Signal problem while finite triggering and continuous triggering

[alexlelion]

Hello,

I am currently struggling with my program. It is about: triggering the AWG with a created burst which sends it to a piezoelectric after beeing amplified. A laser (digitizer) is here to measure the signal after and show it on the Front panel.

I want to send a burst (finite trigger) but it doesn't work, although if I choose the continuous triggering, it works. I can't figure out why.

I have done many different attempts of program, and i am attaching two VIs on this message, so that you can maybe help me. The older version (08.01.16) is a version that worked one afternoon. After saving the program, i shut down the computer. The next day, I open it, and it doesn't work anymore. I have explained everything in the VI.

The second one from 11.01.16  is a program that I think should work and I don't understand either why it doesn't.

Could you help me?

Thanks in advance

Alexlelion

[JosD]

Hi Alexlelion,

I will look into this. Can you give me some more information so I can understand better what the problem is?

1. I am missing sinburst.vi, might be trivial but can you attach it?

2. Which AWG and Digitizer extaclty do you have? And which controller and chassis, and maybe other HW? 

Now the more important questions:

3. You send a signal from the AWG to a Piezo electric element via an amplifier. Then the laser should measuren, but a laser is not a sensor. What do you exactly measure and how? Also. what do you ahve wired to what?

4. If I understand it correctly, you want to send a burst of triggers to the Piezo to excite it, and then make sure the measurement (as described under 3.) with the Digitizer is taking place synchronized. Is that right? Or do you mean to do something else? And do you intend to repeat the burst + measurement?

5. You say 'doesn't work.' What do you mean by this? Is the code not runnable,  do you get run-time errors from LabVIEW or is the generation or reading of the signals not taking place as they should (while no errors are reported)? IN case you get run-time errors, please attach a printscreen or description.

With kind regards,
Jos Deurloo

[alexlelion]

Hello and thanks for your concern 🙂

1. I am attaching the sinburstVI to this message

2. AWG = NI PXI-5412 (14bits 100MS/s) , Digitizer =NI PXIe-5122 (14bits 100MS/s)

3. I didn't precise it in the first message indeed : I am using a laser-vibrometer, so I can indeed use it as a sensor here

So the laser is wired to the vibrometer and the vibrometer is wired to the digitizer

4. I just want to send one trigger (sinburst) everytime that I click on the button "send trigger", so just a windowed sinus with a number (i take 5 usually) as number of sinus. I send this signal to amplifier and then to excite the piezo (on the surface of the material), which sends a wave and I want to catch the signal received by the laser on the surface of the material further with the laser-vibrometer, and show it. I would repeat the burst+measurement indeed, to have different signals since in the future I 'll want to save up those data.

5. Doesn't work as in ´. the program runs, but no signal is shown by the digitizer, and i also noticed that instead of sending only one burst, the trigger doesn't stop once I stop clicking the button- (i used a 10kHz frequency to hear it, and it only stops when I stop the program entirely, which is not what I aspire to)

I have done many versions of it, but I don't know what the problem really is, if my program is wrong in the base or it is just a few details.. 

And also, everytime I get to have something interesting and I save it, the morning after, some parameters (of the express VIs I use) changed somehow and it doesn't work anymore for some reasons. Like now for example, I got on tuesday afternoon some kind of progress (just managed to show the laser signal, but very low and undesired continuous trigger), I saved the program. Today I wanted to continue to work on it, and something is now wrong with the express VI Ni-fgen sample number. I really don't understand it.

Thank you again

[JosD]

Hi Alex,

In test laser 11.01.2016.vi, you are using code to synchronize multiple AWG cards with TClk. Is that intentionally done? Or do you intend to sync the AWG with the Scope?

Based on you answer I will set up a small example VI for you and a quick test here to see how your requirements can be met.

Best,

Jos

[JosD]

Hi Alex,

Please find attached an example, where the AWG is triggered by the user, and as soon as it starts, it sends out a HW trigger to a PXI line. That is picked up by the scope to measure an X number of samples. You need to play around with the sample speeds and number of samples, and make sure that the AWG produces the signal you need (right now I just let it generate a sine). The Reference Position setting of the Scope trigger enables to acquire pre trigger samples.

If a start trigger is not enough and your measurements require synchronization based on sample clock, you can export the sample clock from the AWG (just change the enum usin in step 7a) and for the scope use code similar to the LabVIEW example niScope EX External Clocking.vi.

Let me know if this helps!

Kind regards,

Jos

[alexlelion]

Thanks a lot for your help, I will take a look on your suggestion.

I will tell you if it helps or not, but it should 🙂

Best regards

[JosD]

Hi Alex,

Any findings?