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B Electric field detector

  1. Feb 9, 2016 #1
    I bought this electric field detector that can detects minimum of 3V/m. It said the human body can emit electric field.. so the detector can detect the presence of someone on the other side of a wall. May I know how the human body can emit electric field.. and is a detector with a 3 V/m really sensitive? what other devices can detect such low reading too?
     
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  3. Feb 9, 2016 #2

    BvU

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    Experiment ! Use a 9V battery or something.
     
  4. Feb 9, 2016 #3
    External human generated electric field? I don't think so. In so far as the human body can accumulate an external static charge you could have a significant electric field but it usually dissipates except in dry conditions. The internally generated voltages are only of the order of 10's of millivolts
     
  5. Feb 9, 2016 #4
    I bought this Trifield Natural EM meter. https://www.amazon.com/Trifield-Nat...843&sr=8-1&keywords=trifield+natural+em+meter

    I brought it to a mall. When set to Electric Field. The needle can indicate reading when people walk 1 to 2 meters in front of it. The manual inside says:

    "When the dial is set to ELECTRIC, the meter is sensitive to electric fields as weak as 3 V/m (volts per meter). To illustrate just how feeble a field this is, a 10'x10'x10' room filled with a field of this strength has a total amount of energy equivalent to that required to lift a single grain of table salt 1/50th of an inch. Indoors, electric fields typically fluctuate 1 or 2V/m. By settting the minimum sensitivity to change at 3 V/m, we have designed the meter to disregard this "background noise". Human beings and animals usually emit an electric field which is easily detectable using the Natural EM Meter. In fact, the meter can be used as a motion-activated intruder alarm, depending on the type of wall and the charge on the person. It is so sensitive that it can detect the presence of an person through a wall. Though it is not foolproof in this capacity, (sometimes a person will carry no electric charge and thus be "invisible" to the meter), it's sensitivity is of interest to researchers."

    My question, does it mean my meter is detecting the total 3 V/m in a room or from a particular source? I use the meter to detect geomagnetic storm, etc.
     
    Last edited by a moderator: May 7, 2017
  6. Feb 9, 2016 #5

    BvU

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    Does you ghostmeter show approximately half a Gauss (50 ##\mu T##) for the earth magnetic field ?
     
  7. Feb 9, 2016 #6
    It is detecting the electric at that point in the room. the electric field in a real life situation is very inhomogeneous so measuring at one point does't tell you anything about the field elsewhere. The use of the term 'filled with a field of this strength" is meaningless the total the electric field content of a room is immaterial to the value at a given point and the force that it can exert on any electrified object.

    In the manual states that the instrument has a built in threshold set to disregard electrical field noise of up to 2 M/m and will give no reading less than 3 V/m I believe that the manual is using misleading language in stating that people "emit" an electric field. They correct this misstatement later by more correctly attributing the electric field to the electric charge that they might be carrying.

    Electric fields of an electrified person can be hundred of V/m depending on how close you are to them.

    Its ability to detect electrical storm is due to the electromagnetic field pulse sent out by the lightning discharge. AM radios receive this as loud static.
     
  8. Feb 9, 2016 #7

    sophiecentaur

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    Absolutely true. It could be exactly the same for a damp mattress or a log, placed in the same place as the human.
    The biggest electromagnetic effect that a human is likely to produce will be the dreaded Mains Hum, which you can get when touching the input to an audio amplifier. In a world with no mains electricity, your meter may not be quite as lively.
     
  9. Feb 9, 2016 #8
    This is also the part I wanna know. The manual states "On MAGNETIC, the meter reads any change in the magnetic field caused by rotating the meter in the Earth's magnetic field, by a moving magnetic object, or by DC currents carried by wires or the atmosphere. The earth's field strength is about 50 microteslas (500 milligauss), so rotating the meter from north to south rapidly (within a 0.5 second interval) causes a momentary reading of about 100 (a change from -50 to +50). If subsequently held still, the needle will settle back to zero. For the best readings of transient fields, the meter should be placed on a stationary platform because of sensitity to slight rotations while hand-held."

    So why does the meter not show the approximately half a Gauss (50 ##\mu T##) for the earth's magnetic field? Why do you have to rotate it to measure the earth's magnetic field??

    About it's being a ghostmeter. Well. I'm testing the theory that some dark matter configuration can emit slight electric charge. I have a friend who has developed the brain sensitivity such that when he closes his eyes. He can still see images.. in haunted house.. he can see figures moving around.. some researchers who use the meter on the figures has detected reading. Im thinking if its related to some kind of synesthesia.. where instead of people see colors.. they can map the electricified dark matter object in their brain and track it around. On living people. my friend can also track this thing around the body. So after death, the thing has simply separated and there is lesser cohesion and they are simply what you may call "ghosts". Of course I bought the meter to test the theory and debunk it. But first I need to learn how to detect normal objects electric field and earth magnetic fields.
     
  10. Feb 9, 2016 #9

    BvU

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    Good question. We'll have to ask the maker, for I have no idea.

    Just joking :rolleyes: .
     
  11. Feb 9, 2016 #10

    sophiecentaur

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    A simple meter will work on induced emf whilst the magnetic field changes. One way to change the field is to change the direction of the coil. Measuring a static field without moving a test coil is much harder and would require a Hall Effect device or an electron beam tube where charges are deflected..
     
  12. Feb 9, 2016 #11
    Do you know where to buy these Hall Effect device or particle beam tube?
     
  13. Feb 9, 2016 #12

    sophiecentaur

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    You can buy all sorts of Hall Effect units (try Google) but you would need to know the specification that you require.
    There are many electron tubes available (like CRT TV tubes and school demonstration equipment) but they would need to be part of a whole set of gear. Or you can buy a Magnetometer, which will cost you an arm and a leg, probably. Again, you would need to specify the performance you require. They are used all over the place to measure variations in the Earth's magnetic field, surveying archeological sites for instance. This isn't a subject I have ever been involved in and you would need to get expensive specialist advice, to choose exactly what it is that you need. (If you have any idea, that is)
    You say you have bought a device already but you don't exactly say what the application is. Some of your ideas are definitely not PF business. Your statement about "Dark Matter" is clearly nonsense as no one has actually laid their hands on a bucket of the stuff.
    Have fun.
     
  14. Feb 9, 2016 #13
    I tried a 9V battery.. it can't seem to detect it.. it's just detecting my fingers when I hold the battery close to the detector.. why.. what is the magnitude of electric field created by a 9 volts battery? I tried a comb in my hair and there is a reading as it has detected the electric charge in my comb.
     
  15. Feb 9, 2016 #14

    davenn

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    there wont be any externally detectable electric field until the battery is powering a circuit
     
  16. Feb 9, 2016 #15

    berkeman

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    Thread closed for Moderaton...
     
  17. Feb 10, 2016 #16

    berkeman

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    We don't discuss nonsense here. Thread will remain closed.
     
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