External Triggering Tektronix TDS320 oscilloscope

[Tallo]

We have a lab view program that controls an electron gun (Kimball Physics) placed in a vacuum chamber and reads voltage on oscilloscope channel 1  without trigger. Now we want to record voltage based on trigger. The scenario is that Electron gun strikes the dielectric sample with stream of electrons as we sweep from electron energy level of 10 eV to 1000 eV in different number of steps and voltage is supposed to be read at oscilloscope channel 1. We have an external pulse generator that sends same duration pulse (Through Channel A and Channel B) to the electron gun (for pulsing electron gun on and off) and to the oscilloscope respectively so that both are synchronized, and voltage should be read at the oscilloscope only when the external pulse is ON i.e. oscilloscope gets triggered. The Pulse ON duration is going to be 200  microsecond and pulse OFF is 1 second. We keep the time delay between electron energy steps as 1 second so that beam energy changes are also synchronized with oscilloscope trigger. 

I want to ask whether it's possible to external trigger oscilloscope for such short time as 200 microsecond and measuring voltage on channel 1 at same trigger ON time of 200 microsecond? Please guide. Thank you,

[Jjohnn]

The first step is to get familiar with the scope trigger subsystem.  If you only want to trigger on a particular input, set the scope to "normal" trigger, select the input trigger channel, and set the trigger level to about half the signal amplitude for a start.

[JÞB]

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@Tallo wrote:

I want to ask whether it's possible to external trigger oscilloscope for such short time as 200 microsecond and measuring voltage on channel 1 at same trigger ON time of 200 microsecond? Please guide. Thank you,

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Of course it Is!  A trigger simply triggers storing samples to a record buffer.  That could include pretrigger samples and you actually might want a few of those since the first moments of the beam can be very interesting.

Anyway,  the record length is simply going to be number of samples / sample rate.  Most Oscopes have a 1,2,5 time base ratio so 20ųsec/division at 10 divisions gets that 200ųsec long record..  but 10% pre samples would cut you short so sacrifice a little time resolution and set 10-20% Pre samples at 50ųsec / division and you can trim off any extra data post capture.  Although again, any resonance at the beam cutout is informative too so, you might want to keep it around. 

You'll probably also want to monitor your vacuum pump current.  Especially at the higher energy levels.   Depending on the target it may outgas faster than the pump can clear the ions and add a vacuum density component to your data that you forgot to compensate for.  Electrons don't fly as straight or fast when H+ and He+ ions go zinging by in clouds and obviously some of your dielectric target will go POOF too.

Do you get the idea that your playing in my wheelhouse?  FUN stuff! 

[Tallo]

Thank you for your message, I got it!

[Tallo]

Thank you for your detailed response, I appreciate it! 

I have worked on the code and it seems to be working. I just have one doubt that whether I am capturing the data exactly at that 200 usec pulse ON duration. Would you like to check my code?

Secondly, could you please tell me that can we measure all points on the voltage pulse being received at oscilloscope. Does oscilloscope has any such functionality or can we somehow use Lab View to measure voltage on all points of the pulse. I have also attached an image of what I am trying to say . As you can see dotted points on the voltage pulse and I want to measure all those dotted points on the voltage pulse.

[santo_13]

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@Tallo wrote:

Thank you for your detailed response, I appreciate it! 

I have worked on the code and it seems to be working. I just have one doubt that whether I am capturing the data exactly at that 200 usec pulse ON duration. Would you like to check my code?

Secondly, could you please tell me that can we measure all points on the voltage pulse being received at oscilloscope. Does oscilloscope has any such functionality or can we somehow use Lab View to measure voltage on all points of the pulse. I have also attached an image of what I am trying to say . As you can see dotted points on the voltage pulse and I want to measure all those dotted points on the voltage pulse.

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About the oscilloscope, the best method is to refer to the oscilloscope manual or reach out to the manufacturer's technical support to get the answer.

About the LabVIEW part, LabVIEW is a programming language like C, C++, it does exactly what you program it to do. In your scenario, if your oscilloscope sends some data, LabVIEW can read it and present it to you for further processing but it does not have a single clue about what that data represents. If your scope does not send the required data, LabVIEW cannot create that data for you unless you have programmed how to create that non-existent data.

[RTSLVU]

In general you need to learn how to use this scope manually as setting a trigger to catch a 200uS pulse is basic scope operation.

When you can reliably catch your pulse manually, then you are ready to begin programming.

Most modern scopes have a LabVIEW driver available in the Instrument Driver Network and come with examples that will make sense once you know how to operate the scope