Residual 60 Hz magnetic intensity

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Why does it matter? What level and frequency has shown to have any real medical effect? Can you prove any biological effect or harm?

Tests have been done on this stuff for years. iEEE has extensive standards backed uo by tons of research data. Fir example have you seen what transmission li e workers do? The health effects have been studied both short and long term.


So, why does it matter?

Donate your PKE meter to the local ghost hunters.
Since I had essentially no background EMF, does that mean I don't have any ghosts lurking about?
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
But unbalanced wires are a problem. At my daughter's home my cousin's son was playing his electric guitar, and there was substantial unwanted 60 and/or 120 Hz hum. This was obviously a result of the unbalanced current path relative to the air conditioner.
There is a set of overhead MV conductors running through an easement next to my property, and I have a rehearsal studio in my garage on the side of the house nearest the wires. If I play my Stratocaster with a single pickup selected into a high gain amp it howls like a banshee at 60Hz. It is a challenge for me to get clean recordings.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220625-1342 EDT

I have now added an electrostatic shield to a portion of my magnetic sensor. Now there are areas in my back yard that I get down into the range of possibly 0.005 to 0.01 milligauss. Unfortunately I can not presently look at the waveform. The greatest resolution of my AC meter is 10 microvolts. There is definitely directionality to the fields I am seeing.


ptonsparky:

Since you are getting rather high level readings out in the wide open spaces I suspect you have an instrumentation problem. Meaning the meter itself, or noise of some sort.


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gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220625-1925 EDT

ptonsparky:

I believe that if you are out in the wide open spaces without close by conductors that 1 milligauss would be high. That is high only in what I might expect to read. Does not necessarily mean that it is a problem. I expect at the moment that you may have an instrumentation problem.

With my present probe I will drive around out the country away from power lines, and see what I read.

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ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
220625-1925 EDT

ptonsparky:

I believe that if you are out in the wide open spaces without close by conductors that 1 milligauss would be high. That is high only in what I might expect to read. Does not necessarily mean that it is a problem. I expect at the moment that you may have an instrumentation problem.

With my present probe I will drive around out the country away from power lines, and see what I read.

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I did not zero it.
Fluke 87 on millivolt. 1 millivolt=1 miligaus
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220625-2335 EDT

ptonsparky:

What device did you use to get millivolts out from a magnetic field, and that would require a zero adjustment?

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ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
The 1st over scale was at home transfer switch, basically between the two hots. Max was at utility meter. I started roughly 100 feet North of house. Overhead Utility primary and transformer is about 250 Southwest of house. Last few blips are at a pole guy wire as I bumped it.

I zeroed the 87 where I started with the 43 and retraced the route. not enough difference to make note.

Gar, my equipment is not on the same playing field as yours. Nor are my skills

You asked. I provided with the best I have. If you want me to change meter settings more suitable for your needs, let me know
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220625-1044 EDT

ptonsparky:

If I put a Fluke 87 in AC voltage mode, and the range is set to 200 mV, then I will get a very low reading with the meter input shorted. I don't have one at home so I can't verify its AC reading with a shorted input. At home I am using a Beckman 4.5 dight with about the same specs as the Fluke 87. The Beckman has no user adjustable zeroing for either AC or DC, and my memory is the same for the Fluke. The Beckman fluctuates between 0.00 and 0.01 mV in AC mode with input shorted.

Hall device probes for magnetic field strength sensing are quite noisy at low magnetic field strengths.

For my measurements I am using a tuned to 60 Hz magnetic coil sensor. For calibration I use a straight piece of wire with 1.5 A and 60 Hz thru it, and measure the signal level from my probe at a 1 meter radius from the wire. The reading is about 8 mV. From my previous equation this means the field level at 1 mV is about 3/8 or about 0.4 mG for a 1 mV reading. In my backyard 30 ft or so away from most current sources i may read in the range of 0.01 to 0.03 mV at the moment, or about 0.01 milligauss. Under my 3 phase delta primary lines ( no neutral ) the reading is about 0.4 mV or about 0.2 mG.

I would go out in one of your farm fields and see what you read.

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gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220625-1745 EDT

ptonsparky:

Why would you use the REL mode?

In straight AC mode there is an input capacitor in series with the meter. Thus, any DC components superimposed on top of the AC signal are stripped away.

You want to be in straight AC mode. Shorting the meter leads will produce a meter reading of very close to 0.00 mV.

Now if you connect the meter to the magnetic flux sensor, you are in a very low flux field, and the meter reading is much above what is expected, then you can assume that you are in some sort of field with a high noise level, either in the measured field or in your sensing equipment.

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paulengr

Senior Member
One of our forum mods, Karl Riley, wrote the book on EMFs and invented a gaussmeter. His research indicates high levels of EMFs are caused by electricians making wiring violations of the NEC. Search for his video on you tube.
Are you familiar with the inverse square law?

Quite aware. My undergrad was in communication systems. Then I went on to do large industrial systems.

The biological effects have been studied and quantified for years. The limits are set roughly 10 times lower than measurable effects as a safety margin.

To equate this with power systems has two problems. First off most of the utter crap you see uses constant values intended for exposure to microwaves. Why? Because of wavelength. The speed of light is 2.98 x 10^8 meters per second. So if we start with say 10 Gigahertz (10^10) which is on the order of a kitchen microwave oven we end up with a wavelength of 2.98 cm or about 1.2 inches. When a wave hits a conductive object that is substantially larger than 1 wavelength it is either absorbed or reflected.m essentially 100%. On the other hand if a conductive object is less than about 10% of the wavelength most of the wave just passes right through, unaffected. So if a human is exposed vertically with an average length of about 2 meters, wavelengths of 20 meters or more barely interact at all, or about 15 Megahertz. For reference, 60 Hz wavelength is 4,967 kilometers or around 2750 miles. So I really don’t care what a gauss meter reads unless it also takes wavelength into consideration.

Put another way, there is actually an ELF transmitter, the largest radio transmitter in the world. It was featured in the movie Hunt for Red October but like a lot of Tom Clancy stuff, it is real. The operating frequency is somewhat secret but it is close to 60 Hz and in the ELF range. The antenna is much shorter than the owner really wants which makes the efficiency terrible but since it spans two states already over hundreds of miles, it’s about as big as it can reasonably get. The effects on local biology have been extensively studied. Other than the fact that plants seem to grow slightly faster in the area, no other effects have been measured. The power level is also secret but it is far more substantial than even several dozen houses combined. I lived in the area and went to the major engineering university in the area. I have read several reports on the system because hey…engineer aspiring to work on communication systems.. I had a big interest.

The point is that ELF has vastly higher power levels and thus your inverse distance concern is trumped by massively higher power and a much, much larger antenna gain. And even then if the measurable biological effects from the worlds largest ELF system dwarf a residential system yet seems to have no measurable effect on local biology, to put it mildly there is simply no scientific evidence to support all the crazy claims of people somehow being affected. It’s all psychosomatic crap.

I do believe in “stray voltage” of sorts. It does exist around multi grounded systems. Mike Holts group has done a lot to dispel myths. And yes cows are more sensitive but once again it comes down to simple science. Stray voltage is when we have neutral current flowing through the Earth. It’s effectively a version of ground potential rise. As such the distance spanned gives rise to higher voltages. So a cow gets a much more severe shock than I do, especially if I am standing next to her in rubber boots! But this is a far cry different from EMF that travels without direct contact.

So getting back to your statement about EMFs causing a gauss meter to jump. If you recall the original Marconi radio was a spark gap. Electrical arcs are pretty much pure white noise pulses. The rate of rise, dv/dt is pretty easily related directly to the frequency spectrum. However pulses have a cosine roll off and pulsed harmonics, not a continuous wave. So over the range of human susceptibility, roughly 15 MHz+, either the pulse is mostly below that frequency or very low power. High frequency pulses do not travel well in house wiring because the bandwidth has significant toll off above about 10-100 Khz at best. I have seen some HF arcing up into a few MHz in a 3 phase small motor due to what amounts to capacitive discharge caused by excessive dv/dt in a crappy VFD application eating up bearings but that’s as high as you ever get in a power system for extended periods and that’s not a residential scenario. So while I agree it is possible, exposure is very limited except for long exposure times.

Then we get into the exposure time issue. Except for intentional arcs (contacts and some types of surge arresters and discharge lighting), electrical arcs quickly erode away equipment. Testing for arc flash purposes at Kinetrics that does most of the testing sustained an arc at 130 VDC with a 1/4” gap for 0.08 seconds at 20 kA before it self extinguished. That’s a high energy power src, on the order of what you need to generate substantial EMF from an arc, but it’s simply not sustainable. In fact arcs are not sustaining under around 200 V and self sustaining only in special circumstances from 200-300 V. Nothing new here. Marcia Eblen from Duke has published this data via EPRI and IEEE. So the conditions necessary for constant EMF in household wiring don’t exist.

My sister in laws sister claims her kids are affected by EMF fields and that she is too. She has done substantial things to try to stop the waves and rubs around totally out of her mind because of gauss meter readings. The scientific nonsense that she utters plus all her crazy Twitter friends is clear evidence of psychiatric problems. She is into that, too, plus she has a literal tree growing up through the middle of her house. Fortunately I guess she has a good paying job so she can afford her fantasies. I blew her mind when I installed a system in her house that had copper wires connecting an LED light that generated no measurable readings on her gauss meter. I’ll leave it to you to ponder how I managed to power a diode without using AC power.

So excuse me if I don’t entertain these utter nonsense claims by the tin hat society.

So if I’m wrong, show me peer reviewed scientific studies showing substantive biological danger from ELF frequencies of EMF. I don’t care what your microwave oven test does because the wavelengths are completely wrong. I also don’t care what your gauss meter readings are because those things capture everything from 0 to a couple Gigahertz. So unless you are using a capacitor to block everything below a 3 dB point of about 100 MHz or so, your readings are garbage and do not accurately reflect human anatomy. And if you do, you’ll find you no longer read much of anything at all. Now since most of these things are nothing but wide band amplifiers hooked to a stubby broadband antenna, the readings are pretty much garbage in, garbage out.

Just trying to inject scientific reason and logic into what normally amounts to a whole lot of speculation, pseudo-science, and paranoid delusions.

Excuse me while I go run off a couple little green men that seem to have stumbled into my back yard. They are either trying to make crop circles or they are after my cows.
 

paulengr

Senior Member
The field from a long straight wire falls off as 1/r, where r is the perpendicular distance from the wire.
The field from two long straight wires separated by distance a and carrying equal and opposite current, on the other hand, falls off more rapidly. I think it is proportional to 1/(r/a)2 when r is large compared to a.
(I have had a lot of difficulty confirming that inverse square dependence. Does anyone have an authoritative source?)
So the balanced currents need to be carried in wires that follow as closely as possible the same path.

An “unbalanced” system as you call it becomes a large inductor with 1 turn. Within the loop antenna we get some coupling and close to the wire we can get capacitive coupling. There isn’t a second circuit so it’s not inductive. Capacitance is proportional to the area of the conductors and inversely proportional to the separation distance. In shielded cables it’s picofarads. It is highly noticeable in resistance grounded medium voltage systems as several Amps but the effect is proportional to the square of voltage so it’s not noticeable at 120/240. So if you are even a couple inches away unless you are using a gauss meter good luck measuring it. Loop antennas can generate or pick up RFI if they are “tuned” to the right frequency, which is into the Kilohertz or higher at the dimensions you are concerned with.

Again taking readings with a broadband RFI meter and somehow equating it to ELF frequencies is like taking crop circles seriously.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220628-2020 EDT

paulengr:

I started this thread on magnetic field intensity. I made no comment in the original post about a purpose of the thread, biological or otherwise.

Thoughout my life I have been inquisitive about things. I have tried to detect signals at low levels for roughly 80 years, and I have been involved in experiments on signal detectability, and built equipment for these tests, some 70 years ago.

So I may or may not have a purpose in making low level measurements, but I may have an interest.

You may be only interested in biological effects. Thats OK, but does not cover all aspects of magnetic fields.

If I have a long straight wire with a current flowing in that wire, then there is a magnetic field about that wire. The same for a loop of wire.

With my present sensing components I get what appear to be magnetic signals that produce about up to 10 to 20 microvolts on my meter in areas with hopefully little power line interference. With a shorted meter I have meter noise of 0 to 10 microvolts range.


ptonspary:

F. W Bell has Hall effect probes that can get down to low flux levels, but those with the greatest sensitivity are special in that they use a form of magnetic multiplication ( magnetic field multipliers ). Your probe probably is not one with the greatest sensitivity. Hall devices are fairly noisy.

Also you are probably not using bandpass filtering at 60 Hz. Thus, a fair amount of non 60 Hz signals may be adding to your background noise.

If you go somewhere in your farm open land area I would expect you to see a substantial reading from the transducer noise.

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ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Gar,
I took my 87 and 43B to middle of the section.. not quite 1/2 mile in all directions to nearest power of any kind. The 87 essentially gave me the same readings as in the home. Zeroed or not. The battery died on the 43 before I got much for comparison. I have to be within inches of wires to get reading's of any kind.
No way is it useful 1/2 mile away.
 
Last edited:

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220629-2018 EDT

ptonsparky:

I have a raw unpackaged Hall device, possibly 40 years old. No added magnetic circuit. Exciting this with 5 VDC I have a residual AC output voltage around 3 to 4 mV. This is basically device random noise. But I have not looked at it on a scope. I have no AC filtering on this other than the high pass input filter of a Fluke 27. The 3 db point of the Fluke is I believe somewhere below 10 Hz.

With my 1.5 A test AC current I have to be within several inches of the current carrying wire to start to see a signal different than the noise level of the Hall device. This is very much less sensitive to a low level AC magnetic field than is my 5000 turn coil. I could probably see a lower sensing level from the Hall device if I added a 60 Hz bandpass filter to its output to reduce some of the noise.

F. W. Bell makes some probes with what I will call magnetic amplification. This a a magnetic core that collects magnetic flux lines and concentrates these into a smaller area where the Hall device is located. This way they claim to get into the fractional milligauss range.


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