Hi Jingli
(Just a minor addendum)
Yes, You are right, both methods work. In case you need a high data throughput, the default clock method is limited to the operating systems capabilities (so called software timing, appr 2 - 4 kS/s), whereas some DAQ-Hardware also supports hardware timing, which can get You a lot farther (10, 20 100 kS/s), albeit with drawbacks on data visualization.
nimic