Pre-trigger data for multiple channelssharath

[sharathnu]

Hello,

I am trying to build a simple programme to acquire analog inputs for multiple channels.  I need to set pre-trigger samples in the programme and it should be triggered by one of the AI signals. The problems are as follows

1. When I use Reference trigger, I get an error saying my device supports reference trigger only for a single channel and all the other channels should be removed.

2. When I use a Start trigger VI followed by "Reference Pre-Trigger" property node, It does not give values in the pre-trigger. I have attached the VI which I have used to create Pre-Trigger samples.

Hardware

NI- PCIE6361

BNC-2110

Can anyone tell me what is the issue in Hardware/ Programme and how I can put pre-trigger samples for multiple analog channels?

[sharathnu]

Edit:

I have attached an image of the block diagram.

[sharathnu]

Edit:

I have attached an image of the block diagram.

[sharathnu]

Edit: Vi block diagram is attached

[Kevin_Price · Accepted solution]

The last part of the error text you posted provides a 2nd alternative -- specify the analog trigger source as a *terminal* rather than a *channel*.   That might look like "/Dev1/APFI0" rather than like "Dev1/ai2".  Then you'd further need to parallel wire the signal both to the channel that acquires it and *also* to the APFI0 pin. 

APFI pins are present on devices that support analog triggering.  My understanding is that such devices have special circuitry dedicated to detecting analog triggering conditions which is *separate* from the main Analog-to-Digital conversion circuitry.  The APFI pins are used to route signals into the trigger circuitry while the regular ai channel pins route to the A/D circuitry.

-Kevin P

[sharathnu]

Thanks for taking the time to reply. It is my fault that I did not write the question in the right manner. The error in the image corresponds to the situation where the Start Trigger is replaced with "Reference Analog Edge".

And,

The block diagram that I have given using the combination of  Start Trigger and Reference Trigger property node does trigger the device. But it does not acquire the pre-trigger sample. There is no issue with the triggering of the channel. The only Concern is that of the absence of the Pre-Trigger Samples.

Clarification: The error occurs when I code using the DAQ Assistant.

When I replace the DAQ assistant with the VI wherein the START analog trigger + Reference Trigger Property Node is involved, the Reference Trigger terminal indicator shows as DEV1/ai

I have attached the front panel of the VI

[Kevin_Price · Accepted solution]

I wasn't fully clear either, but I *was* addressing that original situation where you wanted to configure a "Reference Analog Edge" trigger rather than a Start Trigger.   You'll *need* some version of reference triggering in order to get Pre-Trigger samples.

(The later scenario that uses a Start trigger *can't* give you pre-trigger samples.  Your attempt to define reference trigger properties is apparently being ignored since reference triggering isn't relevant in that scenario.  I'm actually a little surprised it doesn't throw an error or at least a warning.)

So anyway, please try the suggestion in my previous post.  Define a Reference Analog Edge trigger by using the special APFI0 pin.  That should allow you to have a multi-channel task that gets triggered by an analog signal and gives you pre-trigger samples.

-Kevin P

[sharathnu]

Thanks, Kevin. That Helped.

So, AFPI is required to have pre-trigger samples.