data acquisition (save to disk)of 1kHz sine-signal with cRIO9073 and AI (NI9205)

[JanK123]

I am trying to acquire a voltage sine-signal (+/- 10 V) with the Compact Rio Modul (9073).
This signal should be saved in a file.

I managed to do this following the instructions in the "Getting Started with CompactRIO and LabVIEW" document. I followed the "Creating a project in scan interface mode" section.

My problem is, that The sample-rate is way to low. I tried changing the timings in the timed loop but it did not help.

Is there any solution to the problem of data acquisition with my cRIO (using a NI902 Analog Input Module) to acquire and save my signal?

Attached please find my model:


Thanks for your help.

[jkurtw]

JanK123,

The rate of the scan engine is configured from the cRIO controller's property page in the LabVIEW Project.

Right click on the 9073 controller and select Properties... then select the Scan Engine field on the left. Here, you can set the I/O scan rate.

Your timed loop should be set to "Synchronize to Scan Engine."

As you can see from the scan mode benchmarks, depending on how many channels are in your chassis, setting a scan rate of 1kHz consumes quite a bit of the CPU time on a cRIO 9012 controller. The 9205 has 32 channels, which is beyond the number of channels your controller can scan at 1kHz as you can see in the table below.

Number of Channels (AI/AO pair)	100 Hz	500 Hz	1000 Hz
1	10%	32%	55%
16	16%	47%	95%
32	18%	67%	n/a
64	27%	96%	n/a
80	29%	n/a	n/a

Currently, the scan engine only performs single-point I/O, meaning it reads one point at a time so that you can perform an operation on that point before asserting an output, such as PID.

Single-point I/O can be used for slower acquisitions, but once you starting getting close to 1kHz or higher, buffered acquisition is necessary, reading multiple points at once.

Using LabVIEW FPGA, you can use a DMA FIFO to acquire at the full rate of the 9205 (250 kS/sec).

Hope this helps!

Kurt