DynSignal('TextExpression')

Description

This function returns the value of the signal or expression specified by 'TextExpression'.

'TextExpression' must result in a text string that ibaAnalyzer can interpret as a new, valid expression. As a result, ibaAnalyzer then provides the signal that is derived by evaluating this expression.

A typical use case is the generation of a valid signal ID in the loaded data file, e.g. a signal ID consisting of [module number:signal number] for analog signals or [module number.signal number] for digital signals.

The function is used in particular in connection with the data point concept from the field of iba energy measuring technology. Various metadata is read, which is stored for each measuring point in structured form in the info area of the data file. The content of this metadata is the module number under which the corresponding measured value is stored in the data file.

This makes it possible to standardize the evaluation of measurement point data, even when the I/O configuration varies from system to system.

Example

In the analysis, the goal is to determine the calculated 10-second value of the frequency at a specific measurement point.

The module number under which this value is stored as a signal can be found in the metadata field:

MeasurementPoint.Frequency.SYS.10s

In the following example, the 10-second frequency value at measurement point 5 (MP5) is retrieved.

The measured value is stored in module 29, signal 0 in the data file, which corresponds to the ID [29:0].

The retrieval occurs in three steps, as reflected in the three rows of the signal table:

  1. Retrieval of the content of the info field MP5.Frequency.SYS.10s with the InfoFieldText function. The result "29" is temporarily stored as the text signal MP_Freq_Module (see top graph).

  2. To obtain the correct form of the signal specification, the ConCat function is used to combine the character "[", the text signal MP_Freq_Module and the characters ":0]" to form a string. The combined text is temporarily stored as the text expression Freq_Signal_Text (see second graph from the top). When specifying the signal number (here: ":0"), you can also use wildcards or enter ranges.

    • ":*" – all signals of the module

    • ":n-m" – signals from-to (e.g. ":20-29")

  3. Finally, the text expression Freq_Signal_Text is interpreted via the DynSignal function as a signal ID consisting of [module number:signal number] and its value is read out as the signal MySignal (see third graph from the top).

  4. This line displays the signal [29:0]. The value is identical to that of MySignal.