Huinan Liang,
Hopefully someone in the community has more experience with this. I can provide you with some links to information regarding the lock-in amplifier startup kit.
For basic information on lock-in and National Instrument's free download follow this link:
"Lock-In Techniques".
You can download and play around with the Lock-In Amplifier Kit here:
"NI Lock-In Amplifier Start-Up Kit".
Keep in mind that the free startup kit has only been tested with LabVIEW 6.1 and that you need one of NI's DSA boards. You can find these boards here:
/sine.ni.com/apps/we/nioc.vp?cid=3472〈=US>"NI-PCI 4451 +4452, NI-PCI 4472"If you still can't find the answers to your questions please post back! Good Luck!
Craig H.
National Instruments