Guys, I'm back, I self-calibrated DHO914S and tested the noise floor, which is probably between 210uVpp~260uVpp, which is basically normal. I tested the BODE plot and found a bug that when the CH1 or CH2 channel gear is much smaller than the signal amplitude of the AFG, it runs without any display, which is unacceptable, and I guess it is not able to automatically adjust the vertical gear of the oscilloscope to adapt to the signal source. I didn't know if it was just me who appeared, and then I connected my homemade 16-channel LA and the test results were satisfactory. By the way, I got another 250M bandwidth for free, and now the only thing missing is VESA100 Didn't arrive, I'll make up later, thanks.