SCADA Trending Pen with Dynamic Tag
Ecava IGX SCADA allows you to dynamically turn on/off a pen from display during run-time. And there’s no restriction in any form except your database size. Obviously we don’t save all tags to avoid your database grows to reach disk limit in no time. However, you may have some situations that want to allow operator to choose any tag to trend during run-time, which is not hard to achieve in 3 steps:
- You need to create some buffer tags in advanced that log in your desired frequency. e.g. buf001, buf002 & buf003, which is of float datatype.
- Then create the same numbers of input fields on the screen which allow operator to enter any tag name during runtime into source tags: src001, src002 & src003, which is of string datatype.
- Lastly you need to have a back-end script that trigger at the same frequency like the logging rate, whereby consist of the following lines:
setTag( 'buf001', +getTag( getTag( 'src001')));
setTag( 'buf002', +getTag( getTag( 'src002')));
setTag( 'buf003', +getTag( getTag( 'src003')));
Note that the first or inner getTag() is to fetch the tagname that entered dynamically by operator during runtime. Then the second or outer getTag() is to get the tag values of the tagname specified by operator. And the plus operator in front of getTag is a shortcut to ensure the returned data is of number type.
The concept behind is straightforward. Firstly create some buffer tags that constantly logging into database with your desired trending rate. Secondly, you list down some interested tag names for operator to trending. Then allow them to specify any tag during run-time. Lastly the script keeps getting the values of the specify tag name and write into the buffer tags that constantly being logged.
Please contact support in case you are not clear.