Point links are used to update target points based upon the value of source points. They keep two points in "sync", according to an optional transformation formula that can be defined. Practically speaking, point linking can be used to read the values in one system (from one or more data sources) and immediately set the values in another system (to one or more data sources).
Point linking can also be achieved by using a change or update event detector on source points, and then creating an set point event handler for each to have the value set in a target point. However, point linking serves this purpose better for a few reasons:
Note: point links can be set up such that infinite loops of setting can occur. Scada-LTS will detect such loops at runtime, stop the propagation, and raise a recurrsion failure event.
To add a new point link, click the icon. To edit an existing link, click the link's
description in the "Point links" list.
The Export ID is the value used to identify the point link across multiple Scada-LTS instances. It is used by the Import/Export facility. This value must be unique among point links. A unique and random value is automatically generated, but it can be changed to be more intuitive.
The Source point is the point that will be monitored for value. It is the point from which values come.
The Target point is the point that will be set with values. It is the point to which values go.
The Script is an optional value that will transform the source value as necessary. More information on
scripting can be found in the Meta point properties documentation. The context variable name is "source". So, a
script such as "return source.value / 2;" will set the target point with half the value of the source point. Note that
data type transformations can also be done, such as "if (source.value > 0) return true; return false;", which would
convert a numeric source value to a binary target value. Use the icon to validate your
script (the source point must be available).
Event determines if the target point is set whenever the source point is updated (i.e. receives a new timestamp but not necessarily a new value), or only when it is changed (i.e. receives a new timestamp and value).
A point link can be Disabled so that it does not run. This can be useful if you do not wish to delete the link, but also do not currently want it enabled.
To save a point link, click the icon at the top right. To delete an existing link,
click the
icon.