Analog Trigger Problem

[Taylor]

I have a VI for acquiring data from multiple devices synchronously using RTSI.  I am attaching a copy of my VI.  It seems that no matter what I set the trigger voltage to, it will not start acquisition until the trigger signal reaches about 250 millivolts.  Has anyone else seen this problem before.  Can anyone help me?

Thanks,
Taylor

[Taylor]

Forgot to mention, the boards are PCI 6110 and they do have the RTSI cable connected.

Thanks

Taylor

[Travis G.]

Hello Taylor,

Have you been able to successfully start acquisition from an analog trigger (at your specified level), on just the master device?  Verify that you can do this first before trying to send that start trigger line over a RTSI line.  Take a look at the Traditional NI-DAQ shipping example (Help >> Find Examples) titled Acquire N Scans Analog Hardware Trig.vi, located in the NI Example Finder under Hardware Input and Output > Traditional DAQ > Analog Input > General.  Verify that this works correctly for you.

Have you ever considered programming with the NI-DAQmx functions?  If your device supports them (which most do), the NI-DAQmx API is much easier to use, and actually operates more efficiently on a driver level than most Traditional NI-DAQ functions.  There is a good NI-DAQmx shipping example titled Multi-Device Synch - Analog Input – Finite Acq – Analog Start.vi, that can be found in the NI Example Finder under Hardware Input and Output > DAQmx > Synchronization > Multi-Device.  This example shows how to do exactly what you are trying to do in NI-DAQmx.  I hope this helps.

Regards,

Travis G.

Applications Engineering

[Taylor]

The Acquire N Scans Analog Hardware Trigger is working properly.  I'll look into the DAQmx stuff and let you know.

Thanks,
Taylor

[Taylor]

Sorry about that.  I went back and looked at the voltages I was reading a little closer.  I connected a voltmeter to the BNC that is going into the DAQ board.  So I opened up the Acquire N Scans Analog Hardware Trigger vi.  Let's say I set the trigger level to 0.01V or 10 mV.  Then I start adjusting the potentiometer on the device that I'm acquiring voltages from.  It waits until it hits about 260 mV to begin acquisition.  Could this be a hardware problem? 

Also, I currently do not have the DAQmx software.  Is it downloadable or how do I go about purchasing it?

Thanks again,

Taylor

[Taylor]

I am currently using LabView 6.0.  If I understand this correctly, DAQmx is not compatible.  Is this correct?

Thanks,

Taylor

[Travis G.]

Hello Taylor,

Yes, you must have LabVIEW 7.0 or later to use the NI-DAQmx API.  You must upgrade your LabVIEW software to take advantage of this driver.  You can download the NI-DAQmx software for free from our website here:

NI-DAQmx Download

I also came across this Knowledgebase, that discusses why sometimes slow moving trigger signals can sometimes be filtered out accidentally.  Take a look at this document, and try the workarounds listed in the solutions portion to see if this solves your problem:

KB 2ZD9B3W3: Analog Trigger Not Working for PFI 0 on a PCI-61xx Device [link removed; article no longer available]

Let me know if this works.  I'd be interested to know if that's the cause of this issue.

Regards,
Travis G.
Applications Engineering