E1508 09 ...
Страница 332: ...332 Specifications Appendix A 10K Thermistor SCPs HP E1501 02 03 ...
Страница 333: ...Specifications 333 Appendix A 10K Thermistor SCPs HP E1508 09 ...
Страница 334: ...334 Specifications Appendix A Notes ...
Страница 346: ...346 Glossary Appendix C Notes ...
Страница 388: ...388 Generating User Defined Functions Appendix F Notes ...
Страница 438: ...438 Index Writing the algorithm 129 values to CVT elements 120 values to the FIFO 121 Z ZERO CALibration ZERO 194 ...