Missing Data When Using cDAQ-9174 and cDAQ 9189

[evangelineems]

  In the acquisition system, there are two cDAQ-9174 chassis each installed with three NI 9203 modules, and one cDAQ 9189 chassis equipped with eight NI 9203 modules. I am using 98 of these channels for continuous current sampling at a frequency of 100Hz, with 100 samples returned each time, and the return type is analog 1D waveform (N channels, N samples).

  In this state, data is often missing. After changing the return type to return continuous intervals every 0.1 seconds, the data is still missing. I have tried methods such as powering the acquisition equipment separately and powering the USB interface separately, but the result has not improved.

  What could be the reason for Data Missing?

[santo_13]

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@evangelineems wrote:

  In the acquisition system, there are two cDAQ-9174 chassis each installed with three NI 9203 modules, and one cDAQ 9189 chassis equipped with eight NI 9203 modules. I am using 98 of these channels for continuous current sampling at a frequency of 100Hz, with 100 samples returned each time, and the return type is analog 1D waveform (N channels, N samples).

  In this state, data is often missing. After changing the return type to return continuous intervals every 0.1 seconds, the data is still missing. I have tried methods such as powering the acquisition equipment separately and powering the USB interface separately, but the result has not improved.

  What could be the reason for Data Missing?

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This should be a software problem, please share your code to see if there is a bug.

[clarab]

Hello,

One possible issue is that if the software doesn't read fast enough, hardaware of buffers can overflow, causing data loss. 

Please let me know if you need any further assistance or additional clarification. 

Best regards,
Clara 

[evangelineems · Accepted solution]

Thank you for your reply! The question has been solved. The data missing occurs because the negative terminal of the data acquisition card's power supply is connected to the product ground. When the product's relay switches, the instantaneous large current may cause problems with the acquisition function of the data acquisition card with a certain probability.