How to use Data Acquisition Toolbox to record voltage?

Hi, I wish to use the data acquisition toolbox to record a voltage input for an extended period of time (~10 min). For some reason, the data acquisition stops after 1 sec even though I use the wait function. Also when I generate 1V, Matlab only seems to record 0.28V. Why is this?

Here is my code:

ai=analoginput('winsound')

addchannel(ai,1)

start(ai)

wait(ai,600)

stop(ai)

[data,time]=getdata(ai)

plot(time,data)

I appreciate any suggestions anyone has. Thanks!