Accuracy/jitter when using software triggering of PXI card I/O

[User002]

If using software timing/triggering for control of PXI I/O cards, is there any data (or at least rule of thumb) for how this affects jitter and cross-channel synchronisation? I expect there isn't a hard number, as the performance will depend on what level of load the CPU is under, but some ballpark figures/worst case may be useful.

I've found a page on the PXI6704 (What is the Maximum Update Rate of my NI 6703/6704? - NI)

which shores up a gap in its datasheet, to explain the delay in updating a signal after a software trigger, but can't find this for some other cards I'm looking at. And this is the delay on top of potential delays/jitter due to the software trigger itself.

I'm interested in similar info for the PXI6512 for output, as well as the effect on monitoring using PXI6511.

[santo_13]

Tighter synchronisation is only possible through hardware triggers. Using software triggers is slightly better than using initiate/fetch/measure commands. Unfortunately, as it is a software-based command, it is completely dependent on the OS to execute it.

A lot of settings and implementation techniques are at play beyond hardware capabilities. Please describe your requirements and application for PXI6512/6511.

[User002]

Thanks for the response.

My outputs' update rate may need to be as fast as 10ms (100Hz). I have not yet determined my monitored inputs' sample rate but may be similar.

From my existing knowledge of triggers, I'm concerned that this might be a bit too much for software triggering, especially over many cards (synchronising them all). To add to the complication, I'm likely to need multiple PXI chassis due to the number of signals - this makes me more nervous about triggering. Perhaps something like a PXI6683H in each chassis to distribute a sync signal, and then choose hw timed cards?

From a cost perspective it would make more sense to sw trigger if achievable.

[santo_13]

Multichassis synchronization is definitely possible using the Timing & Sync cards (not simple though). Now you venture into the domain of feasibility analysis and potentially adding/replacing hardware.

If you have 1095 chassis with the T&S option, then it makes it easy to do multi-chassis synchronization. Please describe your application to guide you better.