Changing Ni scope V/div results in signal saturation

[gvanhoeke]

Hello everybody !

I am using a NI PXIe-5114 scope card in my PXI system and I am facing a issue ...

In the test panel of that card in NI MAX, according to the V/div settings, the signal is cut-off or not just as if a saturation was applied (even though the amplitude can definitely be displayed on the screen ...). 

The problem is that in my LabVIEW vi's when I call the NI scope, I always get this saturation because I haven't found any option to tune the V/div from a vi ...

Can anyone help me see where I am going wrong with the use of my NI scope ?

Thank you in advance !

[crossrulz]

There isn't really a V/div for the NI scopes.  No screen, so no divisions.  Instead, you have a range, which is the maximum value you can read.  You set this with the Configure Vertical VI.

[gvanhoeke]

I have already tried this block but adapting the range doesn't eliminate the saturation ...

I think the range and the V/div are still two different things and from what I understood, we have access to V/div in NI MAX ... (where the screen is contained in the NI scope test panel).

Attached you will find a video showing my problem.

Many thanks for your help.

[CollindeWit]

Hi!

I am Collin de Wit, an Application Engineer at National instruments. If I understand correctly you are not using any code to retrieve the signal, only using the test panels in MAX correct?

It would be great if you could upload some screenshots with a higher resolution so I can take a look at the settings. What is the behaviour that you would expect? What signal are you providing? Have you tried connecting the signal to other channels and is the same thing happening?

Hope to hear from you.

Best regards,

Collin de Wit

[gvanhoeke]

Hello !

That's it, the screenshots are extracted from the test panels of NI MAX.

I will send higher resolution pictures when I have the opportunity to go back on the system again.

What I expect is seeing a full pulse, not a "cut off" one. I know from another oscilloscope and the instrument from which the pulse comes that the pulse does not end that straightly. The same thing happens on channel 1 & 2.

My current solution is to use a stronger attenuator in the input of my scope channels. (I used 20dB attenuation before, because I send up to 300V pulses and it can hold on with 40V only - the pulse sent in those tests is a 90V one so with 20dB attenuation it results in 9V amplitude received).

Replacing the 20dB attenuators with 30dB attenuators allowed me to use all the "V/Div" available in the test panel of NI MAX without getting my signal in saturation.

Many thanks for your consideration, I come back to you as soon as I have got better screenshots.

Kind regards,

Geoffrey