EMF Detector made easy?

[Bryan]

Hello one and all.

I have been looking into building a "very" sensitive EMF detector due to
issues with power lines in the area. I am sorry to say that I have no REAL
idea on how to do it.
I was also told that there is a way to build a device that would use Hall
effect sensors to measure the earths magnetic field. It would be much more
sensitive and would work if adjustable. I have yet to find a circuit design
that will give a visual as well as audible measurement. An LED bar graph
would be ok.
Any good ideas on what I could build that would do this?

Thanks for your help.

Bryan

 

[Larry Brasfield]

Hello one and all.

Greetings, one.

I have been looking into building a "very" sensitive EMF detector due to
issues with power lines in the area. I am sorry to say that I have no REAL
idea on how to do it.

Then perhaps you have no real idea of the
potential hazard, and rely on the morass
of conflicting, often misconceived studies
as the basis for deciding there is an issue.

I was also told that there is a way to build a device that would use Hall
effect sensors to measure the earths magnetic field. It would be much more
sensitive and would work if adjustable. I have yet to find a circuit design
that will give a visual as well as audible measurement. An LED bar graph
would be ok.
Any good ideas on what I could build that would do this?

If I wanted to do that, I would probably use a
simple coil pickup, followed by a high gain semi-
narrowband 60 Hz filter in front of a PIC's or uP's
A/D input, then implement a much narrower filter
using DSP to pull what is likely to a small signal
out of the noise.

It would be easy to create any display you like
using software and one pin per LED or even
multiplex LEDs to drive more of them. For,
example, at 1 nanoTesla, the red light could
blink gently. At 1 microTesla, the bar would
be fully on and blinking omenously. At higher
levels, you could spell out "Run for you life!",

Thanks for your help.

You are welcome.

 

[Rich Grise]

Hello one and all.

I have been looking into building a "very" sensitive EMF detector due to
issues with power lines in the area. I am sorry to say that I have no REAL
idea on how to do it.
I was also told that there is a way to build a device that would use Hall
effect sensors to measure the earths magnetic field. It would be much more
sensitive and would work if adjustable. I have yet to find a circuit design
that will give a visual as well as audible measurement. An LED bar graph
would be ok.
Any good ideas on what I could build that would do this?

Thanks for your help.

I'd say that if they're too low to detect except with specialized ultra-
high sensitivity equipment, you're blowing smoke up your own ass.

Cheers!
Rich

 

[Larry Brasfield]

[System approach using uP cut.]

It would be easy to create any display you like
using software and one pin per LED or even
multiplex LEDs to drive more of them. For,
example, at 1 nanoTesla, the red light could
blink gently. At 1 microTesla, the bar would
be fully on and blinking omenously. At higher
levels, you could spell out "Run for you life!",

Just to help promote this approach ahead of
the other (as yet unseen) contenders ...

With a little extra complexity in the coil and a
few switches, it could also provide an arrow to
indicate which direction the irradiated user ought
to run. Otherwise, given the usual arrangements
in the vicinity of power lines, he might run without
gaining any *real* benefit from the effort.

 

[Bryan]

Gosh Rich, thanks for the insight!
What a pal!

 

[Robert Scott]

Google "Fluxgate magnetic"


-Robert Scott
Ypsilanti, Michigan

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Hello one and all.

I have been looking into building a "very" sensitive EMF detector due to
issues with power lines in the area. I am sorry to say that I have no REAL
idea on how to do it.
I was also told that there is a way to build a device that would use Hall
effect sensors to measure the earths magnetic field. It would be much more
sensitive and would work if adjustable. I have yet to find a circuit design
that will give a visual as well as audible measurement. An LED bar graph
would be ok.
Any good ideas on what I could build that would do this?

Thanks for your help.
Bryan

It's not difficult to build, you an use a ferrite loopstick with a lot
of fine wire wound on it as the sensing probe. One of these is here.
http://www.zen22142.zen.co.uk/Circuits/Misc/emf.htm

Here's a meter using Hall effect sensors.
http://my.execpc.com/~rhoadley/magmeter.htm
http://my.execpc.com/~rhoadley/magmetr1.htm

The big difficulty is calibrating it to a known standard. And they are
not that expensive so there is no point in building one yourself.
There are several companies that offer a calibrated EMF measurement
meter for under a hundred dollars. Here's one with LEDs for under $25.
Also the cellsensor mentioned below. http://www.lessemf.com/gauss.html
Here's their main page
http://www.lessemf.com/

Two other inexpensive meters mentioned in a paragraph from a story found
with google:
"I brought an am radio to the office and it would be very noisy in that
office but not in the other rooms and really bad near the wall and
ceiling. I then went out and bought an emf meter (cellsensor, analog
meter, single axis, $42.00) and measured very high readings only in that
office and the hallway. It would blink and beep like crazy even on the
high setting. I did much research and talked to other engineer friends
who tell me it is unconceivable to have that much emf. So I bought a
digital emf meter (A.W. Sperry EMF-200A, single axis, $60.00) and proved
it. I was getting over 199 mg at the wall about 2" from the conduit
behind sheetrock. It went off the scale about an inch from the wall."

 

[Luhan Monat]

I'd say that if they're too low to detect except with specialized ultra-
high sensitivity equipment, you're blowing smoke up your own ass.

Cheers!
Rich

Try Google: +"smoke detector" +anal

 

[Mark]

to start, think about this

do you want to measure the ELECTRIC field at 60 Hz?

or

do you want to measure the MAGNETIC field at 60 Hz?

that is two completly different measurments.

Measuring an electomagnetic field implies you are in the far field
meaning you are many wavelengths away from the source which at 60 Hz is
several miles.

Mark

 

[Bryan]

Try Google: +"smoke detector" +anal

I think I know how I am going to work this now.
Thanks to everyone for their help. Well, almost everyone. For Rich I guess
just a peice of advice.... Rich we all know that liquids conduct
electricity. So, be carfulful next time you are around power supplies, and
don't forget to wipe your chin! He will understand if he really cares.

Cheers!

 

[Rich Grise]

I think I know how I am going to work this now. Thanks to everyone for
their help. Well, almost everyone. For Rich I guess just a peice of
advice.... Rich we all know that liquids conduct electricity. So, be
carfulful next time you are around power supplies, and don't forget to
wipe your chin! He will understand if he really cares.

Well, an aluminum foil hat would be the cheapest solution.

What "issues" do you have with power lines in the area? How sensitive
does this detector have to be? I still say, if you can't detect something
it's probably not worth worrying about very much.

Thanks,
Rich

 

[John Woodgate]

to start, think about this

do you want to measure the ELECTRIC field at 60 Hz?

or

do you want to measure the MAGNETIC field at 60 Hz?

that is two completly different measurments.

Absolutely. The OP clearly understands so little about the subject that
advice on making a detector is futile.

Measuring an electomagnetic field implies you are in the far field
meaning you are many wavelengths away from the source which at 60 Hz is
several miles.

For 55 Hz, the distance is approximately 1000 km.

 

[Frithiof Andreas Jensen]

Any good ideas on what I could build that would do this?

A Proton Magnetometer for entertainment/nerd value or a Flux-Gate can
measure the magnetic field component - *what for* and *how to calibrate* is
for the user.

Maybe easiest to buy?

The Electric component can be seen in the dark when holding a flourescent
tube at one end and the other closer to the wires - The 440 kV "SuperGrid"
crossing Didcot, UK will light up the tube a fair bit.

I did the experiment after getting small chocks while carrying a
well-insulated child in a Nylon suit on my shoulders below the wires
whenever child touched my head.

Anyway - Electrometer is the word, I think.

 

[Rich Grise]

Hello one and all.

I have been looking into building a "very" sensitive EMF detector due to
issues with power lines in the area. I am sorry to say that I have no REAL
idea on how to do it.

You could check with some of the strawberry growers who are using the
whole corridor under the hi-line alongside I-605. They might know
something about the effects of power line induction.

Good Luck!
Rich

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

You could check with some of the strawberry growers who are using the
whole corridor under the hi-line alongside I-605. They might know
something about the effects of power line induction.

Good Luck!
Rich

GASP! You mean those strawberries we eat have been irradiated?!? Don't
let the organic nuts know!

People don't realize how much of an electrostatic field there is around
those high tension lines. But it rapidly dissipates after a few scores
of feet.

 

[ptaylor]

due to


no REAL



GASP! You mean those strawberries we eat have been irradiated?!? Don't
let the organic nuts know!

People don't realize how much of an electrostatic field there is around
those high tension lines. But it rapidly dissipates after a few scores
of feet.

My girlfriend and I were once driving down a road with lots of
high-tension lines above..(Going down LoLo Pass,on Mt.Hood,in Oregon,the
wires were coming from the Bonneville dam.)
And with the sun-roof open we could hear them hissing and buzzing..
We noticed after a while we felt kind of "odd"..not really dizzy
but,"wierd-headed"..
We both noticed it,and I commented to her about it,and she had noticed
it about the same time..
The lines are pretty dang low in some places,I probably could have stood
out of the sunroof,and raised my arm,and got an arc to jump to
me,they're only like 15-20 feet overhead in places!!
Wierd stuff.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

My girlfriend and I were once driving down a road with lots of
high-tension lines above..(Going down LoLo Pass,on Mt.Hood,in Oregon,the
wires were coming from the Bonneville dam.)
And with the sun-roof open we could hear them hissing and buzzing..
We noticed after a while we felt kind of "odd"..not really dizzy
but,"wierd-headed"..
We both noticed it,and I commented to her about it,and she had noticed
it about the same time..
The lines are pretty dang low in some places,I probably could have stood
out of the sunroof,and raised my arm,and got an arc to jump to
me,they're only like 15-20 feet overhead in places!!
Wierd stuff.

You were probably deceived by the lack of something to compare them to,
and they were much higher than 20 feet. There is something like 800
feet between towers, and the lines can sag somewhat, but they have to be
certain heights above ground because of the high voltages, which can be
a half million volts. The humdity in the air makes the crackling
louder, but there's always some corona discharge when the voltages are
that high.

Check this out. Click on BIG Arcs and Sparks and D/L one and view it.
http://www.teslamania.com/

 

[Mark]

why do you think it was the HT lines?

maybe you should check your car for CO

Mark

 

[ptaylor]

You were probably deceived by the lack of something to compare them to,
and they were much higher than 20 feet.

Yea,they probably were higher than 20 feet,but MAN they look LOW..
It's funny when you see the wires up close,and realise that the "little"
cables up there are like 4 inches diameter! (and there's 3 cables per
conductor/phase,connected together with Y shaped pieces.) and those long
glass insulators they're hanging from..they must be like 10 feet long!

The crackling/hissing/buzzing noises are kinda freaky.
I should go up there and take pics,or video or something..
It's a creepy place! Desolate gravel "pits" on the side of the
road,where people shoot off guns,and dump rubbish..

 

[John Woodgate]

I read in sci.electronics.design that Watson A.Name - "Watt Sun, the

You were probably deceived by the lack of something to compare them to,
and they were much higher than 20 feet.

How close do you get to the overhead cables at the train station? Very
close, in UK (3 m minimum, I believe) and they have 25 kV 50 Hz on them.