Timebase plot flickers using SV measurement suite

[m_tahir_m]

Hello everybody,

I am using sound and vibration measurement suite v7.0 trial with PCI-6143. I modify the example program for plotting orbit and timebase plot using analog tachomter to run with 6143 insted of DSA h/w. but its timebase plot flickers...why?

[QiaoGuo]

Would you please describe where and how the flicker happens? Is it in the plot area or the tree legend on the right side?

I could not reproduce your problem with sound and vibration measurement suite 7.0  and PCI-6143.

It would be nice if you can provide us more configuration information.

Message Edited by QiaoGuo on 09-03-2009 12:45 AM

[m_tahir_m]

Thank you QuaoGuo for your abrupt reponse. i have atached two images for you to understang my problem better. unfortunately these pics are not of my original programe as i am away from my desk but hopefully you can understand well. i used three analog inputs;

channel1- sin wave of suite amplitude

channel2- same sin wave

channel3- another sin wave with phase difference of 90

... all have same frequency less than 40 hz

i see the flickered signal for very short time with almost every loop iterations.

i was using trail version of SVMS 7.0 with labview8.6, same is repeated with SVMS2009 now.

best regards.

[m_tahir_m]

Thank you QuaoGuo for your abrupt reponse. i have atached two images for you to understang my problem better. unfortunately these pics are not of my original programe as i am away from my desk but hopefully you can understand well. i used three analog inputs;

channel1- sin wave of suitable amplitude

channel2- same sin wave

channel3- another sin wave with phase difference of 90

... all have same frequency less than 40 hz

i see the flickered signal for very short time at almost every loop iteration.

i was using trail version of SVMS 7.0 with labview8.6, same is repeated with SVMS2009 now.

best regards.

[preston_johnson]

I believe your code is flickering as you are not providing continuous data.  These functions expect continuous data.  Your read block in the loop is N samples, meaning that you skip some time data in between loops. 

Consider using the DAQmx Express VI to set up a continuous data acquisition stream. 

If you want to perform an N-sample acquisition, you need one that has enough rotations for all the filtering to work.  You will need (or allow for) the filters to reset each iteration.  This reset is most likely the cause of the flickering. 

[m_tahir_m]

thanks.

1- the task is used with option of "continuous data"  not "N samples".

2- however "DAQmx read" function input "samples per channel" is  being  tested with 500-2000 samples.  3- Also the task sampling rate is tested from 1k to 5k with the signal freq of less than 40 hz

regards

[preston_johnson]

your pic code jpg file indicated a N sample acquisition.

can you post the code behind the jpg file?

[m_tahir_m]

Hi Preston Johnson, Please find here the attached vi for your comments about the flickered time base plot discussed earlier. I also tried DAQmx Assistant but got same results, unfortunately. Regards.

PCI 6143

LabVIEW 8.6

Sound and Vibration Measurement Suite 2009

DAQmx 9.0

[QiaoGuo]

I may understand what your flicker problem refers to and I am curious about how you caught the attached pic_flickering.JPG.

Imagin a display plot of current iteration is from 0s-1s, the display plot of next iteration is from 5s-6s, when the timebase plot updates, its X scale's maximun first turns to 6s, then the X scale would be from 0s-6s, but the new data is from 5s-6s, which is located at the right side of the plot; finally, X scale's minimum turns to 5s, then the plot is displayed from its minimum to its maximum.

I guess this is probably the "filcker" which you saw.

But I think it is reasonalbe because if you set a breakpoint after the "stop"control then run the VI, in every iteration stop, the final stablized timebase plot is correct.

[m_tahir_m]

Thanks QiaoQuo,

1- It looks quite logical to me as the data compressed on the right of the plot for a while before the new data ploted, but issue is how can i monitor the plots online as real time data. can you please send me timebase&orbitPlots.vi, already posted ro you, back after emending to work properly.

also note that even if you stop the program and toggle few mouse clicks between view options of plot on the tree legend, i.e. filtered and unfiltered, you can see the same effect of flickering on the plot data already published.

2- another issue i couldn't understand what Preston Johnson pointed to earlier that code like timebase&orbitPlots.vi needs continuous data to operate properly as online/ continuous monitoring. In the program task_3ch used is configured to acquire data continously. no difference is noted even i used DAQmx Assistant inside the loop for continuous data streaming. Yes, i got the point that the block of data provided by the AI Read.vi is limited at every iteration and the progam works as it got N samples instead of continuous data and the loop continue because of the config. of continuous data. and even  if you don't specify  the block of samples using  'no of samples per channel' input of AI Read.vi, it will fech all data available in the buffer and yet the result will be a block of data. in this case your data is just delayed to be define as real time. isn't it?

how can i achive real time data continuously. if there is a way then how the filters in the loop works with- out a suitable set of data. 

kindly send me the code works for online monitoring with config. of 'continous' option.

best regards