One of the most misused pieces of equipment when it comes to paranormal research is the EMF Meter. Here are the basics on just HOW these meters operate and which one you need for your investigations.
Since this is a question that comes up from time to time I have decided to address it here in the Q and A section.
To begin, a brief understanding of how an EMF field behaves is essential to understanding the best means of detection. To begin consider the difference between an electromagnetic field and a conventional magnetic field from a permanent magnet. Both are similar; they radiate from a single point of origin, they form a field much as shown in figure 1.
The major difference is that while the magnetic field is fixed, the EM Field originates from a varying source; it is constantly changing in its strength and polarity. This creates a problem with detection. A simple compass needle will respond well to a steady state magnetic field but the rapidly changing states of an EM field will render it quite useless. For those we need a different detection method. Enter the EMF Meter or EMF Monitor.
These devices detect a changing field by several different methods. Some use Hall effect sensors, some use inductive pick up, others use flux gate technology. It is beyond the scope of this article to address the difference between them, but suffice it to say that the major criteria has to do with the frequency of the EM Field being sensed. For most general purpose detectors we will encounter as researchers the inductive pick up is most common. That is the one I will concentrate on in this discussion. This consists of a coil of wire wound around a core. This core can be either air (higher frequency applications) or a ferro-magnetic material such as iron or ferrite. (Audio or low RF frequencies)
One question that soon arises is single axis or triaxial detection. A coil of wire is directional; the output from the coil will depend on the position of the coil with respect to the field. See figure 2.
Figure 2 - Single Axis Sensor
Clearly if a single coil is used the position of the detector with respect to the field is crucial if a reliable measurement is to be made. What is shown in Figure 2 is considered a single axis detector and is common to many cheap EMF meters. The output will be directly dependent on the position of the detector, and since we can't know the orientation of the field ahead of time, measurements can become problematic. The orientation will directly influence the observed strength, even if the field strength remains constant. There is a way though to eliminte this consideration and make the detector immune to problems related to positioning. That solution is the Tri-axial meter which uses three coils mounted as shown in figure 3.
Figure 3 - Triaxial Sensor
When the field insects these coils their output is added algebraicly to each other. Thus if one coil is off axis its output is reduced while the others will compensate since they are on a different axis. Regardless of positioning the coils will always add up to the same output level making this sensor immune to positioning errors.
Another concern has to do with the strength of the field. EM Fields follow the inverse square laws of physics. That is, the strength of the field is reduced by the square of the distance from the source. This simply means that the distance the meter is from the source will determine the intensity of the field it detects. As a result the reading from a meter does not determine the absolute strength of the field being generated contrary to what many paranormal researchers claim. A given reading could be from a weak source nearby or a much stronger source a greater distance away. And since in most cases involving paranormal research we don't know the source location the number is meaningless! It only tells us the strength of the field the meter is encountering, not the absolute strength of the field.
When dealing with EM Fields we also have what are referred to as natural EM Fields. These are generated by the earth itself, as well as solar fields which strike the earth. Most of these are low frequency, sometimes varying over a period of minutes or hours. These are sensed by using Hall effect or flux gate sensors rather than inductive coils. Many cheap EMF meters do not respond at these low frequencies making them useless for this purpose.
Portability is also something to be considered. Most people want to carry their meters around with them. But this opens us to problems. Simply moving a single axis meter will cause the natural fields to vary in direction thus causing false positives. The electric fields of any people nearby can also cause false activations. Triaxial meters are less likely to false alarms caused by movement, but they too can be activated by people moving nearby.
When it comes to the user interface, perhaps the display is the most critical item. LEDs provide very limited resolution. A meter movement can show minor deviation much more precisely than a series of blinking lights! A slight deviation on an LED detector would probably be missed. Of course the LEDs are much more visible in the dark than the unlighted mechanical meter. A solution here is the back-lighted LCD display with a numeric readout. The changing value displayed is easily seen even in the dark. However even this number requires interpretation to determine if the value is going up or down. For quick read out the analog meter movement is still generally preferred.
One final note. Often a claim is made for LED indicators that a spirit can communicate using the method of turning the lights on or off. There is no conclusive proof that any paranormal activity, with the exception of a few rare UFO sightings, can influence EM Fields in any way. Thus no such activity seen on KIIs, Ghost meters, or other such EMF detectors has ever been proven to indicate spirit activity. These are EMF meters, not ghost detectors!
Which brings us back to the original question, What EMF meter do you recommend for paranormal researchers?
As I have stated elsewhere on this site I prefer to use the EMF monitor approach rather than a meter since I feel it is easier to determine the source of the field by hearing it rather than measuring its strength. But if I have to use a meter I prefer the Alpha Lab Trifield meter for general applications. It will not cover natural fields, however when used in conjunction with the Trifield Natural both ranges can be covered. I would use two meters if I wanted complete coverage of both. The Natural would be kept stationary; the Trifield would be the one carried about if required.