How to make 9215 and 9211 work together in cRIO9014?

[carsale]

 

I try to make NI Analog input 9215 and NI thermocouple input 9211work together in the same FPGA VI based on cRIO9014 (LabView 8.5). But failed. Fig.1 shows the block diagram of FPGA VI without 9211 when a signal of 50 Hz input (from a function generator); Fig.2 demonstrates the block diagram of FPGA VI with 9211 under the same signal. The retrieval signal is obviously not right. I don’t know what is wrong. Please help me! Thanks in advance!

Carl

[Stephen_Moore]

Hi Carl,
The reason is quite simple, the 9211 has a much slower sample rate, only 70ms per channel (420ms for four channels), compared with the 9215 which can sample at 10 microsecs.
When you have both AI in the same loop then the loop speed will be determined by the slowest AI module.  All you need to do is to separate the AI into two loops, one as per your Figure 1 and a second loop to work with the 9211.  Your Figure 2 output is what you might expect when sampling a 50Hz signal at approx 14Hz which is what you are running at with the 9211.
Hope this helps.
Cheers
Stephen

[carsale]

Dear Stephen

Thanks so much for your help. I have modified the code as shown in Fig3. the situation has improved but it seems there are still some data missing. the loop rate was 1000 Hz and I think it is enough for the 50 Hz sine signal. could you tell me how to fix it, please? I really appreciate your help.

Kind regards

Carl