06-20-2019 02:48 PM
I can't figure out or locate any documentation to explain how the ADCs work. (I find the info pretty much instantly for competitive products. NI is the exception.)
I need to sample 5 channels, 4-20mA current loops with 16bits\10k samples/second. I'm sampling raw data to test how a communication system will work, so I need to be sure that triggering is operating from the same oscillator. I can't have clock drift between channels. Sampling could be simultaneous (better), or in sequence just so long as there isn't any clock drift between the channels.
My company already has a cDAQ-9171, and I'm thinking that a NI-9203 will do the job, but I can't tell. Another engineer here likes the NI-9227, but I'd need 2 cards, and I'd need to know that both cards sampled simultaneously. I can't tell how this is done.
Does anyone at National Instruments know how these products work? Is there documentation somewhere? (I have the spec sheets... I need actual documentation.)
06-21-2019 08:35 AM
In the spec sheets for both of the cards mentioned, it lists the ADC type, for the 9203 it is a SAR and for the 9227 it is a Delta Sigma. For your use case, I would recommend using the 9203 since the 9227 might be overkill especially since the number of required inputs would force to use two cards. As far as channel drift is concerned, that should not be an issue if you reference all the channels to the same task and clock source within LabVIEW (or whatever you are using).
06-21-2019 10:33 AM
"should not be an issue" is not a clear enough answer. Is there someone who knows about this product available?
06-24-2019 12:36 PM
I should have phrased that better in my previous answer. You can avoid channel drift by synchronizing the channels on the same clock on the device. If you would like to discuss the options more, I recommend you give our Technical Support Team a call at 866-275-6964 and someone would be happy to discuss the issue in further detail to make sure you get a device which fits your needs.
06-24-2019 01:04 PM
Thank you. That is the answer I needed to see.