NIFGEN PCI-5421 noise and marker output

[pegli]

Dear all,

I have a PCI-5421 function generator that I am using in the arbitrary sequence mode. However, we see in our system that the NIFGEN produces way more noise when we don't have it in the disabled "quiescent" state. We see a quite increased noise output when we output waveforms that are all zero compared to when we disable the device. This is a problem for us during the segments where the output should be anyways 0. Therefore, I thought to use a fast isolation switch which I enable while the NIFGEN is actually outputting something. During segments with no output, I would open that switch so the noise cannot get in our system. I thought about using the marker output for this. Is there a way to make the markers stay on the "high" level during the full waveform segment? I have seen that you can switch them to the toggle mode. However, this doesn't really work for us as we want to have in on the high state only when the corresponding waveform segment is played. Furthermore, our waveform segments have different length.

Thank you very much for your help!

Peter

PS: We use Labview...

[kirsch]

You could use the LSB in your waveform as a Data Marker Event and route that out however you need.

See:

• NIFGEN_ATTR_DATA_MARKER_EVENT_DATA_BIT_NUMBER
• NIFGEN_ATTR_DATA_MARKER_EVENT_OUTPUT_TERMINAL
• NIFGEN_ATTR_ANALOG_DATA_MASK
• NIFGEN_ATTR_ANALOG_STATIC_VALUE

However, I find your statement:

---

we see in our system that the NIFGEN produces way more noise when we don't have it in the disabled "quiescent" state. We see a quite increased noise output when we output waveforms that are all zero compared to when we disable the device.

highly suprising. The instrument shouldn't be producing more noise when generating a waveform of all zeroes versus being in the idle state, as far as I understand. How are you measuring this noise? Have you reproduced this on multiple instruments?

[pegli]

Thanks for the idea with the LSB. I think I will try this. Currently, I am uploading the waveform using the "niFgen Create Waveform (poly).vi" with the data type Data:WDT wired to it. What would be the cleanest way to add the desired increment on the LSB?

[kirsch]

Create your waveform as an array of i16. You will have to configure Sample Rate separately if you aren't doing so now.
Then use bit operations to make the LSB 0 throughout and 1 whenever you need the marker to be asserted.

Another, perhaps easier option for you, is to use toggle mode like you originally said, but use a script (and script mode) to state exactly in which samples it is that you want the marker to toggle. Are you familiar with script mode and the 5421's scripting language?