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Rockwell Automation 1746-BTM Barrel Temperature Control Module User Manual User Manual

Page 78

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Publication 1746-UM010B-EN-P - April 2001

9-10 Sample Program

The autotune abort bit O:1.12/2 must be turned off after an autotune
is aborted, if not the next time you try to enable an autotune it will
immediately be aborted. When you set bit O:1.12/2 high you must
also check that the autotune in progress bit I:1.8/11 is low. When that
happens reset the autotune abort bit O:1.12/2.

Figure 9.6 Correct way to abort an Autotune

TIP

Do not set the Autotuning enabled bits in the
output image table in the same scan that you set
the invoke autotune bit.

Do not perform M1 or M0 file transfers without
using the up/download request bits (output word
12 bits 12 thru 15) and the up/download request
ready bits (input word 9 bits 12 thru 15). These
bits must be used to insure block integrity.

When you need to disable a loop of control do
not just put a contact in front of the output TPO
bit. This will cause the PID loop to windup,
because the loop is still active and wants to
control. When you re-enable the loop, it will
oscillate about the setpoint then come into
control. The correct way to shut down a loop is
to put the loop into manual mode with 0% CV
output.