Time of Updating data from NI-9217 in High Speed mode

[sdyzyzyz]

Dear Sir or Madam, 

Now I have a cDAQ chassis 9174, on which there are NI-9203, NI-9217, NI-9411, NI-9472 modules. (version 9.2.3 DAQmx Harware diriver installed) I only wired a RTD (Pt3851, 100 ohm) in 4-wire mode to physical ai0 channel of NI-9217. And other modules have empty input. The attachment is a simple vi which tests how long Labview will take to update the data from NI-9217 in High Speed mode and High Resolution mode seperately. 

As a result, the attached vi shows that Labview takes around 450 ms in High Speed mode and around 1050 ms in High Resolution mode. It is far away complied with what is described in the manual (400S/s means 2.5 ms per channel in High Speed mode). 

Since the sampling speed is more important to me, I wonder whether there is any problem with my setting? Or you can help me provide a possible solution to program in Labview, which can satisfy no more than 20 ms per channel in High Speed mode? 

Your quick response is highly appreciated. 

Thanks, 

Desmond Yuan 

Email: desmond.yuan@emerson.com 

[HVAC_master]

Mr. Yuan

I was able to get the sample rate to 5 hz by using the DAQmx timing moduale.  I still have not figured out how to get it into high speed mode.

I set up outside a while loop by creating a task (Create Task DAQmx), seting the timing(stopwatch logo DAQmx), and then starting it (Start DAQmx).   Inside a while loop I had the read DAQmx.  After the while loop I cleared the task.  

Please let me now if you figured out how to get the 9217 into high speed mode.

thx 

Kevin

[sdyzyzyz]

Hi, Kevin 

Thanks for your information. I took a class on the DAQ hardware and it helped a lot. 

It turned out the High Speed mode should be set up through "Property Node" and configued before when programming.

Zhi 

[mishhell]

Hello,

I have the same problem. Can you give me a example, how you solve it, please? 

[Brad_K]

Set the DAQmx Channel >> AI.ADCTimingMode property.

Brad

[mishhell]

Yes, I know this, but 1 sample still takes over 400 ms for 2 channels (without High speed mode 1600 ms). I though, Dzyndys has a better solution.

[Brad_K]

Hi mishhell,

Are you starting the task once per sample? (Or letting it auto-start?) That would significantly increase your sample time. Make sure you're calling DAQmx Start only once, and measure how long it takes to call DAQmx Read. Once the task is started in high-speed mode, each call to DAQmx Read should take about 2.5 ms * number of channels.

If you're already calling DAQmx Start only once, please post a code snippet demonstrating the problem and relevant info about your configuration (OS, DAQmx version, chassis model number).

Brad

[mishhell]

Now is everything OK. Problem was in the combination Timing setting and High speed setting together. Thanks a lot.