Setting of nidaqmx constant, Coupling:AC/DC/GND using nidaqmx Python package

[Swapnil@CEA]

Hello,

I am using PXI 4462. The name of my channel is 'Dev1/ai0'.

I do know by default the following program reads the data with DC coupling(Just for testing, I use the signal generator to give voltage input to channel Dev1/ai0 using different DC offsets). But for my applications I would like to read this data with AC coupling for this channel:Dev1/ai0.

I have gone through the documentation of nidaqmx python package which says about nidaqmx.constants.Coupling such as Coupling.AC=10045;Coupling.DC=10050,Coupling.GND=10066. But apparently I could not succeed in implementing it in my code.

How and where can I say/input this information in my code. 

The code is as follows:

with nidaqmx.Task() as task:

        task.ai_channels.add_ai_voltage_chan('Dev1/ai0') 
        task.timing.cfg_samp_clk_timing(Samples_Per_Sec=50000, source="",                                             active_edge=Edge.RISING,sample_mode=AcquisitionType.FINITE,              

                samps_per_chan=50000)
        data=task.read(samps_per_chan=50000)

Thank You.

[sherlockholm]

Hi Swapnil,

What commands have you tried?

Have you tried something like this?

Task.ai_channel.ai_coupling = nidaqmx.constants.Coupling.AC

[Swapnil@CEA]

Hi Jacob,

Thanks for your inputs.

I did try using AIChannel like,

AIChannel.ai_coupling = nidaqmx.constants.Coupling.AC  (But, it did not work)

The alternative that you have proposed did not work for me(I get an attribute error).

By the way, I believe in your answer you mean to say 'task.ai_channel.ai_coupling' and not 'Task.ai_channel.ai_coupling''.

After going through the documentation of nidaqmx and also the source code I do not see 'ai_channel' attribute in Task (and so the attribute error is justifiable).

Swapnil

[sherlockholm · Accepted solution]

Swapnil,

Sorry I did mean task not Task. I did some more digging and I think this might work:

with nidaqmx.Task() as task:

            chan = task.ai_channels.add_ai_voltage_chan("4462/ai0")

            chan.ai_coupling = constants.Coupling.AC

            data = task.read()

            print(data)

Let me know if this works for you.

Thanks!

[Swapnil@CEA]

Hi Jacob,

The solution suggested by you "chan" works perfectly fine for me.

I think I was making mistake for using the right syntax, to assign properties defined in a specific 'class' in python.

Thanks again for your help.

Swapnil