In WinCC OA
it's possible to individually create device orientated data points.
The basic concept of such a structured data point was introduced
in the section Data point Concept,
Process Image. In the following sections the practical use
of data points combined with detailed background information will
be provided.
In order to work with WinCC OA
and to be able to create user interfaces for the use, the carrier of the presented information
must be defined. These carriers are variables whose values present
the current process information. Such process
variables are called data
point elements in WinCC OA.
In order to display existing data points or to
create new ones, you usually use the database
editor PARA. It can be opened with the already opened graphic
editor GEDI using the
symbol.
Figure: Database Editor PARA
Alternatively, we could also define the database
editor as an own manager in the console and start it from the
console. Therefore, open the manager selection dialog (see figure
on the page Configuration
of a Project) through the button, select the entry WCCOAui and enter the parameter
"-m
para" in the "Options" field. Consider that the restart option is set
to "manual".
Data point types
The list in the field on the left side (in the
figure above) shows all data
point types available in the current project. Each of these
data point types represents a whole class of devices
or logical units. If you click on the "+" sign
in front of the name of the data point type, a list of data
points (instances/devices) of this type will be shown.
A data point type
is a form of template for structured data points. Structure, naming
and partly also configurations are already configured when defining
the type.
Figure: Data point Type "PUMP1"
as a Template of a whole Class of Devices
CAUTION
Before it's possible to create
a structured data point as a representative of a device, a corresponding
data point type has to be created as a template.
Data points
Each data point
can represent a real device
or a logical combination of information.
It is built up of one or several, almost arbitrary structured
data point elements. Each
data point belongs to its data point type and is accordingly shown
in the module PARA. A double click on the name of the data point
type or the "+" symbol in
the front of the name opens a list of all data points of one type.
The following image shows two
types available by default
and their data points (instances). The data point type ExampleDP_Float has
4 data points (instances) in this case. This data point type consists
of only one
data point element
and can therefore only represent a single process variable. This
corresponds to the common data model of the most SCADA systems
but is an exception in WinCC OA.
This type (and also the other ExampleDP*
types) are merely available for test
or demonstration purposes.
Figure: Existing Instances of the
Data point Types ExampleDP_Float and PUMP1
The data point
type PUMP1 (displayed at the right) corresponds more to
the common structure in WinCC OA.
Numerous process variables are part
of the device-oriented data point. At the start, PUMP1
has just a single data point instance. Even this is an exception:
it is a master data point (MP)
that can display certain configuration information for the type.
The master data
points will be described later. There are no real data point
instances available for the type PUMP1
since this is a new, initially empty project.
Figure: Database Editor PARA -
Data point Type ExampleDP_Float with data point ExampleDP_Arg1
NOTE
Data point types and data points only exist
within a project. Each of the projects on a computer can have
other data point types and data points even with the same names.
In order to transfer existing data point types and data points
from a project to another one, the Import/Export
function of the ASCII manager is used. For more information, see
ASCII
Manager Panel, basics.
Information
at the data point element
Each data point element primarily represents the value of a process variable,
however there is some important additional information about this
value. It's a complete process
image since it maps all
the essential attributes
of a recorded value.
Figure: Information
on the data point Element - Value with Attributes (Time, Quality,
Origin)
These additional attributes of the value could
also be seen in the database editor PARA. Additionally, you can
see that there are two different
fields for value display.
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