internal clock as gate signal

[you.did]

Hi Sean,

I could not open your attachement because "LV version (7.1) is newer than version (7.0)"!?!

But I tried it with my first example again. I found out that it works if I use (Reserved_2) as Gate Signal. I don't know what is the timebase of this signal, probably 100Hz. But maybe you can tell me how to find a proper solution with this example.

And it turned out that I have another problem: I want to two measurements to be synchronised and started at the same time. So I will need a start trigger signal, too. I tried to choose the same RTSI-line in the DAQ-Device to synchronise it with the position measurement, but it did not work.

I will attache my VI, I hope you will help me.

Thanks a lot,
Judith

[Sean_C.]

Hi Judith,

I have attached that VI is saved as a LV 7.0 VI. You should be able to open it now.

I tried to open your VI, but I am missing the "Counter Start Trigger (NI-TIO).vi." Where did you find this VI?

Also, I notice that you are using a DAQ Assistant in the same VI as the Traditional DAQ Counter VIs. Are you trying to communicate with the same board with the DAQ Assistant and the Traditional VIs? If so, you will generate an error. You can only use one driver to access the board at any given time. I recommend using NI-DAQmx (on which the DAQ Assistant is built) to build this VI. DAQmx is much easier and much more intuitive than the Traditional DAQ Counter VIs. Once you get the attached VI working, it is easy to synchronize 2 measurements. Simply set both of your DAQmx Timing VIs to the same clock source (in this case the internal output of a counter).

To make sure that both measurements start at the same time, use a DAQmx Start Trigger.vi. Then set both measurements to use the same start trigger.

Please let me know if you have any trouble getting this VI to work. Also let me know if you have any further synchronization questions.

Regards,
Sean C.

[you.did]

Hi Sean,

the DAQmx sample works now with the counter clock, tank you! In the other example, the DAQ assistant measured a voltage with an different device so there was no error.

I tried do this measurement with the counter clock using a LabView-example (see attachement). An error said: "No registered trigger lines could be found between the devices in the route." How can I do a measurement with device2 when the counter belongs to device1?

Thanks,
Judith

[you.did]

... and I want to start both measurements if the voltage exeeds a certain limit. I tried it with the attached VI, but I don't know how to set the trigger source.

(By the way: how can I edit a post in this forum?)

Thanks,
Judith

[Sean_C.]

Hi Judith,

You can only edit a post within 5 minutes of posting it...

In order to use a counter signal from one DAQ board as a clock on a different board, you will have to provide some path for that signal. The easiest way would be with a RTSI cable. Then you would not get that error. Alternatively, you could externally wire the counter output from one board to a PFI line on the second board and use that PFI Line as the clock source.

To trigger off an AI channel, simply wire that physical channel name to the "source" teminal on the DAQmx Trigger.vi. See the attached VI.

I hope this helps.

Regards,
Sean C.

Message Edited by Sean C. on 06-02-2005 05:43 PM

[you.did]

Hi Sean,

the synchronisation of the measurements works now, thanks a lot.

But still I don't know how to start both measurements at the same time. I can start the voltage measurement (Device1) with the analoge start trigger, but not the counter-measurement(Device2). In the example of the triggered counter measurement you can only choose a digital edge. I tried the DAQmx start trigger VI but it did not work. Can you help me out?

Judith

[Sean_C.]

Hi Judith,

Do you have a RTSI Cable installed? If so, you can just trigger the counter measurement with the Dev1/ai/StartTrigger. When the analog task receives its analog trigger, an internal StartTrigger is generated. You can trigger the counter measurement with this.

If you do not have a RTSI Cable installed, you will have to use the DAQmx Export Signals.vi to export the Start Trigger from Dev1 to a PFI line. Then externally wire Dev1's PFI Line to a PFI Line on Dev2. You could then trigger the counter measurement off of the Dev2 PFI Line.

I hope this helps. Please let me know if you have any further questions.

Regards,
Sean C.

[you.did]

Hi Sean,

no I have no RTSI Cable installed (because I had no idea how to do that) I conected two PFI lines externaly.

I could not route the start trigger signal to an PFI line ("Specified route cannot be satisfied, because the hardware does not support it.")
If I chose PFI0 it sais "...because it requires resources that are currently in use by another route" Obviously the analog start trigger uses this PFI line somehow.

Judith

[LYu]

Hi Judith,

I took your program previously posted and added a route VI and was able to route the Start Trigger to a PFI line. Please make sure the PFI line you're routing to belongs to the corresponding device (e.g. if start trigger is from Dev1, route to Dev1 PFI line). You can then use external wiring it to route this trigger signal to your second device.

P.S. I took the DAQ Assistant out from the code because it was causing problem on my computer. You can use the attached code as an example.

Thanks,
Lesley

[you.did]

Hi Lesley,

I could not open your VI because I only have LV7.0

Thanks,
Judith