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ES - SIMATIC Manager -- Creating programs -- CFC - Using block libraries
What are the system requirements for using SIMATIC PCS 7 Industry Library?
What should you watch out for when changing the symbolic addresses of input/output modules?
Why are the inputs of the driver block in the CFC chart no longer interconnected after replacing a HART analog module?
How do you parameterize the PCS 7 APL channel driver so that the output process value is inverted?
How do you configure a Modbus slave using the "RCV_341" (FB 121) PCS 7 block?
Why do I get the signal "QBAD" on my "CH_AI" driver block?
How do you configure the "Sample_T" input?
Why is the module INT_P issuing invalid values at the output?
Why isn’t the CH_AI block not interconnected automatically with the option "Create module driver"?
How can I change the preset message class in standard blocks?
Can blocks from the CFC library for the S7-300 CPUs also be used in a program for an S7-400 CPU?
What is the meaning of the block input VALUE_QC of the CH_DI block?
Why is the simulated value not output on the CH_AI driver block and how can a value still be simulated?
When do you speak of a "self-regulating process" and when of a "non-self-regulating process"?
How do you do perform controller optimization with the PCS 7 PID tuner?
What is the meaning of the parameters "GAIN", "TN" and "TV" with the CTRL_PID block?
Why is there only half the expected current output from each of the analog output modules in the case of redundant modules?
How much memory is used by the SIMATIC PCS 7 V6.0 library blocks and templates in the PLC?
What do I have to take into account to avoid that the actual value overshoots when switching over from hand/track operation to automatic operation of the "CTRL_PID" with activated setpoint ramp?
How can additional message texts - only as event and OS range - be edited in a block that supports messages in SIMATIC PCS 7 V5.x?
When generating the module drivers, how can you clear the message "Necessary files are missing for block CH_AI. Please note that you must install exactly that version of the library from which this block was imported"?
Why does the CH_AI driver report the slave still to be defective (QBAD=1) after failure and return of a PROFIBUS DP slave (e.g. ET 200M)?
How do you interconnect an FM350-2 in PCS 7?
How can you clear the error message "Value BITVAL is not defined in file AL_CHN.xml / CH_DI." in the module driver log?
How do you configure the "Sample_T" input?
Part number:

Description
The "Sample_T" input can be found on blocks DIF_T, CTRL_PID and PT1_P among others. These blocks have one thing in common: they simulate the behavior of continuous transfer elements. The input/output signal behavior of these transfer elements is defined by parameters such as TN, TV and GAIN.

Processing in digital computers however is time discrete. This means that calculation of the transfer behavior takes a finite time or is only done at discrete intervals. This time is not negligible and it is imperative to include it in the calculation. This is what the "Sample_T" input is for. You use this input to inform the block of the time base used to call it.
Always call these blocks in a cyclic interrupt OB. Only there will the block be processed in a cycle of constant duration and you can specify the cycle time of this cyclic interrupt OB directly at the "Sample_T" input parameter.

In PCS 7 V4.0x you must determine the calling cyclic interrupt OB and specify the cycle time configured for this OB at the "Sample_T" input.

As from version V5 of PCS 7 the "Sample_T" input is automatically parameterized with the correct sampling time if this has been selected in the "Compile" dialog. The CFC recognizes this from the system attribute "S7_sampletime = 'true' " at the "Sample_T" input parameter.


Fig. 01

As from version V7 of PCS 7 the "Sample_T" input is parameterized automatically each time you compile.

Warning:
Do not use the "Sample_T" parameter to change the I/O behavior of the transfer element. Only ever use the parameters provided for that purpose.

 Entry ID:5505008   Date:2010-06-28 
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