How to acquire AI without buffer error

[CLJ]

Hi guys

 I have at problem with my application. I am using 3 cDAQ chassis with a lot of different modules – Both AI, AO, DI and DO. Its for a test stand. LabVIEW is going to control the test stand and log numeric data to an excel file. I am having trouble with the AI readings. One of these three things is happening:1. I get a buffer overflow error (200279).2. I get an error that tells me that I am trying to read a value that is not yet available (200279).3. I get the numeric value several seconds late (Big delay). I have done a lot of reading in help files and on this forum. Haven’t been able to solve this problem on my own. I have made at property node that shows me how many available samples there are in the buffer. I can give in values in the “cDAQmx assistant” that I am using so the number of values in the buffer pretty much stays at zero – This solves some of the problem, but I still get problem nr. 3 at some point of time.   After some reading I have acknowleged that the “cDAQmx assistant” is not suitable for this kind of application. Therefore I have tried to use some more basic cDAQmx VI´s. But I am having difficulties getting these to work with more the one physical channel. What I need is:- To bee able to read live (Not delayed) numeric data from the AI modules (NI 9219 and NI 9215).- To bee able to change the update time from the front panel while running.- To bee able to read from 3 cDAQ chassis with 4*9217 and 1*9215 simultaneously. I guess that should bee it. I have put in a small example of the issue. The example is taken from my application VI.  Hope that you guys can help me! Best regards Christian Jensen.

[andre.buurman@carya]

Would be nice if there was actually code to debug .

Could convert the daq-assistant express vi to code and post a screenshot of the resulting code?

[CLJ]

Hi guys.

I have at problem with my application.

I am using 3 cDAQ chassis with a lot of different modules – Both AI, AO, DI and DO. Its for a test stand. LabVIEW is going to control the test stand and log numeric data to an excel file.

I am having trouble with the AI readings. One of these three things is happening:

1. I get a buffer overflow error (200279).

2. I get an error that tells me that I am trying to read a value that is not yet available (200279).

3. I get the numeric value several seconds late (Big delay).

I have done a lot of reading in help files and on this forum. Haven’t been able to solve this problem on my own.

I have made at property node that shows me how many available samples there are in the buffer. I can give in values in the “cDAQmx assistant” that I am using so the number of values in the buffer pretty much stays at zero – This solves some of the problem, but I still get problem nr. 3 at some point of time.

After some reading I have acknowleged that the “cDAQmx assistant” is not suitable for this kind of application. Therefore I have tried to use some more basic cDAQmx VI´s. But I am having difficulties getting these to work with more then one physical channel.

What I need is:

- To bee able to read live (Not delayed) numeric data from the AI modules (NI 9219 and NI 9215).

- To bee able to change the update time from the front panel while running.

- To bee able to read from 3 cDAQ chassis with 4*9217 and 1*9215 simultaneously.

I guess that should bee it.

I have put in a small example of the issue. The example is taken from my application VI. Now I have also included some screenshots of the VI.

Hope that you guys can help me!

Best regards Christian Jensen.

[andre.buurman@carya]

Could you try this example: \examples\DAQmx\Analog In\Measure Voltage.llb\Acq&Graph Voltage-Int Clk-SW Trig Restarts.vi?

 Replace the IO selection ring with a string control and input "Dev1/ai0,Dev1/ai" where "Dev1" should be replace by your device name.

[CLJ]

Hi André.

Thanks for your reply.

I have done some experiments with the example VI. I do have some problems.

- Cant get it to sample faster then about 1hz.

- Had to change from "commit" to "Verify" in order to get it to work at all.

- Am not sure what you mean with "Replace the IO selection ring with a string control" but I have instead tried to du at timed boolan.

- How to use more then one AI with this sort of acquisition.

Best regards

Christian.