acquire multiple channels with scxi 1520

[didje]

I would like to acquire multiple channels from a Scxi chassis in multiplexed mode.
One of the module is a 1520 which I'm using for load measurement.
I would like to use all the functions in the example on a per channel basis.

My question is how can I select the channel for Filter settings, Strain Null and Shunt Cal as I need my driver to be totally configurable as the user needs to select these options at run time.

[Ian Colman]

Hi,

The example that you have provided shows how to set up a channel’s Filter settings, Strain Null and Shunt Calibration by changing controls on the Front Panel of the VI. Would it be possible for you to give a little more information on your desired application as I am unsure as to what you need to do that isn't covered by the 1520 example. If you would like me explain how the example works in more detail then that’s okay, but I suspect you need additional functionality so wanted to check specifically what additional functionality you require.

Best Regards,

Ian C.
Applications Engineer
National Instruments UK & Ireland

[didje]

Ian

First thank you for looking at my query.

The example does everything I need for one channel, I want to do teh same thing for 4 channels and also acquire some 20 other channels from the SCXI.

The main thing is that I want to be able to set each load channel in a totally different way as the other.
The channel propery node from DAQmx is wired to the task (which in this case contains only one channel). In my application the task will contain more than 20 channels and only four of them are load channels (the other are current loops)and may be only one of them will need a filter to be applied.

I should have asked how to select the physical channel to which the DAQmx Channel property node refers to?

Thanks

Etienne

[Ian Colman]

Hi didje,

I've written this VI for you that should demonstrate how to do what you require. Note that the custom control "state control.ctl" is required by "Configure Multiple Tasks.vi" to run.

The VI is based using the state machine architecture. If you are unfamiliar with the state machine I suggest you turn on "execution highlighting" by clicking the light bulb icon in the block diagram and watch the programs execution. If you have any questions don't hesitate to ask.

Best Regards,

Ian
Applications Engineer
National Instruments

[didje]

Hello Ian and thank you for your reply

You seem to assume that  after creating a virtual channel the Channel Property node will automatically refer tot his channel.
If you could confirm that it will always be the case then it would simplify my programming as I was planning to use the Task property to extract the channels in the task and then use the Channel property node to set the properties required.

I am going to set up a sysem with  my 30 and test the system

thanks

Etienne

[Ian Colman]

Hi Etienne,

What we actually do here is create a Task that contains several channels. You can configure many chanels in a single task using property nodes. You specify which channel a given property node adresses using the "ActiveChans" input of the property node. Hope this helps, let me know.

Ian

[didje]

I understand what you mean.
In the example you posted, the active channel is not selected for each channel property node.
Does DAQmx select by defualt the last channel configured?

Thanks

Etienne

[Ian Colman]

Hi Etienne,

The active channel is selected in each propery node using the 'ActiveChanns' Input of the property node. The attached picture should show how the task name is entered on the Front Panel at 'A', assigned to the task at 'B', then used to specify the channel properties at the property node at 'C'. Hope this helps.

Ian

[didje]

Thank you