D2-5
IM 34M06H62-02E 2nd Edition : June 2008-00
(4) Output does not respond to or follow a changed set point
value
- Does the control set point (CSP) change with the set point (SP)? If not, check
whether the SP Up Gradient (SPR.UP), SP Down Gradient (SPR.DN) and SP
Gradient Time Unit (SPR.TM) parameters have been specified inadvertently. Setting
the SP gradient parameters will slow down the response of the CSP.
- Is the output type of the loop correctly selected? Is the wiring to a controlled load
correct? Is an external 24 V DC power supply connected to the module? Remember
that an output from the module requires an external power supply to drive the load.
- Does the output change with SP? If not, check the value of the control output
parameter (HOUT or COUT). Also check the values of the Output Type Selection
(OUTPUT), Output Terminal Selection (OUTSEL 1-4), and Forward/Reverse Switch
(DR) parameters. Remember that output is either 0 or 100% in ON/OFF control
mode.
- If the above measures still fail to solve the problem, see (1), "Input does not change,
or fluctuates excessively" given in this chapter.
(5) Excessive overshooting
- Is the overshooting suppression function "Super" enabled? If not, enable it and check
if the problem disappears.
- If "Super" is enabled, disable it by setting SC to 0 to see if the problem disappears.
Sometimes, "Super" may increase instead of reduce overshooting when PID
parameter values are inappropriate.
- Try to suppress overshooting by adjusting the PID parameters as described in
Section C6.5, "Manual Adjustment of PID Constants."
- If the above measures still fail to solve the problem, replace the loop and repeat the
troubleshooting steps. If you have a spare module, replace the module and repeat
the troubleshooting steps.
(6) Settings are not enabled
- Controller parameters and I/O parameters (input and output types, input range, and
PV range) must be enabled before their setting can take effect. For details on how to
enable parameter settings, see Section B2.3, "How to Enable Settings."
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