Changeing "DAQmx_AI_Excit_Src" in python lib

[fmesnnhsr]

Hello Community,

I am currently writing a python program with the NI-DAQmx Python Lib (v. 0.9.0)  using a "cDAQ-9178" with a "NI 9216". I wan to read out the temperature, but I can't get the "ExcitationSource" in the code set. With the NI-Max it is working.

I am running Win10 with a python 3.12.2 .venv. I got the following Error:

nidaqmx.errors.DaqError: Requested value is not a supported value for this property. The property value may be invalid because it conflicts 
with another property.
Property: DAQmx_AI_Excit_Src
Requested Value: DAQmx_Val_External
Possible Values: DAQmx_Val_Internal

Device: cDAQ1Mod1

Task Name: _unnamedTask<0>

Status Code: -200077

When I try to change from External to Internal, following the Doc. The Code looks like this, but I can not enter the "AIChannel" inside the Lib:

import nidaqmx

pp = pprint.PrettyPrinter(indent=4)
with nidaqmx.Task() as task:
    task.ai_channels.add_ai_rtd_chan("cDAQ1Mod1/ai0")
    task.channels.AIChannel(ai_excit_src=10200)
    print("1 Channel 1 Sample Read: ")
    data = task.read()
    pp.pprint(data)

With this I got this error:

AttributeError: module 'nidaqmx.task' has no attribute 'channels'. Did you mean: 'Channel'?

nidaqmx.task.channels.AIChannel(ai_excit_src=10200)

this produces the same error.

cheers,
fme

[santo_13 · Accepted solution]

Try this, not sure where you got the value 10200 though.

import nidaqmx

pp = pprint.PrettyPrinter(indent=4)
with nidaqmx.Task() as task:
    task.ai_channels.add_ai_rtd_chan("cDAQ1Mod1/ai0", ai_excit_src=10200)
    print("1 Channel 1 Sample Read: ")
    data = task.read()
    pp.pprint(data)

[fmesnnhsr]

thanks for the reply Santhosh.

not sure where you got the value 10200 though.

---

I got it from here, it is the value behind the enum. But the hint was correct, I changed the code to following:

import nidaqmx
from nidaqmx.constants import ExcitationSource, ResistanceConfiguration,RTDType

pp = pprint.PrettyPrinter(indent=4)

with nidaqmx.Task() as task:
    task.ai_channels.add_ai_rtd_chan("cDAQ1Mod1/ai0", 
                                     current_excit_source=ExcitationSource.INTERNAL, 
                                     current_excit_val=0.001,
                                     rtd_type=RTDType.PT_3750,
                                     resistance_config=ResistanceConfiguration.FOUR_WIRE)
    print("1 Channel 1 Sample Read: ")
    data = task.read()
    pp.pprint(data)

Thanks!