Problem triggering NI-9234 from 9401

Question

I am trying to trigger a 9234 from a 9401 connected to a PLC. There are 4 input triggers connected to the first 4 channels of the 9401, corresponding to 4 phases of a test. For each phase of the test, I am looking for a trigger on a different channel. The problem is that the acquisition is triggered from any of the 4 input channels, i.e. when I specify a trigger on the first channel, PFI0, a trigger from PFI1, PFI2 or PFI3 also causes the acquisition to launch.
In using the NI example, “Acq&Graph Voltage-Int Clk-Dig Start.vi”, I am able to reproduce this behavior. I configure the trigger source to be PFI0, Rising Edge, on the 9401. The acquisition is triggered even if the rising edge is passed on channel 1, 2 or 3. Trigger signal level is 0-5V.
LV2011, DaqMX V9.4, Windows XP
Attachments:
Acq&Graph Voltage-Int Clk-Dig Start.vi ‏28 KB

Answer 1

I have figured out the problem and the solution. To simulate the triggers sent by the PLC, a box was made containing 4 switches supplied by a common 5V source. Apparently, electronic noise is generated when a switch is activated and fed back though the other switches. This was causing erroneous triggers to be detected. So, I added a trigger property node, enabled the digital filter on the trigger signal with a minimum pulse width of 0.1 milliseconds (0.0001 sec). This cured the problem of triggering from any channel.
The filtering will also be useful to help eliminate false triggers caused by electronic noise in the production environment, which has also been a problem.
Thanks for all those who viewed and I hope this can be helpful to someone in the future.
Joe
Attachments:
Acq&Graph Voltage-Int Clk-Dig Start Dig Filter.vi ‏30 KB