Simultaneous AI AO on PXI 4461

[Kasik]

Hi,

I know this topic appeared many times, but it seems I am still doing something wrong. I use PXI 4461 and try to simultaneously generate waveform and perform signal acquisition. I tried to follow the example Multi-Function-Synch AI-AO.vi, but I receive an error that the task is reserved. I have run out of ideas how to fix it..

I will appreciate any help.

[Zody]

Hi Kasik,

What version of DAQmx driver are you using?

There is a known issue with 8.5 version, try to install the latest one.

The KB you can see below:

http://digital.ni.com/public.nsf/allkb/8C7A7AF1A6DDD00086257399005B8513?OpenDocument

Kind regards,

Ion R.

[Kasik]

Hi!
Thank you for the answer. I use DAQmx 9.5.
Now I receive error

Error -89126. Trigger line requested could not be reserved because it is already in use.

Thank you in advance for any hint..

[Zody]

Hi Kasik,

I believe at the following link you can find an example that should solve the problem

https://decibel.ni.com/content/docs/DOC-11432

Kind regards,

Ion R.

[Kasik]

I tried it also.. But hmm maybe that's a stupid question, if I want to do the synchronization within one board, within PXI 4461, does it need to be on slot 2 of the chassis? If yes, then when I try to change its position to slot 2 it's not seen by the system. What am I doing wrong now?

[ValkoA]

Dear Kasik,

   the particular slot the device is placed in is only important when there are multiple cards to syncronize in the same chassis. Regarding the error code you get, please check if there are any trigger lines reserved in MAX. You can do this in Devices and Interfaces > Triggers. Please refer to the following article for further info:

http://digital.ni.com/public.nsf/allkb/C3BA0E573766745086257A100034F053?OpenDocument

If the problem persists or you have other questions, please get back to me.

Kind regards:

Andrew Valko

National Instruments

[ValkoA]

Apparently the link I submitted does not work anymore, so let me just copy it in here instead:

Problem 

I’m trying to communicate with a module in my PXI chassis with LabVIEW, but I receive the following error.

I’ve tried restarting the device through MAX and have ensured that my LabVIEW coding includes a VI to clear the reference to the instrument yet this error still persists. How can I resolve this issue?

Solution 

In Measurement and Automation Explorer (MAX) you have the ability to reserve triggers on a device. Therefore if a trigger is reserved through MAX, when a VI tries to use the trigger line it will receive an error to say that the trigger line is in use.
To resolve this issue, open the MAX software through Start >> All Programs >> National Instruments >> Measurement and Automation Explorer.
Then expand Devices and Interfaces, click on your PXI chassis and select the Triggers tab at the bottom of the screen. The checkboxes on the Triggers tab denote whether a trigger on the backplane has already been reserved e.g. for third party modules. Ensure that the checkbox corresponding to your device is unchecked and re-run the LabVIEW VI.

Andrew Valko

National Instruments

[Kasik]

Works! Thank you!

[Kasik]

I have one more question. I know that in order to remove the delay I should substract the number of points depending on my update rate. I'm not sure if I understand that clearly, so sorry for the stupid question. I use the property AI.FitlerDelay to get the number of points to discard - is that all? Or the number of points should be the sum of the delay in analog input and analog output? Or something else?

Thank you in advance.

[ValkoA]

Hi Kasik!

 It's great to hear that your application works! The delay that you need to account for is dependent on your purpose with the measurement. If you, say, want to measure a response of a system, then you want the sum of output and input delays (as a sample will be propagated through the system to return back to the input, delayed by both). If you want to monitor the current system state (that is, pair up the output and input values that are observable by the system at the same time) then you'll need to subtract the output delay from the input delay. It is also a good idea to measure delay times before use, to account for possible incorrections. you can find some relevant discussion here:

http://forums.ni.com/t5/Dynamic-Signal-Acquisition/How-to-calculate-ADC-filter-delay-for-USB-4431/m-...

I hope this helps.

Kind regards:

Andrew Valko