Add a simple delay to the aqcuired signal (won't work)

[jndrk]

Hello there, 

hope you can help, i think it's not that difficult but i don't get it. 

In my USRP Tx i just want to add a variable delay time to my acquired signal for processing. As you can see in the attached picture of my Tx, i get the time information and will add any delay you enter. For example: I want to delay the acquired signal for 50ms. But if i compare the original signal with the delayed signal there is no difference doesn't matter what i entered in the delay-element. I know there's a express VI for time delay, i only used it to see what i should expect, but it's not a durable solution for me. So it won't work and i don't know why. 

Please ask if something is not clear. 🙂 Thank you! 

cheers, 

Jendrik 

[LeopoldK-B]

Hello Jendrik,

i tested you code and it worked fine on my side.

I believe that you just do not see the difference because you did not activate it on your Waveformgraph.

There is a Checkbox on the in the Properties of the Waveformgraph-->Scales which says:

Ignore waveform time stamp on x-axes

if you want to see you you delay in that waverform you have to uncheck that.

Basically you can also convert the express Vi, by right-clicking it and and click on open Frontpanel. Than you can see what happens inside.

Best regards.

L.

[jndrk]

Hi Leopold, 

thanks for your reply. 

I tested your solution, but if I uncheck the ignore time stamp I get something you see in the attached picture. later i formatted the x-axis manually and then i get nothing to see. There's also another problem: Normally if you multiply a sine wave with it's delayed replika you will get a new wave with the doubled frequency and an offset. But in my case i get no offset, only a sine wave with it's doubled frequency. Isn't that a proof that this is not only a display problem?

Best regards,

Jendrik 

[jndrk]

I just wanted to edit my recent post, but i think it's not possible so here's an update: 

Now i understood what happened with my x-axis. I think Labview is converting the time stamp to a double value or something like that. I see my "delayed" signal but only if the x axis is on autoscale. My signal is between 357656114.25 to 357656114.26, haha.

But with this scale a real comparison is not possible. Do you have an idea what I could do that my signal is also between 0 and 0.01?

[LeopoldK-B]

Hi Jndrk,

here is described where the numbers you see come from. It is the Timestamp used by Labview or in your case from the USRP.

http://www.ni.com/tutorial/7900/en/

You could easily set that timestamp to zero with a constant or you subtract the t0 by itself. Then you have your data starting at zero.

Best

L.