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Electromagnetic Field Meters
EMF is the field of force associated with electric charge in motion, having both electric and magnetic components and containing a definite amount of electromagnetic energy. From WikipediaThe electromagnetic field is a physical field produced by electrically charged objects. It affects the behaviour of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces of nature (the others are gravitation, the weak interaction, and the strong interaction). The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field. The way in which charges and currents interact with the electromagnetic field is described by Maxwell's equations and the Lorentz Force Law. From a classical point of view, the electromagnetic field can be regarded as a smooth, continuous field, propagated in a wavelike manner, whereas from a quantum mechanical point of view, the field can be viewed as being composed of photons In our daily life we encounter electromagnetic radiation or electromagnetic fields, commonly referred to as EMF. The Electro Magnetic Field is found anywhere that electricity is in use or near any object that has an electric charge. EMFs are invisible lines of force that surround all electrical devices (appliances, computers, televisions, broadcasting antennas, power lines, rushing water, etc.) and wiring. Any time an electric current runs through a wire or an appliance, it produces an EMF. Electromagnetic radiation from Extremely Low Frequency (ELF), Radio Frequency (RF), and Microwave Frequency emissions.
One should also consider that the human body is a complex energy field that is constantly changing, also called Elector Magnetic Fields. Science has proven that everything and everyone has a certain vibration or energy field. Through experimentation we have learned that different people emit different levels. While some register very high with the various meters, most do not. When establishing the baseline readings, include a reading on the investigators.
As related to researching the paranormal, general consensus is that the fields are disputed when ghosts or spirits are in the area. While we cannot prove that ghosts cause EMF radiation, we have found where hauntings occur, we also document higher EMF readings. A field generated by a combination of electric and magnetic energy that radiates from radio and light waves to gamma and cosmic rays. It is believed that a ghost or spirit may use or manipulate these fields to manifest or to move items in our physical world.
What is the difference between a single axis and a three axis meter
An AC magnetic field is oriented the same way a regular bar magnet is, only the N-S fields are constantly switching at a given frequency (50/60 times per second for powerlines). A current will only be created in an inductor if the magnetic field poles are pointing almost the same way, meaning the magnetic field lines are oriented the same way as the coil. Here's the most important thing to remember - magnetic fields are VECTOR fields! This means that a magnetic field has not only a strength to it, but also a direction as well. A good analogy to help you visualize this is the wind - it has not only speed, but also direction. If you were trying to accurately measure wind speed, your wind speed meter's axis would have to be facing the wind - if it were angled another way, your reading wouldn't be accurate. This applies to magnetic fields as well - the meter's measurement axis must be oriented the same way as the magnetic field lines to get an accurate vector reading.
A single-axis meter has only one inductor, therefor only one axis to read on, so you could be right on top of a strong AC magnetic field, but if your meter's axis is facing at another angle, it may not even register on the meter. A single axis meter only gives the vector field strength along the axis in which it is oriented (most meters will say how the axis is oriented on the meter in the manual). If you're not sure of which angle will give you the right reading, then slowly rotate and tilt the meter at all angles, and the spot that shows the largest reading is where you need to be to get an accurate vector field reading. Remember that this angle/tilt will change depending on where you are - so you'll have to repeat this every time in order to get an accurate vector field strength reading. If you want to calculate a mean RMS field strength reading, then take one reading in a horizontal direction, then turn your meter so it's at a right angle to your last orientation, but still horizontal, take another reading, and then hold your meter in the vertical position and take a reading. The RMS mean (or more appropriately for vector fields, the "magnitude") is calculated as the square root of the sum of all three readings squared, i.e. F = (X^2 + Y^2 + Z^2)^[1/2]) (X, Y and Z are your three readings). If this sounds a bit tedious just to get a simple magnitude reading (because it does to me!), then I suggest you invest in a three axis AC EMF meter. A three-axis meter has 3 inductors, one on the X axis, one on the Y axis (perpendicular to the X axis), and one on the Z axis (perpendicular to both the X and Y axis), so no matter what the orientation of the EM field or meter is, you will still get an accurate reading. These meters don't give the vector field strength reading, but the TRUE magnitude reading, calculated by the Pythagorean theorem, as shown above (field magnitude F = (X^2 + Y^2 + Z^2)^[1/2]), so regardless of how the meter is oriented, it will give an accurate field magnitude reading. Ok, there it is, a grossly in-depth analysis of AC EMF meters, how they work, their frequency response, and their limitations. Futher down the page you'll find an in-depth comparison of many common AC EMF meters and advantages/drawbacks for each one. This should have answered almost any of the questions you may have had prior to reading it, but in case it didn't, I'd be happy to answer any questions. Just e-mail me at nprgtechdept@yahoo.com and I'll do my best to answer any intelligent questions you may have.
Here are some different EMF meters
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The Cell Sensor EMF meter has a base unit with a small probe that can be attached. When the probe detects EMFs the base unit will sound an audible alarm, the red portion of the meter will flash and the needle will register the amount of milligauss detected.
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The Gauss Master A higher level than the E.L.F. Zone as to sensitivity, this meter registers changes with a needle and an audible tone. An to read gauge, an audio signal and auto shut-off make it simple to use. Hand-held, light-weight and durable, with two easy to read scales.
The Gauss Master requires hands on, although on several occasions with the meter in the case or sitting idle has registered on it's on. |
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Gauss Master EMF Meter, a single axis meter, again a hands on unit. This meter must be rotated during use to find the area of the magnetic field being measured to acquire proper readings for situations needing high resolution measurements of AC magnetic fields. Large LCD display is easy to read in lighted situations. A pen light/flash light will be necessary if the area is dark. |
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The TriField Natural EM Meter was designed to do field measurements for special research. It detects changes in extremely weak static electric and magnetic fields, and signals with both a tone and the movement of a needle-type gauge if either the electric or magnetic field changes from previous levels.
This meter offers magnetic, electric, and radio/microwave detection in one package. This enables you to filter out false EMF levels from normal sources. The TriField is extremely sensitive to movement and vibration. This unit can be set and placed in an area without supervision. The tone change will alert to a possible disturbance. |
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Here is a comparison chart of some meters I found and researched on the web.
Note we as of now do not sell any equipment . Prices are based on information from many different sites.
Approximate peak sensitivity frequencies, measurement styles, and special features for common AC EMF meters are listed in the table below.
| Meter | Price | Frequency Weighted? |
Peak Sensitivity Frequency |
Measurement Style | Other Features |
| ELF Zone | $13 | YES | Unknown | Vector (One Axis) | None |
| ElectroSensor | $25 | YES | 200 hertz | Vector (One Axis) | LED Bargraph Readout |
| Gaussmaster | $35 | YES | 5,000 hertz | Vector (One Axis) | Audible Tone |
| CellSensor | $45 | YES | 150 hertz | Vector (One Axis) | Measures RF Fields |
| Multidetector II Profi | $100 | YES | 350 hz (LP), 1 kHz (HP) | Vector (One Axis) | Bandpass Filters, Measures Electric Fields |
| TriField | $130 | YES | 1,000 hertz | Magnitude (Three Axis) | Measures RF & Electric Fields |
| TriField* | $130 | NO | N/A (nonfrequency-weighted) | Magnitude (Three Axis) | Measures RF & Electric Fields |
| TriField Natural | $180 | YES | lim(x->0)x hertz | Vector (One Axis) | Measures RF & Electric & ULF Fields |
| UHS Meter | $279 | NO | N/A (nonfrequency-weighted) | RMS Magnitude (Three Axis) | Digital Readout, Bandpass Filters |
ElectroSensor ($25) - This meter is a very inexpensive solution if you are looking for low resolution AC EM field strength readings. It will measure from 1.5 to 30 mG, on a 10 LED bargraph style readout. This meter is especially useful if you are monitoring an area with video equipment - use a rubber band to hold down the "ON" button, and stand the meter up in front of the camera. Any transient EM fields will be easily visible on the video because of the LED readout. This meter is recommended for use in front of video cameras, but not for use as a handheld meter.
GaussMaster ($35) - For an inexpensive handheld meter, I would recommend the GaussMaster. It has an audible tone whose pitch gets higher as the AC EMF field strength goes up, and has an analog readout, selectable between 0-1 mG and 1-10 mG. The analog readout gives it a little more resolution than the above meters, and its frequency response is very broad. Essentially, its frequency response extends to about 20 kHz, which makes it useful for measuring a wide range of frequencies. Because of its higher peak sensitivity frequency, it is important to note that this meter is frequency weighted, so field strength readings outside the 50/60 Hz range won't be very accurate.
CellSensor ($45) - This meter wouldn't be my first choice for a handheld meter, but because it can measure RF fields as well, it might be useful to some people. This meter has a light and "bong" sound corresponding to the field strength, but I prefer the GaussMaster's tone output. But, for an inexpensive meter that will not only measure ELF AC EMF fields, but also RF fields, this meter would serve you well.
Multidetector II Profi ($100) - This is a VERY multipurpose meter, that I would recommend to anyone. It will measure not only AC EM fields, but Electric fields as well, both on a LED bargraph. The meter also has frequency bandpass filters - allowing you to select which frequency range you want to measure in (LP = 5-500 Hz, HP = 500-400,000 Hz) for both Electric and AC EMF. Also, this meter has a very broad reading range - you can measure AC EM fields up to 100 mG, and Electric fields up to 1,000 V/m. The only drawback is that it is only a one axis meter, and there are only 11 LED's, which means lower resolution (but sensitivity switches help keep resolution up). As described for the ElectroSensor, the Profi could be used stationary in front of a video camera, or also works great as a handheld meter.
TriField ($130) - This is a great meter for those of you looking for a multipurpose three axis AC EMF meter. It is the most inexpensive thee axis meter I could find, but for the quality of this meter, it is worth well over $130 in my opinion. This meter will measure not only AC EM fields, but also Electric and RF/Microwave fields as well, on an analog scale. Maximum measurable fields are 100 mG for AC EMF, 1,000 V/m for Electric fields, and 1 mW/cm^2 for RF/Microwave fields. Other than the possible desire for a digital readout (which is achieved by the UHS meter), I couldn't find any drawbacks to this meter. By default, this meter is sold as a frequency-weighted meter
TriField Natural ($180) - This is a VERY unique meter, as it does not measure the same EM frequencies as the other meters on this page. Most meters measure EM fields from about 20 hertz to several kHz, but this meter is actually designed to zero out the surrounding static (0 hertz) field, and measure any minute changes within that field (in both electric and magnetic fields). Because the meter needs to zero out the surrounding field, it MUST be used in a stationary position (if you're holding the meter, then the surrounding field is always changing, and the meter won't be able to stabilize). Some people report that they can walk with the meter - but they're missing the entire point of having this meter, and essentially all of their readings will be wrong. It also has a SUM setting, that will combine any changes in electric or magnetic fields into one reading - but I don't recommend using it, because if the meter goes off, you don't know which field really changed, and what good is that in research? The TriField Natural is calibrated at 2 hertz, and will measure changes all the way down to lim(x->0)x hertz (basically, anything *slightly* above 0 hertz, but not 0 hertz). Be careful on the electric field or SUM setting, because your body will easily distorts/create its own electric field that will set the meter off. On the magnetic setting, basically just find a good spot for the meter, set it down, and leave it. Once the reading settles to 0, you can adjust the "tone" knob until it starts sounding, then roll back on the knob just a little bit until it stops (that way, any small field change will be accompanied by an audible tone). On the magnetic setting, as long as you don't move the meter, or get any magnetized objects near it, it should stay fairly stable (meaning, your body alone won't set it off). Another important thing to note about this meter is that it is NOT a three axis meter, as many seem to believe, it is a one axis meter (the axis of sensitivity is along the length of the meter). The TriField Natural Meter will also measure RF/Microwave fields directly (the antenna sensor is located at the top/head of the unit).
UHS Meter ($279) - The Cadillac of EMF meters - the UHS three-axis AC EMF meter from AlphaLab, Inc. This is the best meter I've ever used - it gives highly accurate, non-frequency weighted three axis magnetic field strength readings. Unlike other meters, this meter is accurate enough to use in laboratory settings, and sturdy enough to use in the field. It features three settings for excellent resolution - under 20 mG, 200 mG, and 2,000 mG (yes, it will measure up to 2,000 mG!). It also has different frequency settings - from 13 to 1,000 hertz, and from 1 kHz to 75 kHz, or a combination of both frequency ranges. This meter is definitely the most accurate and reliable meter I've ever used, but it's definitely not for beginners. If you want highly accurate AC magnetic field readings this is the meter for you!
Hopefully this should help you select which meter is best suited for your needs - if you have any more questions e-mail me at nprgtechdept@yahoo.com