Data Rate for Each Channel in Flexlogger

[marx87]

Hi All,

I am using  cDAQ-9174 +  NI 9205  to obtain voltage measurement . Noticed that there are 3 type (slow, medium, high) data rate selection in Flexlogger. Understand that we can configure the 3 type selection with different data rate. But it seems like i can only apply 1 from the 3 selection (either slow, medium ,high) to all my channels. In another word, all my channels have same data rate.

How do we configure each channel with different Data rate. Example AI0 - 1khz, AI1 - 10khz, AI2-5khz...

Please advice. Thank you

[Tommy_G · Accepted solution]

Hello marx87,

At the moment, you are only able to select the data rate in FlexLogger at the module level. For example if you had two C Series modules in your chassis, they could each run at a different rate, but all of the channels within a single module are limited to the rate at the module level.

We are always looking for feedback for the product, so I appreciate you creating a post to let us know your interest in this. Do you mind sharing a little more about your application and your interest in having different channels within a single module run at a different rate? Feel free to post on here or send me an email at Tommy.glicker@ni.com.

Thanks,

Tommy

[Devin_K]

Hi marx87,

Just to expand a bit on what Tommy mentioned above, this is a result of limitations of the cDAQ hardware you are using.  You can only use a single task and rate for all channels in your NI 9205 module, and overall your cDAQ-9174 chassis allows you to use up to 3 different AI timing engines, allowing you to have 3 different AI tasks with different rates (providing you have multiple modules, as Tommy mentioned).  If you attempted to write a LabVIEW application yourself which used different rates on the same module, you would get a resource reservation error.

In order for FlexLogger to support different rates on channels within the same module, we would have to do something like acquire all channels at the fastest rate, then downsample/resample the other channels to slower rates.  This isn't something that FlexLogger currently does out-of-the-box, so feel free to respond with further details or email Tommy so we can keep this sort of functionality in mind as we continue to improve and add features to the product.

[marx87]

Hi Tommy_G,

Firstly appreciate the response. I am actually using the modules to obtain voltages from slip ring system. The system contains several type of signals and i also will be obtaining signal from proximity sensor (impulse on number of turns & speed). Some of the signal especially from the slip ring system require high data rate to form the waveform, compared to the signal from proximity sensor. The impulse signal from proximity sensor doesn't require high data rate. So in my opinion, its not an efficient way of managing the date rate resources.

[marx87]

Hi Devin_K,

Thank for sharing. Appreciate it. 

Actually I am new to Flex logger & cDAQ. I have used Labview and USB 6211 module before. We can actually set different date rate for each channel in the system. Based on your explanation, this limitation on data rates in due to the cDAQ modules. Thank you