Future Design MCT-CM, User Manual

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MCT-CM
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Pressing the
Set button allows the user to adjust the loop set point without having to leave the tuning screen in
order to observe the control response.
Pressing the
AT button allows the user to activate/deactivate the loop auto tuning feature. When auto tune is
active, the indicator on the button will be illuminated. In addition, the process value of the loop on the Loop
view screen will flash while auto tune is active. This allows the user to activate auto tune and then return to the
main Loop view screen to observe system operation while being informed of the loop auto tune status.
NOTE: When manually entering new tuning values, it may take several seconds for the new entry to be shown
as the values have to be written and saved to the loop control selected for tuning.
9.11.1 Heat/Cool (Bimodal) Control
When a loop is programmed for heat/cool operation, the values of the Cooling PB and Dead Band affect the
way the heat and cool outputs work together to control the process.
The Cooling PB is measured in % of the proportional band with a range 1-255. Set cooling PB to 100% to
begin and examine the cooling effect. If cooling action should be enhanced then decrease the cooling band. If
cooling action is too strong then increase the cooling band. The value of the cooling proportional band is related
to the heating proportional band and its value remains unchanged throughout any auto tuning procedures.
NOTE:
The adjustment of the Cooling PB is also related to the cooling media used. When air is used as the
cooling media, it is recommended that the Cooling PB be set to 100%. For oil, a typical setting to use
for the Cooling PB is 125%. If water is used as the cooling media then adjust the Cooling PB to 250%.
The adjustment of
Dead Band is more dependent upon system requirements. If more positive values of dead
band (greater dead band) are used, an unwanted cooling action can be avoided but an excessive overshoot
may occur. If more negative values of dead band (greater overlap) are used, an excessive overshoot can be
minimized but an unwanted cooling action may occur.
Dead band is adjustable in the range of -36.0% to 36.0 % of the heating proportional band. A negative dead
band value provides an overlap between heating and cooling action in which both outputs can be active at the
same time. A positive dead band value provides a dead band area in which neither output is active around set
point.