http://silentvoicesparanormal.com/web_images/trifield100xe.jpg
And the instruction manual is here:
http://www.trifield.com/UserFiles/TF100XE2011%20pdf.pdf
If the knob is on the “0-3″ position, the measurement has to be read on the central scale (as the instructions point out).

Some time after this bad reading, he said that the needle was back at zero and again, I went to look at the image and I noticed that the knob had been turned on the “Battery test position”…
At this point, we can speculate about the possibility that all the “anomalous” readings they got were just “falsified” (who knows if it was intentional) because they’re just reading the wrong scale. In an episode they said they’re reading a “20-25″ milligauss, but if the knob would have been set as it happened to be in this particular episode on the “0-3″ range, the correct reading would have been 2.5 milligauss. So, at the present time, we cannot be sure about the correctness of all the measurements they did with this instrument.

Again, since this is a very sensitive meter, if you wave it around, you could also get interference from the Earth’s magnetic field thus producing false readings that would be particularly spectacular if you run the instrument in the “0-3″ range.

To summarize a little: I think that their approach can hardly be defined as scientific: the way they’re collecting data is just wrong because they’re unable to use the instrument as it was designed to be, and I think it’s hard to believe that they’re doing it in a non-intentional way since it doesn’t take a scientist to understand that if you set an instrument to display something in the “0-3″ range, you have to read the 0-3 scale and not the 0-100 one.
If you see the episode of Poveglia, you’ll see that Zak is again misreading the instrument (http://www.youtube.com/watch?v=NUNH_00SWvk and jump to 0:21 – 0:22): you’ll notice that the knob is rotated on the “0-3″ setting, while he’s saying he’s getting a 3.5…the correct reading, given the 0-3 range, would be 1.1mg…

Another thing that struck me was the investigation in Poveglia Island. I live in Venice since I was born. In elementary school and in the first years of high school they teach you “History of Venice” and a great deal of time is dedicated to the history of the islands in the lagoon. Poveglia has never been home to a psychiatric hospital as there were two islands not far way from her, named San Servolo e San Clemente, which housed psychiatric institutions: the first was an all male psychiatric – forensic hospital that now has been converted to serve as a campus for the university, the second was for female patients and now it has been renovated and is a 5S stars luxury hotel. Poveglia was home to an infectious disease hospital as well as the island named “Le Grazie” which housed an hospital until the end of the 1970s.
However it is correct to say that in ancient times, Poveglia was used to dump the bodies of the infected by the plague.
I was also impressed by the possession of Zak while they were inside the hospital: when he yelled at Aaron he used the same words (translated in english of course) that you would find in this article that is written in italian:

http://www.italos.it/italia/miti-e-leggende/poveglia-l%E2%80%99isola-maledetta.html

At the end of the article there’s a line written in bold which says that a person who went into the hospital heard an invisible voice saying: “Get out of here and never come back!” If I understand correctly what Zak yelled at Aaron, he says “Get the f**k out of here!”. So, given the fact that this words are allegedly what the mad doctor speaks to whoever enters his hospital, it could be a perfect staging since it would have taken GAC grew a little googling to find this story and then to stage the possession.

Anyway I think that the fact that the em readings are systematically falsified by an incorrect use of the instrument is a partial proof that GA is, scientifically speaking, inconsistent. Since I have no access to the other instruments they’re using (i.e. their customized digital em meter, the spirit box with the dictionary inside, etc) it is not possible to say that all of GA is fake, but I think we can say that the readings produced by the analog trifield meter are meaningless, since the device is badly operated.
They could produce scientific strong evidence if they use a frequency counter together with the trifield: in this way you can easily tell if the field that is making the needle jump is artificial or is paranormal in nature (i.e. if you get a spike and the frequency counter displays a 60Hz frequency, you can say that the field is produced by an electrical appliance, a power line and so on)…since the frequency counter is cheap compared to all the other “gear” they use, I wonder why they don’t purchase one to actually back their evidence.