Oscilloscope connection NI PXIe-4300

[wenxiuluo]

I am a beginner of a Ni device and I would like to ask why the waveform on the oscilloscope is like this when I connect the probe of the oscilloscope to the Al +of the COM1 of the NI PXIe-4300? I'm sure my grounding terminal is intact.I hope someone will answer for me, and I will be very grateful to you.The connection mode and waveform diagram are attached.

[santo_13]

The image you posted was captured using an external oscilloscope or using the 4300 AI?

Question - what do you use to generate the signal and how is it connected to the 4300 AI and the oscilloscope probe?

[wenxiuluo]

The NI 4300 is housed in the NI 1082 case, as shown in figure, and the image I released is using an external oscilloscope.I connected the Al + of one of the 4300 channels to the oscilloscope probe with a dupont cable, and the Al- connected to the oscilloscope's ground terminal.

[Vazgen_H]

Hello, wenxiuluo.

For the first try to check all wires. 

Check input impedance to be the same as the source (50 Om or 1MOm)
Check AC, DC coupling.