05-21-2024 10:38 AM - edited 05-21-2024 10:42 AM
Hi,
so I would like to synchronize multiple NI-9181 chassis modules to be able to acquire analog data. I've read about channel expansion and also tried it, but it doesn't work, even though (quote) "All Analog Input CompactDAQ modules and most Analog Output and Digital I/O CompactDAQ modules are capable of combining channels into a single DAQmx task". Also here is not really specified that you can't use certain chassis, even though they reccomend a few. I've come to the conclusion that it is probably not supported. Honestly it's all a bit confusing for me though. Well, anyway, I've also tried to create n different tasks based on the count of attached devices and setting the same timing and tried choosing one device to act as the master and using DAQmxCfgDigEdgeStartTrig passing "/cDAQ9181-XXXX/ai/StartTrigger" and DAQmxSetSamplClkTimebaseSrc with the value Get-ed from the master to all the other tasks but without luck (says property is not there, even though it shows up in NI max in the routes tab).
We can't really use other chassis types becouse we need the form factor to be that one, but synchronizing them is proving to be quite the hassle. Is there another way to do it or maybe some other functions that I need to use or something else that could work?
I've also thought of using a single task for acquiring the data and on the event fire a trigger to all other devices, but I'm not sure if that'll work and how much latency will I get by doing so, nor if it's feasible for that matter.
Open to suggestions!
05-21-2024 07:28 PM
Unfortunately, cDAQ-9181 does not come with any chassis connector that can be used to route the trigger signal. Depending on the module installed, you might be able to route the timing signal. However, most analog modules do not come with a PFI port and unfortunately, there is no way to synchronize the modules across multiple cDAQ-9181. Your option would be getting a multi-slot chassis.
06-12-2024 04:11 AM
Uhm, we are using 9209 modules, and in the routing tab on NI-MAX they look like they do have timing signals, though maybe they do not expose them?
Sadly we cannot use a multi slot chassis for, as i said before, we need the compact form factor for space reasons... Another idea i had was to maybe start each one separately and then aggregate the results, but that sounds quite the hassle to be honest, and also very imprecise (I'm fine with a few ms drift between each other, but I'm not sure whether that will ultimately cause them to strive too much away from each other).