portable "ghost detection" devices are now available to the paranormal investigator.

Electromagnetic Field (EMF) Meters
    Anomalous electromagnetic field readings are often recorded in haunted areas.  Varying levels of electromagnetism are normal, generated by electric appliances, wiring, overhead powerlines, and the like.  Normal electromagnetic fields need to be isolated and ruled out -- though it should be noted that some researchers, including William Roll, believe that strong artificial sources of EMF can induce or aggravate poltergeist activity.
    Paranormal EMFs are untraceable, fluctuate in intensity, and typically move from one spot to another.  They often occupy specifically defined areas of isolated, suspended space, as opposed to emanating from a structural surface.  The locations of these pockets may correspond to the exact areas where a psychic claims to see an apparition.  Their location and intensity can both be logged by hand-held magnetometers.  One low-cost unit, the Tri-Field Meter, is routinely used by ghost investigators.
    Strong EMFs can also affect magnetic videotape, causing interference bands and resulting in strange glowing or fogged images on tape that were invisible to the naked eye.  Similar sound distortions, as well as strange voices (EVP, or electronic voice phenomena), can show up on magnetic audio tracks.

Radiation Meters
    Abnormally high readings of gamma radiation have been detected at some haunted locations.  In some cases, Geiger counter probes have recorded significant localized increases in ionizing radiation where a psychic claims to see a ghost.

Thermal Imaging
    Thermal imaging cameras, developed for the medical and manufacturing fields, record and display images of objects based on their heat output, as opposed to their ability to reflect light.  Using a false-color imaging template, colder areas show up as darker colors and warm areas as lighter colors, registering temperature variations as small as one degree Fahrenheit.
    Investigators first used thermal cameras in haunted houses to record the anomalous cold spots that they often encountered.  An unexpected development has been the detection and filming of unexplained hot spots, both stationary (on a structural surface) and freefloating.  As with EMF and ionizing radiation fields, these hot spots often correspond with the exact location a psychic will see or sense an apparition.

here are two ways to spot a ghost:  1) wait for one to float up your basement stairs and say "boo," or 2) get the latest equipment and start ghostbusting.  For more than 100 years, professional paranormal investigators and the merely curious have looked for the edge that would help them hunt this most elusive game.  With recent technological advances, Casper may be in the cross-hairs.

Scientific ghosthunting devices first appeared on the scene in 1882, when the Society for Psychical Research was founded in England.  While the introduction of the scientific method heralded the use of investigative tools such as controlled experimentation and photography, the state of the art in paranormal investigations remained fairly stagnant for the next hundred years.  Investigators relied mostly on psychics and eyewitnesses.  These approaches, while valid information-gathering techniques, leave much to be desired from an evidentiary point of view.  Primitive scientific equipment did exist, and it was capable of monitoring and documenting anomalous phenomena, but size, portability, and expense kept such devices out of the hands of field investigators.
    The field changed dramatically in the 1980s with with rapid advances in microchip technology, computer miniaturization, and dramatic price decreases in high-tech equipment.  As new scientific tools were developed to detect environmental changes -- mainly for the medical, electronics, and safety industries -- paranormal investigators started using them at haunted sites.  The practice of using different monitoring and recording devices is based on the assumption that any object or force that interacts with our physical environment will alter that environment in some way.
    Several years of experimenting have taught us that unusual measurements can be documented at many haunted locations.
    While we have yet to develop a definitive specter-detector or poltergeist energy meter -- mainly because we are still not sure what ghosts are made of -- a wide range of practical and