Hi everyone,
I have a NI cDAQ 9178 and a thermocouple acquisition card NI-9211. I just want to acquire temperature measurements at 2 Hz. However, when I create a task with DAQ assistant asking for one sample on demand (in a while loop running at 2 Hz) I have a very slow response from the module. The acquisition occurs no faster than 1,5 – 2 seconds. If I test the single channels in NI MAX everything is working just fine.
I am aware this thermocouple module is a “slow one”, but according to the specs it has a max sample rate of 14 samples per second, which is far more than one sample every 2 Hz. Indeed, if I change the acquisition mode and run the loop every 2 seconds asking for 10 samples, the card works. It just has problems with “one sample on demand” acquisition. I also tried with a CDAQ 9174 (4 slots available instead of 8).
I also experienced this problem initially with a 16-thermocouple DAQ card NI-9213. However, in this case it is possible to select a “high speed” acquisition mode rather than a “high resolution” mode when you create a task with daq assistant. With this option all the problems disappear. Unfortunately, it seems that the NI-9211 card does not have this option.
The most surprising and annoying things above all is that if I plug the NI-9211 card into a usb-9162 slot (single slot just powered by USB) and I run the same loop at 2 Hz, the module is working just fine!
Because of this, I would actually assume that there is some problem between the cDAQ 9178 and the 9211.
If I look here, there should be no compatibility issue.
http://www.ni.com/product-documentation/8136/en/
but the truth is, that any while loop with a task from 9211 module runs no faster than 1,5-2 sec if the card is configured with “one sample on demand” mode and is connected to a multiple slot carrier instead of a single dedicated one.
Has anyone ever experienced this as well?
And do you know if there is any solution?
I have LabVIEW 2010.