I am building a test probe PCB to test 75-115V. What is the minimum distance between traces that I should adhere to when building my PCB? I will have ground, 3v and 115V traces running next to each other, there will be low amperage, (1ma max), and the board is single sided.
Is it AC or DC that will be running on the trace? If DC then don't worry because that low of voltage won't arc. If it's AC then try to run AC perpendicular to the DC (opposite sides of the board would be ideal) so your collecting as little EMF as possible. Otherwise if your going to run parallel you'll need to do math to find the radius of the magnetic field produced by the AC lines and that would be your gap.
Obviously there are different standards for different environments and applications, so please don't take this as any sort of universal wisdom. But for the UL and CE clearance specs I work with, PCB trace clearance should be at least .2 mils per volt. So if you have 115V difference between two conductors, clearance should be at least 23 mils. Unless your board needs to be ridiculously small for some reason, you shouldn't have a problem quadrupling that.
If it still worries you, the PCB itself is an excellent insulator. Put the high voltage trace on the opposite side from the low voltage.
Remember, batteries can supply enough current to blow traces and components off your board, arc, and potentially explode the battery itself. If you're hooking stuff up to a battery, fuse the link.