EMF Meters
EMF - Electromagnetic Frequency...meters that measure the electromagnetic frequency are some of the most popular tools used by investigators. It is believed that manifestations cause a disturbance in the EMF field, and can sometimes be measured by these meters.
There are a lot of EMF meters out there to choose from. Some are very expensive, while others are pretty cheap. Your choice will depend upon how deep your pockets are and whether you want just an indicator of possible activity or more detail on the disturbance, how strong it is, and so forth.
The ELF meter and the KII meter have come to be viewed as having the ability to facilitate communication with spirits that may be around, through a question and answer session, with the spirits causing the lights to light up in direct response to the questions given. While it certainly cannot be proven beyond any shadow of a doubt, the results some groups have obtained are very interesting, and it should be an area of further study.
There are two types used in most investigations. One is a single axis, which gives results depending upon which direction you are pointing it in. The other is the triple axis meter, which can measure results from multiple directions at once. While the triple axis can give you a better overall reading, it is also much more sensitive, and therefore tends to be better used as a stationary measuring device, while the single axis works well being carried around with you.
The single axis meters are also much less expensive, and you will find that most groups or individuals will have several single axis meters and one or two triple axis meters, with the preferred triple axis meter being the TriField Natural EMF meter, as it gives a better reading of natural emf frequencies.
Compass
While not as 'glamorous' as an EMF meter, if you are mainly looking to track down any anomalous EMF's, and if you are on a tight budget, then a good compass may be just what you need to get the job done.
If the EMF fields get wiggy, you will see it cause the compass needle to move around, sometimes even spin if the field effects are strong enough. It wouldn't hurt to have one on hand along with an EMF meter, just to see how certain readings also affect the compass. And it gives you one more good measurement of any anomalies that do occur.
Digital Recorders
These are essential in obtaining EVP's - electronic voice phenomenon. These are used in most investigations, questions are asked, then the investigator waits to give any spirits that may be around time to hopefully answer the question.
The results have been amazing.
It's a good idea to get an external microphone to use with any recorder, not only to avoid recording the sounds of the inner workings of the device, but also to make it easier to capture evp's with the added sensitivity of an external microphone.
Thermometers
One of the most common and well-known side effects of a ghostly manisfestation is the drop in temperature. It is believed that spirits draw energy from the surrounding environment in order to manifest in some way, and that that causes the temperature to drop.
Other times, the opposite occurs, where the temperature actually goes UP in a small area, with no discernible cause.
In order to document this phenomenon, investigators use various types of thermometers to record the temperature in the investigation area. Digital thermometers are the most popular, and vary in cost much as the EMF meters do, from relatively cheap to very expensive models.
Digital Cameras and Video Cameras
Digital cameras are another standard tool used by all investigators. While film cameras are also still in use, the digital camera has become much more popular, due not only to the ease of use, but because you can immediately upload any images to your computer, and from there, share them on the internet.
Video cameras are also popular, in an attempt to try and capture any moving images of possible ghostly phenomenon. While larger groups can afford to have numerous digital cameras and video cameras to cover a ghost investigation, newer cameras now offer the option of being able to capture both still images as well as videos. The image quality of the videos aren't too bad, either, so combining two in one can be a good option for an investigator on a tight budget.
Dowsing Rods
Some scoff at dowsing rods, others totally embrace them.
I am somewhere in between.
Dowsing rods have been used for ages to find water, lost items, and other items. Their successful use has been documented many times, but many investigators shy away from them for fear of being labelled as frauds.
I plan on doing some testing of my own, to see if any results actually correlate with responses on EMF meters and other devices. If nothing else, it would be interesting to see what the results are.
Batteries, Accessories
You can never have too many batteries. It's almost a cliche', that possible spirit activity tends to drain batteries, even when they are brand new! So be sure to stock up!
Other accessories you should note that will certainly come in handy...
First Aid kit...you never know what you will run into, so having a good kit on hand to treat cuts and insect bites will be a good idea.
Tripods...to give you more options in setting up your video equipment, and produce more stable images.
Cases...to carry all your goodies in.
Flashlights...it does help to see where you are going whenever you are working in the dark. :D
Walkie Talkies...invaluable in being able to communicate with other team members on an investigation, without having to run all over finding each other. You can find good ones at Walmart or elsewhere, for very reasonable prices.
I'll add more as I check out some other items,like the Frank's Box or knockoffs thereof, and share any results I may get from those devices.