Collect multiple types of signals in multiple cDAQ chassis

[henry_2020]

Hello everyone

I use 8 cDAQ-9189 chassis to collect vibration, current, and digital signals, and 3 types of signals may be collected on each chassis.

DAQ Start in For Loop

First, I create a DAQ task for the same task type on each chassis, the number of tasks is 13, (Acceleration 5, Current Input 3, Digital Input 5). Then put “DAQ Start” in the for loop to start the acquisition task. Finally, read the data according to the task type.

Each execution of The “DAQ Start” will take about 1s, and all tasks will take 11.7s. Then, when reading the data, the “AvailableSamplesPerChan” property in some tasks will always be zero, and there is no error in this task.

Why the “AvailableSamplesPerChan” is zero but no error is prompted?

DAQ Start Parallel

Second，the “DAQ Starta” and “DAQ Read” of each task are paralleled. The maximum DAQ Start time can reach 20s. But the data reading is normal after starting the collection.

What caused the “DAQ Start” to take too long?

Finally, how to achieve a quick start in such a situation?

Thanks

Henry

DAQ Start in For Loop

DAQ Start Parallel

[henry_2020]

LabVIEW 2015 DAQmx 18.6

[Kevin_Price]

With only partial screenshots, and global tasks defined in MAX or your project, and my limited cDAQ experience, I can't give you a definitive answer.  Here are some things to look into:

- there's a limited # of "timing engines" available on any given cDAQ chassis, some dependency on I/O type

- the concept of "channel expansion", allowing you to share limited timing resources across more tasks

- you're ignoring errors until the very end of the app.  You'd probably get some useful info by paying closer attention to them earlier

-Kevin P

[henry_2020]

I add “DAQmx Start Trigger (Time) .vi” before “DAQ Start”, the input para "When" is set to current time plus 30 seconds. 

At the beginning, the collection was fine, but after a few minutes, the digital input was no longer collected, and no error is prompted.

Is the collection affected by the network status? As there are multiple switches in the entire system.

Thanks

Henry

[henry_2020]

Hi, Kevin

Thank you.

"The cDAQ-9185 chassis has three AI timing engines, which means that three analog input tasks can be running at a time on a chassis. " There are only up to two analog inputs in my case.