Hi Jing -
Since you said you're building your scheme based off of an example, I'm going to assume you've already included a Save Data or Save Data with Trigger block in your DAC scheme. This is mandatory if you want to use Data Storage with either of the two following techniques.
If you're running your DAC scheme programmatically, are you using the SchemeMeasTest() command, or the SchemeMeasStart() command? If you want your DAC scheme to be run with Data Storage (Data Portal or File) enabled, you'll need to use the SchemeMeasStart() command. The other command merely runs the scheme with visualization only (as a test).
If you're running your DAC scheme interactively, are you pressing the Start Display button or the Start Measurement button (see below)? These two buttons are the interactive versions of the aforementioned programmatic commands. If you want to test your visualization without Data Storage, use the Start Display button. If you want data to be saved to either the Data Portal or File, use the Start Measurement button.
Let me know if this still doesn't help.
Dear Derrick :
Thank you so much. I'll test very soon. But I'm sure your solution really works since I remembered that I click Display botton, not the Measurment one. Thank you.