NI-Scope Analog Start Trigger possible?

[ChristophHS]

Hi,

We will will be using a 4 ch osciloscope card PXIe-5172 for an application to record an analog waveform between an analog rising and falling edge.

I am trying to understand if I can use NI-SCOPE VIs.

As written here a reference trigger transitions the device to the post reference trigger sample state, aquiring a fixed number of samples.

What I need to set is the start trigger, but this may only be a digital edge.

I'm a bit puzzled, am I missing something? For me the idea of an horizontal window defned by two levels does not appear to be too complex.

What seems to be possile: Hardwar trigger on first level, detect second level on the PC and use a software-trigger. Don't know if it's reliable with high sampling rates.

Could I maybe combine multiple ADC-Channels, one for falling, one for rising edge ?

If I'm correct the only other option is to use the "NI LabVIEW Instrument Design Libraries for Reconfigurable Oscilloscopes" and develop a Host and FPGA application - which I'd want to avoid (looks rather complex).

Regards

Christoph

[Gregory]

Edit: never mind, ignore this post.

Look at the "Analog Window Ref Trigger" detailed here:

http://zone.ni.com/reference/en-XX/help/370592AB-01/scopeviref/niscope_configure_trigger__poly/

[Gregory]

Sorry, I think that is still just a "start acquisition" trigger. 

If you can, I would try to set it up for the worst case scenario (i.e. the most data you expect to need to collect), and collect both your data and analog trigger signal. Then you could trim off the end of your data by searching for the "stop taking data" transition in LabVIEW, as a post processing step.

I think it would not be efficient to tell the scope to keep collecting data until a transition happens, because it must need to set aside the buffer for the data before hand.

[ChristophHS]

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@Gregory wrote:

Sorry, I think that is still just a "start acquisition" trigger. 

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Thanks anyway for the help!

If I'm not mistaking thats a reference trigger, which marks the end of an acquisition + a fixed number of post reference samples.

However the analog window is just another analog trigger type.

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@Gregory wrote:

If you can, I would try to set it up for the worst case scenario (i.e. the most data you expect to need to collect), and collect both your data and analog trigger signal. Then you could trim off the end of your data by searching for the "stop taking data" transition in LabVIEW, as a post processing step.

I think it would not be efficient to tell the scope to keep collecting data until a transition happens, because it must need to set aside the buffer for the data before hand.

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Side Info: The signal itself is contains the trigger (rising/faling edge with threshold).

I'll test using two channels. One triggering on a rising edge, the other one on a falling edge.

When a falling edge is detected (data availabe at host) a softwar trigger may work to stop acquisition.

Don't know if it does work with the PXIe-5172. And even if it does it's not a clean solution but suitable in my case.

I just feel like I'm just not seeing the obviously correct way to do this.

Christoph

[ChristophHS]

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@ChristophHS wrote:

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I'll test using two channels. One triggering on a rising edge, the other one on a falling edge.

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Please ignore this. Correct me if I am wrong, but you can only have a single reference trigger. Which makes sense in context of the scope-applications.

I think what I am trying to achieve is not possible using the digitizer hardware with NI-Scope-Library.

I will try to use a different approach by continuously streaming the scope measurement and process the data on the host (PC).