Sorry, AI0+ and AI0- were mistype. AI0 and AI8 are correct numbers.
I could solve the problem of the extremely small signals from an analog input chanels.
We have to turn right the screw of the terminal to clamp the wire, but I turned left to fix it.
When even turning the screw left, the wire can be clamped, but the contact between the wire and the terminal seems to be unsufficient.
The bad contact between the wire and the terminal made signals indeed small.
Thank you for our attention. 😁