The Measurement Explorer is the centerpiece of the Manage Measurement Task. It literally allows to explore and manage the measurements inside the project. Therein the user can create different test setups, measurement channels, edit the measurements and assign their properties.
Hereafter some properties of the Measurement Explorer, and the connected windows, in the context of Experimental Modal Analysis (EMA) are outlined.
Defining the EMA testing type
Three types of the EMA testing type depending on the location of input/output sensors are distinguished in ARTeMIS, that is
- fixed output/rowing input (output sensors are fixed, input sensors are moving),
- rowing output/fixed input (output sensors are moving, input sensors are fixed),
- rowing output/rowing input (both output and input sensors are moving).
When the accelerometer is roving, a column of the FRF matrix, corresponds to the response of the structure at different output sensor locations. This is theoretically equivalent to the response of the structure to the roving inputs, when the output locations are fixed.
In practice, however, roving the input has some advantages over roving the accelerometer. When moving accelerometers, one has to allocate the sensors at the different measurement points. This alters the mass distribution on the structure, which could then alter its modal parameters. Moving the inputs, however, is also not completely without any consideration. Since the input is usually considered as a one channel and an accelerometer can measure output is three directions, one should excite the structure in multiple locations to ensure the resulting mode shapes are complete.
The aforementioned type of EMA test can be selected from the Properties window, as illustrated below
Defining the type of EMA input/output measurements
The Measurement properties allow to define the type of EMA input/output measurements:
- hammer/shaker inputs,
- acceleration/velocity/displacement outputs
as illustrated below
Viewing and disconnecting measurements from the analysis
In the Data Organizer, besides the usual checkbox's for showing the raw channel data, there is an Input Average folder in which all of the individual inputs are stored. Selecting/Highliting an input (here an impact) will show the underlying data (both inputs and outputs) for the corresponding input in all checked channels.
An input with a checked checkbox means that the input is enabled and will be used in the analysis. For the hammer input, the hammer icon in this case is green. Unchecking an input will disable it, that is exclude it from the further analysis, resulting in the hammer icon turning red.
An input can also be completely deleted from the project by using the delete button in the Data Organizer toolbar.