Measuring the Voltage via Camera

Hello, I am currently working on a drone project. Here is my setup:

  • NavIO 2
  • Power Distribution Board (PDB)
  • Runcam (camera)
  • FPV

I saw a video where you can solder the violett wire of the camera to the red cable (positive contact) of the PDB, where the battery is connected to. Because NavIO requires a power module like here these contacts are used by the power module. The question is where do I solder the cable to display the voltage on my FPV, on the PDB where the power module is connected or to the power module where the battery is connected?