PCSGU250 wave sequence from library

Instruments PC Generators
#1

Hi everybody,
I am using a PC generator PCSGU250 to generate some signals.
The goal is to generate a burst every 100ms during 2 second ( so 50 bursts) and then a pause during several second. And to repeat this signal.

I have write a lib file called onde.lib and i use it with the sequence genrator :
4 20 0 1 2.27 onde.lib

The lib file is a kind of ( 0,0,0,0,0,0,0,1,-1,0,0,0,0 )
The thing i don’t understand is : what correspond to frequency for this kind of library signal in the wave sequence.

For example if i set 20Hz in frequency field, does that mean that the entire library file will be read in 50ms, or each sample of the file is read in 50ms, or other ?

If someone have some technical information about this, i am very interested !!!

Thanks

Cedric

#2

The library file represents one cycle of the waveform.
The whole file is output at the selected frequency.

#3

Hi,
Thank you for your answer, this help a lot.

The thing is i look at the signal generated, and now i set a frequency of 20Hz during 1 second. So i should have 20 time my file, and i have it 21 times !!

This is not a big issue because if i reduce the time to 0.95 second, it seems that i have 20 time my signal.

The mean problem is that between the reading of two file, or at the end of the reading of the file, there is some artefact signals that appears. and this signal is bigger than the usefull signal …

Any idea ?

Thank you in advance.

Regards

#4

Please see this thread for a solution: viewtopic.php?f=10&t=12794

Here’s the link to download the updated PCSGU250 software: app.box.com/s/5t5hoclqyay8i3gsswqk

#5

Hi,
Thank you again. This improve, but i still have some strange artefacts.

Now i have some big DC signal 100ms long. This occur at the end or beginning of each lib file.

I don’t know how to post an image, if you need to see the signal generated don’t hesitate.

May i have a driver problem ?

Thanks
Cedric

#6

[quote]I don’t know how to post an image[/quote]You can upload the picture to a free file hosting service and post the link here.

Do you get any problems if you use e.g. the library file burst01.lib with the settings used in this example?:

burst111.png800×478

If your output voltage is low, there may exist some DC offset.
You can improve the result by adding some opposite offset as done in this case:

burst210.png799×477

Can you please post the content of your library file?

#7

Hi,
Yes, I have the same result than you, with burst01.lib, and I can observe the same problem if i put the voltage output at 0.2V

So i tried to reduce the DC offset with opposite offset, but it is still " noisy".

So the solution i can use, is to set a High voltage output, and then attenuate the signal outside the PCSGU250.

Does an improvement of the DC offset is possible in the future ?

Here is my wave form :

0,00 (253)
0,9
0,5
0
-0,5
-0,9
0,00 (254 )

Regards

Cedric

#8

[quote]So the solution i can use, is to set a High voltage output, and then attenuate the signal outside the PCSGU250.[/quote]Indeed, this is good solution.

[quote]Does an improvement of the DC offset is possible in the future ?[/quote]The digital-to-analog converter for the DC offset is 8-bits. So the DC offset resolution is 10V/255 = 39mV.
At the moment no plans to make modification.