EMF

Dean using his homemade EMF meter in 1.04 Phantom Traveler.

EMF Meter Electromagnetic field meters (also called EMF detectors). Meters that measure the derivative (rate of change) of the surrounding magnetic field; thus, these meters are sensitive to changing magnetic fields (fields with a frequency above 0 hertz). Most EMF meters are most sensitive to frequencies of about 30-10,000 hertz, while some have a wider response. Paranormal investigators and ghost hunters use EMF meters while conducting investigations. Unusual activity in the form of high readings on these meters signifies that there is some type of paranormal activity, such as the presence of a ghost or other supernatural creature. – Pad of Definitions (1.04 Phantom Traveler), Official Website

The EMF meter is used to detect whether there has been a supernatural presence in an area. It was a gauge to indicate the intensity of the reading and makes a distinctive sound. An EMF meter was first seen in 1.04 Phantom Traveler:

Dean: It's an EMF meter. It reads electromagnetic frequencies.
Sam: Yeah, I know what an EMF meter is, but why does that one look like a busted up old walkman?
Dean: 'Cause that's what I made it out of.

In 1.04 Phantom Traveler, Dean uses the headphones on the Walkman to listen to it. By 1.11 Scarecrow, the outer casing of the Walkman has been removed, and the headphones are not used again. Dean built it to last - it is still in use seven years later, most recently seen in 7.13 The Slice Girls.

Note: A Walkman was a portable audio cassette player, available in some models with a radio, first sold in the U.S. in 1980.

Non supernatural readings from the EMF meter

The EMF meter in the episode 1.11 Scarecrow.

EMF (Electromagnetic Field) A physical field that is produced by electrically charged objects and which affects the behaviour of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction, one of the four fundamental forces of nature. The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field. – Pad of Definitions (2.18 Hollywood Babylon), Official Website

Any device that uses electricity emits some EMF. Most of them are shield and are too low to cause problems. But power lines and transformers are sources of extremely low frequency (ELF) that can jam the readings of the EMF meter from other, say more supernatural, sources.

From 1.17 Hell House:

Sam: You got somethin’?
Dean: Yeah. The EMF’s no good.
Sam: Why?
Dean: I think that thing’s still got a little juice in it. It’s screwin’ with all the readings.
Sam: Yeah, that’d do it.

From 4.11 Family Remains:

Sam: Needle's all over the place.
Dean: Yeah -- power lines.

From 7.13 The Slice Girls:

Sam: It's all over the place, redline. redline. Oh, and... power lines by the open window, where there's a breeze... that could have moved the papers.
Dean: Did you feel a breeze?
Sam: It doesn't matter, Dean. The readings are useless.

Episodes featuring the EMF meter

Sam using the EMF meter in the episode 7.04 Defending Your Life.

• 1.04 Phantom Traveler
• 1.11 Scarecrow
• 1.14 Nightmare
• 1.17 Hell House
• 2.02 Everybody Loves a Clown
• 2.06 No Exit
• 2.07 The Usual Suspects
• 2.13 Houses of the Holy
• 2.18 Hollywood Babylon
• 3.05 Bedtime Stories
• 3.14 Long-Distance Call
• 4.02 Are You There, God? It's Me, Dean Winchester
• 4.06 Yellow Fever
• 4.08 Wishful Thinking
• 4.11 Family Remains
• 4.13 After School Special
• 5.19 Hammer of the Gods
• 6.02 Two and a Half Men
• 6.14 Mannequin 3: The Reckoning
• 7.04 Defending Your Life
• 7.13 The Slice Girls
• 7.18 Party On, Garth
• 7.19 Of Grave Importance
• 8.06 Southern Comfort
• 8.11 LARP and the Real Girl
• 9.07 Bad Boys
• 9.14 Captives
• 9.15 #THINMAN
• 10.13 Halt & Catch Fire
• 10.14 The Executioner's Song
• 10.16 Paint It Black
• 11.05 Thin Lizzie

External links

SuperEMF meter screenshot.

• EMF Measurement at Wikipedia
• SuperEMF the Supernatural EMF meter for Android: an EMF meter for Android devices - The SuperEMF. It has a layout almost equal to the EMF used by Winchester brothers. It's available on Android market

Follow the description on Android Market:

SuperEMF is an EMF detector and with it you could track easily all paranormal activities with your Android phone. It uses a great layout based on the famous EMF device used by "Winchester Brothers" - Supernatural.