It is easy to configure the OPC DataHub to bridge existing
points—just point and click. If necessary, you can
quickly configure linear
transformations and specify the direction of data flow
of the bridge. And should you want to create a new point
for a bridge, it's just few more clicks of the mouse. All
configuration and any changes are done on the fly, taking
effect as soon as you click the
4.2.1. Point-to-point configuration
- With the DataHub running, right click on the
OPC DataHub system-tray icon and choose
- In the Properties window,
select Bridging .
button. The Bridging Configuration window will
The three top panes in this window correspond to the
three basic steps in making the configuration: specify a
source, a destination, and any desired transformations.
The horizontal pane across the bottom shows the bridges
that exist on the system.
From the tree diagram in the
Source panel, select a source point
that you want to bridge.
For example, if you have the DataSim program running, you
can select the point Sine in the
DataSim data domain. The name of the
point gets automatically entered in the field at the top
of the panel. Alternatively, you can type the name of the
point in the entry field.
In the tree diagram in the
Destination panel, select a
When you select a destination point, its name gets
automatically entered in the field at the top of the
panel. Or you can type the name of a point in the
Specify direct copy or transformation.
Determine which direction you want the bridge to apply.
Select to change the
destination point when the source point changes, but not
change the source when the destination changes. Select
to change the source point
if the destination point changes, but not vice-versa.
Select both boxes for a
bidirectional bridge, where either point changes whenever
the other point changes.
Selecting the inverse direction will apply the
inverse of the transformation, as explained below.
- Click the button to
create and activate the bridge. The DataHub will create the
bridge and update the bridged points immediately.
In the bottom panel you can see all the bridges that
exist in the system, and the significant information about
If you click on a transformation, the source point,
destination point, and transform information get
displayed in their respective panels. Use the check box
at the front of each bridge to activate or deactivate
4.2.2. Making transformations
Specify the type of transformation by clicking one
of the three radio buttons:
transformations. It just copies the point.
multiply by one value and add another value, such as in the
equation y = mx + b where the destination point
is y, the source point is x,
the multiply by value is
m, and the then add value
is b. For example to transform a Celsius
source point to a Fahrenheit destination point, you would multiply
by 1.8 and add 32, or
Fahrenheit = (1.8 X Celsius) + 32
If you have selected the
direction for a transformation, you will get the inverse of the
transformation. In this example, you would get a conversion from
Fahrenheit to Celsius, or the results of this equation:
Celsius = (Fahrenheit - 32) / 1.8
As an alternative to entering transformation values, the
DataHub also offers Linear Range Mapping.
lets you enter a
range for the source and destination, and the DataHub automatically
calculates the corresponding linear transformation. For example,
to create the same Fahrenheit to Celsius transformation, you could
use the defaults of 0 and
100 for the Min and
Max of the source point. Then you would
enter 32 and 212 for the
Min and Max of the
destination point. As soon as you make these entries, the correct
values get entered automatically in the Linear
When you use linear range
mapping, you can limit the transformed value to the maximum and
minimum by checking the boxes. The
clamps get applied to the point being changed, ie. to the
destination point for forward direction, to the source point for
inverse direction, and to both points for bidirectional
If you want to save this transformation for future
use, click the button at
the top of the Transformation panel, and enter a name in
the box that pops up.
Once stored, the transformation will become
available by name in the drop-down list.
To load a transformation, simply select its name from the
Copyright © 1995-2010 by Cogent Real-Time Systems, Inc. All rights reserved.