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5Ć11Configuration Tips

Original Ć June 1990 CE4.2:CL6211

5.7.2 Use Of Filtering In Override Control On Loops With

Significantly Different Dynamic Characteristics

For loops with significantly different dynamic characteristics, the loop

with the fastest" reset (largest number of repeats per minute) should be

used to determine the filter time constant. Aside from this, these loops

should make use of track value filtering as previously described. The filter

time constant is tuned to a value equal to the reciprocal of the reset

action used in the fastest" upstream controller.

For example, consider two loops acting in an override control system,

where the loops are tuned as follows:

Loop 1

Gain = 0.4

Reset = 30.0 repeats / minute

Rate = 0.0

Loop 2

Gain = 0.5

Reset = 4.0 repeats / minute

Rate = 0.0

The user must filter the tracking value with a first order filter having a time

constant of 1/30.0, or 0.033 minutes. The DCPs FST must be configured

to provide the filtering action.

5.7.3 Use Of Filtering For Override Control On Slow Loops

If override control is used on a process which exhibits very slow dynamic

response, the filtering action can affect the controller output tracking

when the loops are in Manual mode. The affect can be prevented by

disabling the track value filter.

Typically, the filter should be reset to the output of the signal selector

loop whenever the signal selector is in the Manual mode. This will force

the output values of the upstream controllers to track the value of the

signal selector loop whenever the operator is manually adjusting the

valve position.

For slow loops with significantly different dynamic characteristics, the

loop with the fastest" reset (largest number of repeats per minute)

should still be used to determine the filter time constant. Aside from this,

these loops should make use of track value filtering as previously

described. The filter time constant is tuned to a value equal to the

reciprocal of the reset action used in the fastest" upstream controller.

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Response Electronics CL6011B Spezifikationen Seite 273