Model: LC5296-AT /LC5248E-AT/LC5296V-AT masibus
Doc. Ref. no. : - m61C/om/301
Issue no. 13
User’s Manual Page 29 of 44
7.2 PID Control
AUTO TUNE FUNCTION:
Auto Tuning:
The Auto tuning process is performed at set point. Temperature will oscillate around the
set point during tuning process. Set a set point to a lower value if overshooting around
the normal process value is likely to cause damage. To start the auto tuning process, set
the desired set point, select the parameter A.TUN in TUNE menu and set it to YES.
During Auto tuning lower display (SV) will flash “AT” message.
After auto tune procedure is completed, the message will be removed and controller will
revert back to the PID control by using the new calculated PID values. The PID values
obtained are stored in the nonvolatile memory.
Control Parameter:-
Proportional BAND:
Proportional action is the action which the control output varies in proportion to the
deviation between the setting value and the processing temperature. If the proportional
band is narrowed, even if the output changes by a slight variation of the processing
temperature, better control results can be obtained as the offset decreases. However, if
when the proportional band is narrowed too much, even slight disturbances may cause
variation in the processing temperature, and control action changes to ON/OFF action
and the so called hunting phenomenon occurs. Therefore, when the processing
temperature comes to a balanced position near the setting value and a constant
temperature is maintained, the most suitable value is selected by gradually narrowing
the proportional band while observing the control results.
Integral Time:
Integral action is used to eliminate offset. When the integral time is shortened, the
returning speed to the setting point is quickened. However, the cycle of oscillation is also
quickened and the control becomes unstable.
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