Analog out vs arbitrary waveform genereator

[ErnstPontus]

Hi,

Looking at creating some perodic analog signals with a bandwidth of ~200 kHz in a PXI system.

Can an Analog Output module (PXIe 6738) be used as a 16 channel arbitrary waveform generator ?

Regards,

Pontus Eriksson

[crossrulz]

The problem with the analog outputs is that the bandwidth is shared between channels.  The spec reads 350 kS/sec/ch.  So that 350kHz actually goes to 21.875kHz for each channel.  You might be able to get the bandwidth you want with 4 cards and you only use 1 channel per bank (again, read the spec).

[ErnstPontus]

Thanks for the reply,

I would agree with your comment if the spec said 350 kS/s and that would translate into 10.9 kHz per channel (should be 32 channels and not 16). But the spec states "350 kS/s/ch update rate on 32 channels or 1 MS/s/ch update rate on 8 channels (1 channel per bank)." So the 350 kS/s seems not to be shared between channels or am I wrong?

Regards

Pontus

[JakeA]

Hello Pontus,

The 6738 has one DAC for every four AO channels, and to my knowledge the way that the setup works is that if you're using only one channel per bank it will be capable of 1 MS/s, but if you're using more than one channel the best rate that can be guaranteed is 350 KS/s. I suspect that because of this you would be able to meet your desired spec if you only used eight channels, but not 16. Does this help clarify the way the device works? 

At the bottom of the first page of the device manual it mentions this and links to the pinout so you can have a visual representation of  the setup:

http://www.ni.com/pdf/manuals/375391a.pdf

Regards,

[Clark.qin]

Dear sir,

I've encountered this problem too.

My question is :

If I want to generate 32 sine waves with different phases but same frequency.

Can I do that using one PXIe-6738 at the sampling rate of 350 kS/s per channel?

The 6738 spec says that one bank consists 4 channels using only one DAC.

Does this mean that 6738 has only 8 DACs?

I remember that 6723 has 32 DACs.

What's the working mechanism inside the bank? 

I can accept the simultaneous update within the bank but need different data on each channel.

Can this happen?

Thanks if you can help me.