Response Electronics CL6011B Dokumentacja Pobierz pdf (Strona 46)

3Ć26 Theory of Operation: Point Processing

Original Ć June 1990CE4.2:CL6211

Similarly, if an absolute alarm is configured as a low alarm and the value

of the process variable goes below the trip point, then the alarm is set.

When the process variable increases above the level defined by the trip

point plus the deadband, the alarm is cleared. Figure 3Ć10 illustrates the

relationship between the process variable, the alarm trip points and the

deadband.

100%

Monitored

Attribute

High Trip Point

Low Trip Point

Low Alarm Cleared

Low Alarm Set

High Alarm Cleared

High Alarm Set

{

Deadband

Figure 3Ć10. Absolute Alarms

The absolute alarm equations are shown below:

The alarm is set if: PV >= HTP or PV <= LTP

The alarm is cleared when: PV < ( HTP - DB ) or PV > ( LTP + DB )

Where:

DB = deadband

HTP = high trip point

LTP = low trip point

PV = process variable

Deviation Alarm

A deviation alarm is triggered when the absolute value of the difference

between the process variable and the set point exceeds the value of the

deviation alarm trip point. The deviation alarm is cleared when the

absolute difference between the process variable and the set point is

less than the value of the deviation alarm trip point minus the deadband.

Figure 3Ć11 shows the points at which the deviation alarm is set and

cleared.

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 319 320

Brak uwag

Response Electronics CL6011B Dokumentacja Strona 46