What is it? The big answer is the electromagnetic spectrum. This is the range of all possible electromagnetic radiation. At the low end of this, meaning 1 Hz, we have brainwaves. At the high end, in the 10^20 Hz (10 to the 20th power), we have gamma rays, which can give you a healthy glow. This is a very large theory and gets complicated. Fortunately, we are only concerned with a specific range in this spectrum.
The low end of the emf spectrum is where we play. This is the zone between 1Hz and 10,000Hz. This is classified by several abbreviations including: LF - Low Frequency; 30kHz, VLF - Very Low Frequency; 3kHz, VF - Voice Frequency; 300Hz, and ELF - Extremely Low Frequency; 30Hz. Most emf meters are calibrated to pick up fields at 60Hz. This, of course, is standard electrical frequency in America.
The fields themselves come in two flavors: Electric and Magnetic.
Electric
Electric fields are created by voltage. Higher voltage means a stronger electric field. They are often present in electrical equipment as long as it is connected to a source. Their intensity decreases quickly over distance, and they are easily blocked by conductive material. This includes the human body. The electric field strength is measured in volts per meter (V/m).
Magnetic
Magnetic fields are created by current. Increase the current, and you increase the field. Most electrical equipment must be on to produce a magnetic field. A notable exception to this is a “wall wart” power adaptor, which will emit a magnetic field as long as it is plugged in. A field will be stronger if a device is set to it’s “high” setting and weaker at a “low” setting. Field intensity decreases over distance just like electric fields. Unlike electric fields, magnetic fields are not easily blocked and are difficult to shield. This contributes to the link between magnetic field exposure and health risks. Magnetic field strength is measured in units of gauss (G) or tesla (T). 1T = 10,000G. A common measure is the milligauss (mG) or 1/1,000 of a gauss.
So, now that we have some basic terminology and an idea of what emf’s are, lets take a look at how we detect them. The tool that does this is an emf meter. There are many different kinds of meters. The one that I will discuss here is called the AC Gaussmeter. This meter is specifically designed to measure magnetic fields. Typically they are calibrated to pick up fields at 60Hz and therefore detect fields given off by common household electronics. AC Gaussmeters come in two types: single axis and triple axis. This refers to the position of the sensor located inside the meter.
Single Axis
A single axis meter contains a single sensor. Because magnetic fields are oriented in space, a single sensor will only detect the field properly if it is aligned with the field. To get a correct reading with this type of meter, you must rotate the meter until you find the maximum reading. If the meter is turned 90 degrees from the maximum reading, it will read almost zero. This kind of meter is inexpensive and good for finding the orientation of a field. If used in a general sweep of the room, it’s limitations become obvious. You will not get accurate readings unless you spend time rotating the meter in specific areas.
Triple Axis
A triple axis meter contains three sensors. These are aligned at right angles to each other. This allows the meter to always align with any field it detects, no matter how it is oriented. These meters tend to be more expensive than the single axis variety. For a general sweep of an area, it will find fields quickly, and give an accurate reading no matter how it is oriented.
What does this have to do with ghosts? As I stated before an emf meter alone cannot prove the existence of a ghost. It can, however, eliminate other explanations. It’s power to debunk the supernatural is it’s greatest asset. When visiting an investigation site, it is wise to do an initial sweep of
the place with an emf meter. This tells us where the fields are and gives us good baseline readings. It allows the investigator to become familiar with a site. We can find where the exposed outlets or unshielded wires are. Many times a strong field is found where people claim to have paranormal experiences. It has been found that exposure to strong magnetic fields can alter perception and gives a reasonable explanation that debunks the presence of a ghost. It is important to remember that these meters are designed to pick up man-made electrical fields. Any reading should first be attributed to this, before jumping to an unsupported conclusion. Having stated this, during an investigation, unexplained spikes in the emf where baselines have been established warrants further investigation. This could indicate the presence of a ghost. Unexplainable emf readings can lend support to other forms of evidence and reveal the presence of the paranormal. If all other reasonable explanations have been explored, we may have something.