[cRio-9039] FPGA data logging

[jeongho630]

Hello,

I am trying to log data at the maximum possible sampling rate using a cRIO-9039 with NI-9239 (voltage) and NI-9211 (temperature) modules installed. To achieve high-speed logging, I configured my VI by referring to the method described in the following NI Knowledge Base article:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000x3ruCAA&l=ko-KR

However, I am encountering two issues.

1. The sampling rate of the NI-9239 is significantly lower than expected.
   As far as I understand, the NI-9239 should support up to 25 kHz when using two channels. In my case, however, the data is being logged at only a few hundred samples per second.

2. The actual measurement data is not being logged correctly.
   For the NI-9239, the logged values remain at 0, and for the NI-9211, the logged values remain statically at approximately −2, regardless of the applied input signals.

The version of LabVIEW I am using is LabVIEW 2015.

Thank you very much for your time and support.

[ZYOng · Accepted solution]

1. The sampling rate of the NI-9239 is significantly lower than expected.

You place both NI-9211 and NI-9239 in the same loop. The NI-9211 is slowing down the NI-9239. Use parallel loops so that both can run at their maximum rate. See the example below to log synchronized data via a single DMA FIFO.

Both loops are from shipping example at Help >> Find Examples... >> Hardware Input and Output >> CompactRIO >> Module Specific IO >> Analog Input

2. The actual measurement data is not being logged correctly.

Make sure your signal are connected and grounded correctly. See Troubleshooting Offset, Incorrect, and Noisy Readings of NI Multifunction DAQ

[jeongho630]

Thank you!!