200077

[zhoulmnk]

Hi,

I am using NI_DAQmx tools in matlab to set up my AI channel. When I try to read to AI channel, the baseline of the sine wave shift continuously up and up (I used a function generator to produce the sine wave which the baseline is on zero). I met the similar problem before, when I was using the Data Acquisition ToolBox in matlab. I set the ai.inputtype='SingleEnded' to fix this problem. But right now, I am using the NI_DAQmx tools, how can I set the ground in the right way?

If anybody knows the way to solve this problem, could you please tell me?

Thank you so much! 

liming

[zhoulmnk]

I try to read data to AI channel.

I am not sure how to use DAQmxAIAutoZeroMode. I always got error code 200077.

Here is my code.

[a,b,taskMasterAI]=calllib(

'myni','DAQmxCreateTask','',taskMasterAI)

taskAIChan1='/Dev2/ai0';

[a,b,c,d]=calllib(

-10,10,DAQmx_Val_Volts,

'myni','DAQmxCreateAIVoltageChan',taskMasterAI,taskAIChan1,'',DAQmx_Val_Cfg_Default,'')

nsample=1000;

[a,b]=calllib(

DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,nsample)

'myni','DAQmxCfgSampClkTiming',taskMasterAI,'',1000,

[a]=calllib(

'myni','DAQmxSetAIAutoZeroMode',taskMasterAI,'',

DAQmx_Val_Once)

[a]=calllib(

'myni','DAQmxStartTask',taskMasterAI)'doublePtr',readarray);'int32Ptr',0);'uint32Ptr',[])'myni','DAQmxReadAnalogF64',taskMasterAI,1000,10,DAQmx_Val_GroupByScanNumber,...

readarray_ptr,arraylength,sampread_ptr,empty_ptr)

)

After I execute the DAQmxAIAutoZeroMode, the error -200077 will appear.

I don't know what's wrong with my code.

If someone knows, please let me know.

Thanks!

numofchans=1;

nsample=1000;

readarray=ones(numofchans,nsample);

readarray=double(readarray);

readarray_ptr=libpointer(

sampread_ptr=libpointer(

empty_ptr=libpointer(

arraylength=uint32(numofchans*nsample);

[a,b,c]=calllib(

[enderWiggin10]

The error 200077 is a DAQmx error stating that a requested value is not supported by a property.  Is there any text or explanation that accompanies the error?  It sounds like you are requesting something that is indeed not supported.

What is the NI device you are using?

A good place to look would be the DAQmx C Reference Help.  Search for the DAQmxCreateAIVoltageChan function.  You can then find the property for terminalConfig, and then note that you shouold set this value to DAQmx_Val_RSE instead of using  DAQmx_Val_Cfg_Default as you have specified.

I do not think that the device you are using will have/implement the Autozero function.

Best,

[zhoulmnk]

Hi Adam,

Thank you for your replying.

I am using PCI 6221 right now.

If this device has not the AutoZero function. How could I set the right ground for my analog input channel? I know I can set single ended ground or differential ground in labview. But right now I am using matlb to call DAQmx. I am not sure what I should do.

liming

[Dennis_Knutson]

You should do what Adam told you to do about the channel config. DON'T specify DAQmx_Val_Cfg_Default like you are doing now and specify DAQmx_Val_RSE just like he said.

[zhoulmnk]

Thank for everyone's reply. I got it.