NI-9262 cDAQ buffer limitations, too slow?

[tareyes]

From my understanding of the NI-9262 datasheet, it can achieve 8191 samples through the FIFO buffer before overflow, regardless of the 1MS/s rate that the device is capable of.

For my application, I need to output 25k samples across 9 channels (so multiple devices) at 20kHz simultaneously. Is this somehow achievable with the buffer limitations on the NI-9262?

From the looks of it, NI does not offer any sort of analog output device that is capable of this task. 

[ZYOng]

Are you using Analog Output Regeneration?

Which cDAQ are you using and how often do you want to update your data?

An Ethernet or USB cDAQ will perform differently. See Figure 1 of Instrument Bus Performance – Making Sense of Competing Bus Technologies for Instrument Control

[tareyes]

The samples will only need to be output once, the purpose being to emulate the same waveform that sensors would produce (for example an accelerometer) in voltage. So, I don't believe output regeneration will be needed, as the output only needs to be produced once (per every time the "run" command is ran through a LabVIEW application)

Edit: 9 channels will be used for the purpose of emulating 9 sensors simultaneously.

Would be using either the cDAQ-9178, or 9174 which both interface through USB. 

[ZYOng]

I think USB cDAQ is not capable of doing hardware-timed non-regeneration waveform streaming.

NI cDAQ-9174 Specifications states that it only supports 127 samples per slot for non-regeneration FIFO.

For NI-9262, each channel only gets 20 samples. To output at 20kHz, you need to write the data at minimum 1kHz to prevent buffer underflow. USB communication typically takes 10 to 100 ms hence cDAQ-917x cannot keep up with the streaming speed.

I would recommend replacing cDAQ with a cRIO-9053. It has a slightly larger FIFO for AO streaming (253 samples per slot), which effectively only needs to write the data at 500Hz. As cRIO has its own controller, it can run DAQmx API at 5kHz, which is enough to even output the waveform at 200kHz.

Of course, if you use FPGA mode, you can even output at the maximum rate of 1MS/s/ch.

[tareyes]

Thank you for your suggestion, I will have to look further into the cRIO device and see if it will work for my application. The device will have to be easy to interface with any system, as it won't stay connected to the same computer once deployed. Which is why the cDAQ was the original choice, as the USB communication port was going to be plug and play.