How can I export complex FRF data in ASCII files especially UFF58 format?

[pwb]

Background:

I have a problem saving analysed data into a format that another software program (MODENT) can import.

I am using "SVA_Impact TEST (DAQmx).seproj", to acquire force and acceleration signals from a SISO hammer model test, and process up to the stage of an FRF and coherence plot. I need to export the FRF information into MODENT, meaning it must contain both magnitude and phase (real and complex) information in one file. (MODENT does not need the coherence information, which is only really used during the testing process to know we have good test data. The coherence information can already easily be saved into ASCII text file, and kept for test records - not a problem).

MODENT is a speciaised modal analysis package, and the FRFs from tests can be imported into its processing environment using its "utilities". The standard is a UFF58 file containing the FRF information.

Labview does not seem to be able to export the FRF data in UFF58 format. In general, Labview can export to UFF58, but only the real information, not the complex information - is this correct?

Is there a way to export the real and complex information from FRFs using one file.

I am working on this problem from both ends:

1. MODENT support, to help interface into MODENT.

2. Lavbiew support, to try to generate an exported file format with all necessry analysed data.

[DiscoBall]

Hi pwb,

It looks like you are using the Sound and Vibration Toolkit in SignalExpress. Did you import that project into LabVIEW, or are you still in your SignalExpress project?

If you are in LabVIEW, are you using the UFF58 File VI's like SVT UFF58 Open File.vi? Or, are you using the DataPlugin VIs? Please let me know so we can offer the best support possible.

[pwb]

Hi

I started with "SVA_Impact Test (DAQmx).seproj".

This is good because:

-all settings for the sensors are easily defined, including verification of internal excitation current.

-a useful environment for simple test practise, then use of the "advanced" environment for actual tests.

-can use/edit time and load limits.

Problem: as descirbed with exporting/saving all FRF information (minimum must be real and complex data for the FRF magnitude and phase [not phase unwrapped], other data like cohernece etc is also good) in a single suitable file (UFF58 preferred) for import into MODENT.

Then I found out the UFF58 problem is due to using Signal Express, so found "SVXMPL_Impact Test (DAQmx).vi". I understand full Lbaview (VIs) can have real and complex data exported/saved to UFF58. This would need to be added into this VI.

The problem now for me, is that:

-Do not have the functions of time and load limits.

-Many settings are embedded, and not as accessable as for the SE.proj version.

For example, using this versions, creates arrors stating the excitation current is incompatable. I have added some graphical code in the block diagram, but it does not automatically sense the settings needed. This applies to various settings that it would be useful to access.

[Jason_D]

pwb,

What do you mean by "Do not have the functions of time and load limits."?

In going from Signal Express to LabVIEW have you tried using the conversion from Signal Express to LabVIEW VIs?  Tools»Generate Code»LabVIEW Diagram

What excitation current are you using in LabVIEW?  Would you mind posting your code so that I can see what you are dealing with.  What other settings are you looking to access?

[pwb]

Hi

Have a look at the "seproj" and "vi" versions I mentioned in this thread - both available from the supplied example VIs in Signal Express and Labview. I've also attached these here.

The "seproj"version has what are called "limits" for the input data, meaning it cheks certain criteria to make sure the test data sentfor analysis (to give the FRF) is wihin certain limits: 1. "overload" where the amplitude must be below a set maxiumum, 2. "time", where the signal must deacy to zero within the time envelope. These are useful test check functions to have.

I looked at the conversion from SE to Labview VIs, but if I understand correctly, this essenetially embeds the SEproject in Labview, but does not allow the same use of viewing of the user windows during testing (eg seeing the overload plots, editing the overload levels, etc)?

Other settings:

-signal input range, sensitivity, Iex source, Iex value, dB reference, No. of samples and sample rate.

-triggering off the hammer, with all the setting optons shown in step setup for "trigger"

-all settings associated with the load and time limits; presented in a very useful format of either defining by X,Y coordinates, or by scalling.

-all config and averaging options for the freqency response.

The practise envirnoment in the SEProj version is also useful, as getting the technique right for using the hammer is not always easy, and it allows a quick check of basic settingsbefore doing the actual tests.

The Nyquist plot in the VI version is useful.

Happy New Year to everyone !

[Jason_D]

pwb,

There is a Limit Test Express VI in labview that does the same thing.  Or you can use the lower level VIs like Limit Testing or SVL Limit Testing.

For setting the range if you look at the block diagram you will see 400 and -400 going into the top of the DAQmx Create Channel VI this is where you can change the range in addition to the other things you mentioned like sensitivity, Iex source, Iex value, dB reference, (No. of samples and sample rate on the DAQmx Timing VI).

You can certainly use controls to configure a setup that would be an easy to use interface like signal express.  In the end labview can do all the same things they just might take a little more work and not be premade.