Dear Chunzeng, I have the same problem about connecting like Ki-Rak. below is my Instrument and connect: My microscopy is Nanoscope IIIa (mutillmode) SAM (DI). lock-in Amplifier: SR830 (If you need manual I can sent to you) adder (home made) sample: HOPG connecting by myself (refer to above your conversation) : Connect adder (bias output from SAM&