max record NI-5124

[Sastry]

Hello,
The first question I would like to ask you is, are you using the Modulation Toolkit to perform the demodulation? The Modulation Toolkit vis are continuable in nature that is they are capable of processing data as it comes in. This is achieved by maintaining the state information. You will notice that most vis have a "reset" boolean control input to them. Setting this control to "false" ensures that it has the state information which is used by new data coming in.

So I would recommend that just like you have been acquiring data in chunks to avoid the memory issues, please read the file in chunks and perform the demodulation on these chunks and make sur eyou set the "reset" control to false.

Please do let me know if you have any questions.

Regards,
Sastry

[Naturalarch]

Hello to you to,

for starters, thanks, this is welkom information and yes i am using the demod toolkit. So i will first try to make some nice program and try to demod the PSK data stream.
If i don't succeed i will contact you. and if you like it i will post the program when it is finnished (or at least doing something).

Best regards

Joost

[Naturalarch]

I got an other question for the same system....

I am now saving a signal in the following order:

input in the 5600 Downconverter, translate the 406.028MHz to 6.028 MHz. Then it goes into the oscilloscope 5124, where i save it to file after getting a trigger (saving a pulse of 0.52 seconds in a time frame of 0.6 seconds). The format i save it to is *.HWS with data type I16.

Now i want to recollect the correct power levels as it went into the 5600, how can i get these? Because no i don't have any info at what levels the Y axes are when the data is saved...

Best regards

Joost

[DFGray]

If I read your question correctly, you would like to rescale the I16 data from the HWS file.  To do this, you need to save the gain and offset in the HWS file.  There are inputs for this on the Store Analog I16 VI and corresponding outputs on the Retrieve Analog I16.  They are not required and default to gain=1, offset=0.  The wfm info output of the Fetch Binary I16 VI has this information.  This should fix your future problems.  It won't help already saved data.  These numbers should not change much from run to run (provided your 5124 gain is the same), so you can get a very good approximation of the correct numbers by running the system and recording what gain and offset result, then using it for your new values.  You can set scaling coefficients on an existing file, using these new numbers, but using the niHWS Set Scaling Coefficients VI.

Let me know if this answers your question.

[Naturalarch]

Thanks for the reaction. I think this answers how to translate the scope information. But How about the power translation from the downconverter (5600) before the scope (5124).

I added the 2 vi's in wich i think i need to change something...

thanks already..

[chericks1]

Hi Joost,

I believe you will want to use niTuner Get Attenuation.vi to see how the power level changes between the signal inputted to the 5600 and the signal outputted to the 5124.

The attenuation returned is equal to 20log10(scale factor).

The scale factor should be applied to correct the time data returned by NI-SCOPE. The scale factor is equal to the PXI-5600 input signal amplitude divided by the PXI-5600 output signal amplitude.

Please post again if you have further questions!

Chad AE
Applications Engineer