sensor 0v

how do i know where to which sen0v pin(a,b,c) on motec m150 connected to which av or dig pin or all sen0v are just connected internally

You need to configure your firmware package. You need to use the matching 5V/0V pairs for any AV power. When you configure the resource, it will ask with Voltage Reference (A/B/C) is being used. For AT inputs, you need to use 0V A for AT 1 and AT 2, use 0V B for AT 3 and AT 3, and 0V C for AT 5 and AT 6. This is all in the help for any of the "Voltage Reference.

When I do M150 wiring looms, I will balance the AV's across two of the 5v/0v combinations (typically A and B) and then have all of the switching, frequency (flex fuel sensors) and rotational (Crank, Cam/s and Wheel speeds) sensors on 5v/0v C. The AT's are allocated based on their internal pull-up configurations.