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Emulating DAQ assistant in traditional DAQ

Hi,

 

I have an old DAQ card (DAQcard AI-16XE-50) and I am trying to get an encoder input into labview 8.6. Encoder output is X4 / quadrature.

I did the DAQ part successfully, using two digital line read functions, but my loop runs at 10ms. So if my shaft rotates too quickly, I loose pulses and  the angle reading is wrong.

 

On the other hand, on DAQmx if I use a simple DAQ assistant no matter how slow I run my loop which asks for the reading from the DAQ assistant, the DAQ assistant output is perfect. I am assuming without me coding it to do so, it continuously tracks the pulses from the encoder and 'knows' the angle value, but I ask it to reveal  it to me  once every 10ms only.

 

Could anyone help me emulate this DAQ assistant performance (behind-the-scenes reading of an encoder independent of loop time) using the traditional DAQ pallete available in labview 8.6 and maybe some nested loops and logic? I tried looking at the guts of the DAQmx thing but I couldn't figure it out.

 

Alternatively, If I have no option but to buy a newer laptop USB DAQ system, please let me know. 

 

Any help is greatly appreciated,

Sincerely,

Hasan P

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There may something you are setting differently between your Daqmx task and the Daq Assistant. The best way to decipher this would be to right click your Daq Assistant and select Generate NI-DAQmx Code. This will convert your assistant exactly as it is to the corresponding DAQmx VIs. Note: the channel and task setup gets placed in a subvi, open this up to see the details and make changes.

 

Regards,

 

Anna K.

National Instruments
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