Ghost detectors

I see many shows about spirits and ghosts that show people with electric field detectors searching for ghosts. can anyone point me to a website or link that gives an explanation of how this works? I mean what proof is there that ghost would create an electric field?

Everything I can find is just illogical conclusions. For example, investigator goes into the house with gadget and finds a field in the room that they were told the ghost haunted.

I took one around my house and found odd fields were I would not expect it. But no one in my house has every seen or heard anything spiritual.

Can anyone provide some good evidence?