DASYLab Performance Issue

[Chuck]

I have DasyLab running a simple input to output loop to verify performance.  The input is fed by a signal generator and the output is monitored for replication of the input signal.   I am feeding a sine wave input.   I cannot replicate the sine wave above 100 Hz regardless of using NI PXI hardware or NI CDAQ hardware.   The signal starts chopping at 100 Hz and will completely drop out at 1kHz.   In between 100 and 1kHz the signal just continues to be chopped (stair stepped).   I have tried various configurations of the hardware settings but nothing improves the signal output.    Square wave inputs are even worse.   

[DAQman]

Hello,

Close DASYLab and open NI's Measurement & Automation Explorer (MAX). Modify the analog input task to run continuous and change the sample rate to 10,000 S/s. Run the task to make sure it meets your requirements. Save the task, close MAX start DASYLab. Place a DAQmx Analog Input on the DASYLab worksheet and link to the task. Connect it to a y/t chart for display and run. This should provide much better performance. If you need to modify the sample rate, there's no need to run MAX again because this is one of the few items DASYLab can control with NI hardware.  You may need to set the sample rate higher if you wish to reproduce waveforms above 100 Hz. A good looking sine wave consists of 100 data points. So 10,000 S/s divided by 100 Hz is 100. If you can set the sample rate to 100k Hz, then sine waves up to 1000 Hz should look good.

Best regards,

John

 

[DAQman]

I should also add that if you have control over the block size, set it to at least 10% of the sample rate for acceptable results. A block size of one adds too much overhead and is usually is for sample rates under 100. 

John