Electromagnetic Frequency or EMF refers to the field of force associated with electric charge in motion, having both electric and magnetic components and containing a definite amount of electromagnetic energy. Those who are seeking to make contact with entities and beings not of this world use EMF devices to detect their presence. 

The prevailing theory is that spirits and other supernatural beings disrupt the electromagnetic fields. There is also a theory that these spirits may also use or manipulate an electromagnetic field in order to travel through or move items in our world. Though these theories have been difficult to prove beyond a shadow of a doubt, most report a stronger than normal reading from EMF devices when in areas that are known for supernatural and paranormal activity.

Unlike electronic voice phenomenon or EVP, those who use EMF are typically more researchers than regular people. Since EMF equipment is fragile, and must be kept and maintained. If you are interested in EMF and ghost hunting as most researchers using EMF are referred to as ghost hunters, there are a few things that you need to consider.

Typically, if the disturbance remains constant without fluctuations it is probably artificial and could be easily explained as it appears that paranormal activity tends to be in constant motion. One of the most popular areas for hunting or investigating is a cemetery. If you choose to scan a cemetery, you may want to start at one corner and make your way across, keeping the EMF device about waist high. 

Be sure to document any background noise and any other possible disturbance that may give you a false reading.  Though EMF devices were not originally designed for investigating the supernatural, it has quickly become the biggest market for the devices. Despite the skeptics, investigating the paranormal by using EMF has a wide following, today. There has always been a desire to prove irrefutably the presence of supernatural beings and by using EMF, we are only getting closer.