Interaction?

This experience happened while in Edinburgh's Underground Vaults and if it is trickery I have no idea how he did it. It involves the use of EMF meters (as always not used for the actual purpose they should be and that is to measure EMF) and requests for interaction.
The investigator (who also claimed to be psychic) claimed there was a "spirit boy" in front of him and asked the boy to interact with the meter held in his hand by making it light up and make the alarm noise go off. Sure enough, it did so, at no point did I see the investigator manipulate the meter I was filming it at the time (as part of the investigating team) so I know this. Then the investigator said "Can you go and find another machine like this one and make that make a noise.) A second later and sure enough the other emf meter which was left on in the next room, went off. In both instances when he asked the "spirit" to stop the noise from the machine, the noise stopped almost immediately . When asked to start again, it started again. Then he asked the "boy" to come back and set off the machine in the hand again and it did so, this time when asked to stop, it didn't stop for at least 1 minute and eventually fell silent. All the people in the vaults were accounted for and the other machine was in view albeit in another room.
The investigator (who also claimed to be psychic) claimed there was a "spirit boy" in front of him and asked the boy to interact with the meter held in his hand by making it light up and make the alarm noise go off. Sure enough, it did so, at no point did I see the investigator manipulate the meter I was filming it at the time (as part of the investigating team) so I know this. Then the investigator said "Can you go and find another machine like this one and make that make a noise.) A second later and sure enough the other emf meter which was left on in the next room, went off. In both instances when he asked the "spirit" to stop the noise from the machine, the noise stopped almost immediately . When asked to start again, it started again. Then he asked the "boy" to come back and set off the machine in the hand again and it did so, this time when asked to stop, it didn't stop for at least 1 minute and eventually fell silent. All the people in the vaults were accounted for and the other machine was in view albeit in another room.