Reading one channel one sample

Hey Everyone,

I am hoping someone could help me out here. I have a simple application that requires to read one analog sample from one channel on each encoder pulse. i am using a third party DAQ card (DT9804 from Data translation). 

I have attached a screenshot of my VI. Sorry, the VI is little messy.

I use encoder as an external clock and then read analog sample based on that. Since I want to read only one sample on each pulse, I connected "1" to samples per channel on the timing VI. I am writing the data into waveform chart. But the problem I am having is that it updates too slow. It starts updating right away, but finishes the graph updated few seconds after I have stopped turning the encoder. 

Is there anything I am doing wrong. Let me know if there are any questions. 

Any help would be appreciated.

Thanks

manny