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NI 9215 data sampling and acquisition

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Hi,

I would like to explain to you what my system looks like and would appreciate if you could suggest some modifications to speed it up.
I am running my LabView Program on a cRIO 9022. Now this cRIO 9022 is connected to 3 NI 9144 chassis via a daisy chain. Each NI 9144 has a NI 9215 mounted on it and is sampling an ac voltage signal (on one channel only. Rest are open). These signals (from all three modules) are sent over to the NI cRIO 9022 which takes a decision.
Now I want to visualize how fast this process is taking place. The fastest that I am able to see is 1ms on a graph, so i am not able to confirm whether the system is running at a faster speed (given the fact that NI 9215 can sample at 100 ks/s/ch).
Also I think I am confusing data acquisition with data processing. I have set the scan period of my RT controller to 300us. Does that mean my NI 9215 modules are sampling at 3333.33 Hz? If not, can anyone please help me figure out how to change the sampling speed of NI 9215.


 
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If the sample rate of the controller is set to 300 us, that would meean indeed it samples the channels in that speed. The 9215 does not have a free running clock like the delta sigma modules. It samples when the scan is asking it to do so. The ethercat connection is not build for high speed but for synchronization. All of your three modules are sampled at the exact same time with jitter in ns range.

The 300 us are probably the maximum of what you can do on cRIO and you will get an error if you try to further increase the rate.

One option to increase sample speed would be to move to the FPGA of the 9144 chassis. The FPGA could max out the 100 kS rate and you could make your analysis at the fpga and then send your analysis result over to the cRIO chassis for further decision.

PXI instead of cRIO would allow to achieve up to 10 KHz sample rate.

 

DirkW

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Accepted by topic author homer210788

Thank you so much for the explaination.

Now I am running the program on cRIO at 300us scan period. I want to show a pulse on to a oscilloscope whenever the acquired sample exceeds a predefined threshold. I have acheived this by writing a string "111111" on the serial port and connected the write pin to the oscilloscope. But theoritically, it should show it in milli seconds, but it takes around a second to show it. Is it because of some delay on the serial port?

Will a device such as NI 9401 be suitable for such purpose?

 

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