Response Electronics CL6011B Especificaciones descargar pdf (Pagina 275)

5Ć13Configuration Tips

Original Ć June 1990 CE4.2:CL6211

5.7.4 Operating Characteristics Of Override Control Loops

The override control system may exhibit some or all of the following

characteristics:

H If the upstream controllers are in Auto mode, and the signal selector

loop is changed from Man to Auto mode, the output may change by

a value equal to the largest deviation times gain value of the

upstream controllers. Since a signal selector, by definition, routes the

selected input value directly to the output while in Auto mode, the

output will change as a step function when the mode change occurs.

For instance, consider two loops which are tuned with a gain of 0.3

and reset of 20.0 repeats/minute. If both loops showed a deviation of

-20 percent with a low signal selector, then the mode change could

cause a change to the valve output value of -6.0 percent. (An error

of -20 multiplied by a gain of 0.3 = -6.0 percent.)

In addition, the valve output may be observed to change in steps

under these conditions, rather than moving smoothly through the

corrective range of action required by this process condition. This

stepping action in the valve output could continue until the PV for one

of the loops approaches SP.

This characteristic is only observed if both upstream controllers have

a deviation in the direction that would normally force the valve action

in the signal select direction (e.g., a negative deviation with a low

selector, or a positive deviation with a high selector).

H By design, proportional action will not have any affect on the output

of the overridden controller; thus, the overridden control loop will not

take over control until its PV crosses SP.

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Response Electronics CL6011B Especificaciones Pagina 275