DAQmx pretrigger on chan ai0 is not possible when measuring multiple channels (error -200264).

[albertz]

I have to sample multiple analog channels (ai0:7) and want to pretrigger (with analog reference trigger) on chan ai0. But I get error -200264. It says: ref trigger is allowed only with one analog channel.
What I am doing wrong? In the old days of traditional DAQ this was possible with so called "conditional retreiving". Is there something equivalent in DAQmx?

I use DAQmx, PCI6071E, and LabVIEW.

Albert Zeitlmeir, MAN Augsburg

[Sebastian N]

Dear Albert,

It is possible to trigger with ai0 and to measure ai0:7.
Use the following example "Cont Acq&Graph Voltage-Int Clk-Analog Start.vi"for a little test.
You will find it in this default folder.
C:\Programme\National Instruments\LabVIEW 7.1\examples\DAQmx\Analog In\Measure Voltage.llb\Cont Acq&Graph Voltage-Int Clk-Analog Start.vi
Some changes you must made:
1. Create a Task in MAX with all AI you need.
2. Use a Task (create channel.vi)
3. Change PFI0 to DevX/ai0

This should be work fine. Hope this helps,

best regards.

SebastianN

[Jeremy_C]

As the error indicates, you cannot have multiple channels in your scan list if you are using one of those channels as a reference trigger. However, you have two options. 1) As the error states, you can change your trigger source from one of your input channels to a terminal (or PFI line). If you are using an E Series, you can wire your trigger signal to PFI0 and use that as your analog trigger source. If you are using an M Series, you can wire your trigger signal to APFI0 and use that as your analog trigger source. 2) You can use the DAQmx equivalent of conditional retrieval. Keep in mind, this is software analysis, so it will not be as fast as hardware, but it is available. Take a look at the example that ships with LabVIEW called Cont Acq&Graph Voltage-Analog SW Trigger.vi. I hope this information helps.