Response Electronics CL6011B Specifikace stáhnout pdf (Strana 47)

3Ć27 Theory of Operation: Point Processing

Original Ć June 1990 CE4.2:CL6211

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Monitored

Attribute

Deviation Limit

Deviation Alarm Cleared

Deviation Alarm Set

Deviation Alarm Cleared

Deviation Alarm Set

{

Deadband

Reference or

Set Point Value

Figure 3Ć11. Deviation Alarms

The deviation alarm equations are shown below:

The alarm is set if: PV >= ( SP + DTP ) or PV <= ( SP - DTP )

The alarm is cleared when: PV < ( SP + DTP - DB ) or

PV > ( SP - DTP + DB )

Where:

DB = deadband

DTP = deviation trip point

SP = set point

PV = process variable

Alarm D is a user defined alarm. It is implemented using the Function

Sequence Table (FST) Alarm Store (ALMST) function . 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. Refer to the FST section of the

Configuration Manual for details on the ALMST function.

3.3.3.3.2 Output Limiting

The output limiting function, which is available on all PCA types, is used

to prevent the IVP of a point from exceeding a configured high or low

limit. If the IVP value generated by the station function exceeds the

configured IVP high limit, then the IVP is set to that limit and the Valve

Output High (VOHI) alarm bit is set to a value of 1. If the IVP is less than

the configured IVP low limit, then the IVP is set to that limit and the Valve

Output Low (VOLO) alarm bit is set to 1. The VOHI and VOLO alarm bits

allow for operator indication at the console that either high or low output

limiting has occurred.

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Response Electronics CL6011B Specifikace Strana 47