How can I capture a hardware trigger (5.76 V, 25ns wide) and use that to trigger something else in LabView

[TSr314]

Hi there,

I am trying to synchronize data acquisition between two different instruments using LabView.

One instrument will be operating independently (it can't be integrated with LabVIew for a number of reasons), and the timing signal from that instrument which I want to use (5.76 V square pulse, 25 ns wide, occurs aperiodically) is 'extracted' (I made a breakout box and have the timing signal on a coax which I can plug into anything).

I want to take that timing signal and use it to trigger some event in LabView (the second instrument is controlled with LabView). 

I had hoped that a USB 6501 would be able to do the trick, but I realize now that it can't see a signal which is so short (I think).

So what should I do? How can I make LabView 'see' such a narrow pulse and use that to trigger some event?

In summary:

• Have digital signal coming from a piece of hardware on a coax - 5.76 V rectangular pulse, 25ns wide, occurs randomly nut not more often than every ms
• Want to input that digital signal into my PC and LabView where I will use that signal to trigger an event (in this case, start a data acquisition event on a different piece of hardware which is controlled with LabView)
• I am using LabView 2013 64 bit, Windows 7x64
• I was hoping to use NI-USB 6501 but I'm not sure it is possible since pulse is so narrow
• A photo of the timing signal as seen on a scope is attached (note there is a tiny bit of ringing which won't be present when I fix the cable)

Thanks,

Sabrina

[TSr314]

One option is to stretch the pulse to make the width a bit more reasonable. If I manage to stretch it to 100ns wide, which digital i/o devices can I use which will see it?

[K C · Accepted solution]

Hi,

You could use a Flip-flop to catch signal. Not catching the pulse but the rising edge. You can read the steady output of the Flip-flop with any DAQ (digital or analog)  device and use the same DAQ device to reset the Flip-flop.

Kees

[TSr314]

That's a great idea! I would have implemented this soulution if I was still stuck with the short pulse.

In the end, for some reason, updating the firmware of the device from which I was getting the timing signal made the signal much wider - it is now 1.5 us long, which is think the USB 6501 shou,d be able to see, since it operates at 5 MHz.

Thanks again for the great idea though! I will have to remember that one in the future.