In Arduino mega 2560, 2 computers have different value

Now, the microcurrent of the plant is measured and received by a computer. If I receive it with an unpowered macbook, the value is low and the values ​​when touched and when not touched are also accurate. On the other hand, when USB is connected to the imac connected to the seuquence power supply, the value is not measured and only the high value is received. Do you know what the problem is?

We have no clue what you are talking about…
Read how to use the forum and post the right information…
(Seems like a grounding issue if you have some capacitive sensor)