Response Electronics CL6011B Specifiche Scaricare il pdf (Pagina 45)

3Ć25 Theory of Operation: Point Processing

Original Ć June 1990 CE4.2:CL6211

The primary loop will perform normal PID control action when the

secondary loop is in the remote set point mode and the IVP of the

secondary loop is not output limited. When the IVP of the secondary

loop is output limited and a change in the primary loop's IVP will cause

the secondary loop to drive harder against its output limit, the integral

action will be disabled in the primary loop. This will prevent the primary

loop from winding up its output when the secondary loop is already

output limited in the direction the primary loop is tending to drive the

secondary loop.

3.3.3.3 Station Function Details

Station functions are items available for use with direct control points

(DCPs) that are configured to set up proper control of the process. Their

use depends on the requirements of the process. The details of these

functions are described in the following sections.

3.3.3.3.1 Alarm Processing

Each DCP is automatically configured with three standard alarms. Two of

these alarms (Alarm B and C) are absolute high/low alarms, the third one

(Alarm A) is a deviation alarm. These alarms are based on the process

variable and set point of the DCP. Two function sequence table (FST)

function blocks must be used to activate discrete outputs with the alarm

states. The desired alarm must first be loaded into the discrete signal

value using the Alarm Monitor Load (ALMLD) function (page 4

42). The

discrete signal is then directed to the discrete output using the Discrete

Output (DO) function (page 4

64). When the alarm is set, the

configured discrete output will be set to 1. When the alarm is cleared,

the configured discrete output will be set to 0. To obtain reverse logic, a

logical inverse (NOT) function (page 4

128) can be placed between the

ALMLD and DO functions.

In addition, alarm D is available as a user-defined alarm. It is

implemented using the Alarm Store (ALMST) FST function (page 4 44).

When the discrete signal value input to the ALMST function is a logic 1,

the alarm is set. When the discrete signal value input to the ALMST

function is a logic 0, the alarm is not set.

Absolute Alarms

Absolute alarms monitor the process variable of a point, and may be

individually configured as high or low alarms. If an absolute alarm is

configured as a high alarm and the value of the process variable goes

above the alarm trip point, then the alarm is set. When the process

variable falls below the level defined by the trip point minus the

deadband, the alarm is cleared.

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Response Electronics CL6011B Specifiche Pagina 45

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