Waveform graph resetting during operation want to peak hold

[tanju]

Hello everyone,

I am currently working on data acquisition using a vibrometer in which I will conduct a frequency sweep using a signal generator to my DUT. I have an oscilloscope which I access through labview to get the input voltage and the laser output voltage which I demodulate and apply the appropriate filters. The problem here in the attached files (sorry I couldn't upload the files due to the size of the VI becoming so large so I attached pictures of the code), is that the right data comes through, however, my final waveform graph "Displacement (nm)" has two unknown outcomes. There is a case statement to keep the input voltage within a range (this is fine), I removed the pump to my vibration table to be fixed so sometimes I have an erratic one of signal that I use the second case structure if the magnitude is less than 0.2 nm than the signal is fine and to add to the waveform graph. However, if this condition occurs, then the write to graphs both stop as in "Front Panel.PNG" where it wont write to the graph the next time it operates. This is the first problem I am having anyone know the reason for this?

The other problem I am having is that when I increase the sampling time of my oscilloscope to obtain more frequency bins for the peak hold FFT to make the frequency response, is that the df value for example shifts like this 999.99, 999.98 and 1000 and this causes the graph to rest every time but as I said I want to keep the whole graph as this will build my frequency response of my DUT. You can also see this on the "Frontpanel.PNG" df = 9999.99 for that test, however, it can change to 10000 and the whole chart resets which is not what I want. I changed this manually in the cluster but this resetting still occurs. 

The problem is getting the data to build on the graph, I want to increase the sampling time of my experiment to get more bins to build a better FRF but these problems have now occurred

The hardware is a vibrometer attached to a teledyne lecroy 725zi-A and PC connected through LXI to labview and the LC oscilloscope drivers. The function generator is a R & S SML01 that I manually configure the sweep. I just access everything through the oscilloscope into labview

Any help you may have is most appreciated

Thanks,

Tanju

[datatechNDT]

Its a bit hard without the actual VI. Can you provide a picture of your false cases or they are just empty cases? If that is the case, as far as I understand is the resetting of the graph comes from the fact that you are using a waveform graph instead of a chart. Depending on your wanted behavior you can populate a chart or use a graph and provide a shifting register to keep track of previous iterations, also switching off the autoscale and programmatically updating it when needed might solve the issue when bin width changes, which essentially your bin width is your dx for the graph, aka multiple x property node.

[tanju]

Hi datatechNDT,

Firstly, I appreciate your response.

Yes the false cases are simply blank, I do not wish to add data to my graph. I have attached my VI this time and deleted out unnecessary parts to reduce the file size but the last waveform graph is still where the problem occurs. I was playing with the shift registers but how to get the clusters to combine and maintain the peak hold function? This is what I thought the peak hold function would do normally but it seems that changing df still resets everything or if I encounter an erratic signal it stops writing to the graph. I am using waveform graphs for everything not charts. I would prefer to keep the bin width the same and have the graph just continue the peak hold function and not to add data for the erratic signal and probably force the df values to always be the same. I tried this previously to force the same df but that didn't work.

Any help you have is most appreciated

Kind regards

[altenbach]

Please don not save your VI with 20MB+ of default data in the indicators!

[tanju]

Hi Altenbach,

thanks for your reply it is most appreciated.

I removed the data from the graphs before uploading the file so I am not sure what data is still in the file as I want to reduce the file size to upload the entire VI for some better help.

Kindest regards,

Tanju

[RavensFan]

You may have cleared the graphs, but you forgot to save the cleared graphs as the default values.  It is the difference between 22 MB in your VI which had data on the graphs when I opened it, and about 93 KB.

[tanju]

Hi Ravensfan,

Thank you for you kind reply. I apologise on my behalf for not having saved current settings.

I have re uploaded the complete file at 140 Kb now. Do you any advice going back to the original problems about the graph resetting or stopping? My thought is that the waveform graph should continuously obtain data as the program runs but this doesn't appear to be the case.

Have a merry Christmas and a happy new year

kindest regards,

Tanju