Desin Instruments HS-7000 Series, General Instructions Manual

Page: 59 / 108

59
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Manual setting of the Positioner Course
If the valve is not provided with Feedback signal, or an Automatic calculationof the time course
in the calibration submenu is not required, manual setting of the time is allowed in the
Configuration menu.
Calculate manually the time the valve lasts to go from completely Open to completely Closed.
- For loop 1 enter in Configuration [do1] [ConF] and set in parameter [P 06] [nnnn] the time
of the valve course in seconds, from 1 to 1999 s.
- For loop 2 enter in Configuration
[do3] [ConF]
in the parameter
[P 06] [nnnn]
Important:
On the label of the motovalves the maximum time course is indicated, however, this can be
modified using limit contacts thus limiting the valve course, this is the time that should be
calculated and introduced in the parameter not the one indicated on the label.
MINIMUM PULSE SETTING:
The Minimum Pulse of these devices configured as for Step by Step, is used to define the
correction frequency of the pulses Open-Close sent to the motovalve, thus adjusting the
number of actions of the valve to the process without losing accuracy. Th eresult obtained in
this method is better than the one of the dead-band used in the old fashion controllers, since
this system does not produce control hysteresis.
The value of the Minimum Pulse defines the minimum variation in % of the controlled variable
so that the controller gives a new correction of the motovalve position.
This value can be set between 0 and 100%. The best results can be achieved using 1% (factory
setting) and 5%, with the recommended not to go over 10%, in function of the capability of the
actuator (of the valve) to actuate in short periods without damage.
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Minimum Pulse Settind.
- For loop 1 enter in Configuration [do1] [ConF] and set the Minimum Pulse value in parameter
[P 05] [nnnn]
- For loop 2 enter in Configuration [do3] [ConF] in parameter [P 05] [nnnn]
DEAD BAND:
The old fashion controllers were provided with a Dead Band, which is a symmetric band at the SP
(setpoint) in a way that, when the process variable is stable on the SP (within the dead band) the
controller does not generate any Open or Close pulses, thus avoiding the continuous action of
pulses to Open and Close. This system is not used in these models because, unlike the Minimum
Pulse system, produces lack of precision of the control igual to the amplitud of the Dead Band.
PID PARAMETERS SETTING:
The setting of the PID control parameters can be realized in Manual or Automatic modes, following
the same procedures explained in these instructions for a normal PID control including the Fuzzy-
Logic function.
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Derivative Action.
In a PID control, the Derivative action corrects the dynamic deviation of the process variable
over-acting on the actuator.
The classic Step by Step controllers are not provided with the Derivative action for the following
reasoning: The valve actuation response is slower than the one produced by Derivative action.
The Derivative action is available on the HS-7000 Series and can be used at any time
depending on the process requirements.