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concurrent AI AO cDAQ-9184

Equipment: Labview, cDAQ-9184, AI: 9205; AO:9264; also in rack: 9402

 

Task: AI ->  PID process -> AO, as quickly and smoothly as possible, bandwidth about 10-20Hz is adequate.

 

Problem: executing AI alone using continuous samples, exhibits very fast loop time - around 5mS; executing AO using one sample on demand, exhibits similar loop time. When these tasks are placed in a single block (per NI advice on tightening performance) executing time increases to around 40mS and is too jittery to be acceptable for the application.

 

We are trying to used "single point, hardware timed" mode. We understand that concurrent hardware timed processes are available for cDAQ-9184, we get error 20077 ("feature not available...").

 

Would appreciate help answering two questions:

1. Why does adding the AO after the AI, in a single block, cause a nonlinear increase in processing time? And is there a trick to making this happen?

2. Why is the single point hardware timed mode not available for the 9264 on the cDAQ-9184 when all indications suggest that it should be? And is there a configuration trick to getting this to work?

 

Thanks for suggestions.

 

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Hi julianop,

 

According to this link, cDAQ chassis don't support hardware-timed single point acquisition, therefore, no cDAQ modules will support hardware timed single points acquisitions.

 

Also, I recommend you to put the read and write operations in separate loops.

 

Best,

 

Carmen C.

 

 

 

 

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