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PA Module P03-01, Edition 09/2013
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P03-01_AdvancedLayout_R1309_en.doc
Acquisition and Storage of Curve Values
For the displayed course to reflect the actual course, the sampling rate of the process
value has to correspond at least to twice the change frequency of the process value. In
most cases, this requirement can be met with cyclical acquisition every 1s [2].
value has to correspond at least to twice the change frequency of the process value. In
most cases, this requirement can be met with cyclical acquisition every 1s [2].
In PCS 7, the sampling rate corresponds to the acquisition cycle of a process value. As
long as a process value is not archive, only the pre-history of the process value can be
displayed. By archiving a process value (refer to chapter P02-03) the history can be
displayed also, since archive variables are resorted to.
long as a process value is not archive, only the pre-history of the process value can be
displayed. By archiving a process value (refer to chapter P02-03) the history can be
displayed also, since archive variables are resorted to.
When curves are displayed, the pre-history differs from the history as shown in Table 1.
Table 1: Visible Differences between Prehistory and History [2]
Prehistory
History
Position of the time span
shown in the curve field
shown in the curve field
Always relative to the
present
present
Through an absolute point
in time and a selected time
span or through two
absolute points in time
in time and a selected time
span or through two
absolute points in time
Labeling of the time axis
Relative time indications; if
needed, can be switched to
absolute time indication
needed, can be switched to
absolute time indication
Absolute time indications
can be switched to time
indications relative to a
defined point in time of an
event
can be switched to time
indications relative to a
defined point in time of an
event
Updates
Curve is updated during the
display whereby all curve
points are shifted
display whereby all curve
points are shifted
Curve does not change
Value axis
The value axis is usually
located at the point in time of
the present (at the right
margin of the display)
located at the point in time of
the present (at the right
margin of the display)
The value axis is located on
the left margin of the display
the left margin of the display
Designing Curve Displays
In [2], guidelines for designing curve displays are provided. PCS 7 implements the basic
design details by default; for that reason, they are described here only briefly. There are
design rules, however, that you can implement yourself by means of the settings at OS
engineering. To do this in a specific way, a few details are introduced here.
design details by default; for that reason, they are described here only briefly. There are
design rules, however, that you can implement yourself by means of the settings at OS
engineering. To do this in a specific way, a few details are introduced here.
The curve display is displayed in the working area of the display area (refer to P02-01). It
consists of the title field, the curve labeling field, and the curve field. The title field should
contain the information for the unambiguous assignment to the process environment. In the
curve labeling field, it should be possible to read off the relationship of displayed the curve
and the process value. The curve display field is used to display the curve and should be
as large as possible. To implement the curve display field, the following information is
provided.
consists of the title field, the curve labeling field, and the curve field. The title field should
contain the information for the unambiguous assignment to the process environment. In the
curve labeling field, it should be possible to read off the relationship of displayed the curve
and the process value. The curve display field is used to display the curve and should be
as large as possible. To implement the curve display field, the following information is
provided.
To facilitate reading off the values, grid lines have to be available. The value axis in this
case should display several lines as an extension of the scale marks, and the time axis
several lines according to the current time grid. The number of grid lines should be low and
optically remain in the background. To this end, they should not be shown in color or blue.
Reading rulers can provide additional support.
case should display several lines as an extension of the scale marks, and the time axis
several lines according to the current time grid. The number of grid lines should be low and
optically remain in the background. To this end, they should not be shown in color or blue.
Reading rulers can provide additional support.