virtual oscilloscope + trigger ???

[aqw]

Hi, I've got a problem, I have to do virtual oscilloscope wiht NI USB 6008 card, a did everythin but I have only one problem, I cannot do trriger to my oscilloscope, I would like to have a choose rising or down trigger, I take my signal from generator.  Can somebody help me ??

[Matyas]

Hello Aqw!

With USB-6008 you have the option to use digital trigger on PFI 0 line. When an AI task is defined, you can configure PFI 0 as a digital trigger input. When the digital trigger is enabled, the AI task waits for a rising or falling edge on PFI 0 before starting the acquisition. To use ai/Start Trigger with a digital source, specify PFI 0 as the source and select rising or falling edge.

You can use for example an external button as the source of your digital trigger.

Does it answer your question?

Read more in USB 6008/6009 user manual:

http://www.ni.com/pdf/manuals/371303l.pdf

Regards,

Matyas

[Matyas · Accepted solution]

...

Useful starting point:

LabVIEW or CVI >> Help >> Find Examples... and search for "triggering"

Continuous analog acquisition with digital start is what your looking for, aren't you?

Best,

Matyas

[aqw]

Hi, i can't solve this problem, do i have to use digital trigger on PFI 0 ??? i have got analog input signal and i would like to choose rising ot fallinf trigger, so can i do it ??

[Matyas]

Hi,

Please, film me up which method you think of!

1. You have two signals, one to measure (analog) and another one to trigger your measurement (fast analog or TTL digital). Connect your 'signal to measure' to an AI channel, than connect your switching signal to PFI0 >> This is Digital trigger available with USB-6008/9
2. You only have one signal to measure and you want to trigger the measurement with a specific threshold, window..etc. (i.e. start measuring when reaching 3.28 V upwards) >> This is the Analog trigger NOT available with USB-6008/9

Check this KB for some details:

http://digital.ni.com/public.nsf/allkb/7094D0AE57C62A4D86256D7B006AF6B2?OpenDocument

So, if you want to trigger your measurement: use the 1. method and try to connect a simple button with TTL logic to PFI0. OR if it's not okay for you and you need the 2. option...

Theoretically, there's no  problem with connecting a fast analog signal to digital trigger source, because voltage is either way analog.

Please, try it! 🙂 Connect your analog signal to both an AI channel and PFI0 to trigger your measurement with the signal itself!

BUT, beware that the analog signal must be between 0-5 V and should be really fast-rising and/or fast-falling like a square wave signal for full success! We need to protect your equipment...

I hope it helps! 🙂

Matyas

[aqw]

I'll try today and we'll see

[Stefo]

Hi aqw 🙂

As is said in USB 6008 Use r Guide ans Specification, on page 19 in section Digital Trigger:

"When an AI task is defined, you can configure PFI 0 as a digital trigger input. When the digital trigger is enabled, the AI task waits for a rising or falling edge on PFI 0 before starting the acquisition. To use ai/Start Trigger with a digital source, specify PFI 0 as the source and select rising or falling edge."

By other words, yes, you need to use trigger on PFI0.

If you are looking for the way how to implement this solution into LabVIEW, I recommend to have a look at examples (Hardware input and output -> DAQmx -> Analog Measurements -> Voltage -> Acq & Graph Voltage-Int CLK - Dig Start). There should be complete examples for what you are looking for.

Best ergards,

Stefo