User Manual

CM2N8881en / 02.2000 Siemens Building Technologies
2/2 Landis & Staefa Division
In building automation and control, we primarily differentiate between physical and
virtual information points as shown in the following illustration based on two VISONIK
data points:
MW
RGB
°C
BPS
8881Z02E
P r o c e s s i n g
I/O module
HW
SW
Physical data point;
here: type MW
Virtual data point;
here: type RGB
Physical and virtual data or information points are defined as follows:
Designation Definition/Example
Physical information
points
Physical information points have transmitters in the plant. The
information is exchanged via I/O modules which represent the interface
between hardware and software. For this reason, VISONIK has named
them "I/O module points“.
Example above:
Measured value (MW) with temperature sensor in the plant. The latter
provides "raw measured value" information. Compare the previous
page.
Note:
Physical information points are also called real information points.
Virtual information
points
Virtual information points are software points or software data blocks.
They execute either logical or arithmetic operations such as open and
closed loop control, optimization and communication functions. They are
not connected directly to the I/O modules, but they can gather
information from I/O module points and assign calculated values to them
(processing).
Example above:
Controller block (RGB) with setpoint, controller parameters, etc.
Note:
Virtual information points sometimes are also referred to as
fictitious information points.
In VISONIK, a fictitious information point is a special type of virtual data point. By
setting a physical data point to "fictitious", the data point becomes a quasi-virtual data
point whose main value can be changed in terms of software. Application example:
Simulation of a measured value.
It is best to compile all information points of a project in a single list to serve as:
–
the basis for engineering, e.g. in the form of an information list containing all inputs and
outputs, basic and processing functions as per VDI 3814 (German standard), part 2.
–
the engineering result in the form of a data point list with the associated project and
system-specific information on each point.
Refer to the following documents for more information on this topic:
Document No. Title
CM2N8882E I/O module points
CM2B8301E BPS User’s Guide
Types of
information points
Physical and virtual
points
Definition and examples
Fictitious information
points
Information list and
data point list
Additional information
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2000 Siemens Building Technologies Ltd.