50/60 Hz passive detecting system
50/60 Hz passive detecting system
(OP)
We are trying to develop an economic portable system to detect ELF magnetic fields. We would like this device be able to detect fields as low as 5 to 10 mG and if possible we would like to avoid active components to amplify the signal, because this system is addressed to people that are terrified by magnetic fields.
We have made an antenna with 200 loops, that gives 5 mV AC for a 10 mG field. The question is: which is the best way of alerting someone with such a low power signal? Even ammeters needles would move too little to show 5 mV. LED's require minimum 2 V and 20 mAmps. Any idea? Would a step up transformer work? Thank you.
We have made an antenna with 200 loops, that gives 5 mV AC for a 10 mG field. The question is: which is the best way of alerting someone with such a low power signal? Even ammeters needles would move too little to show 5 mV. LED's require minimum 2 V and 20 mAmps. Any idea? Would a step up transformer work? Thank you.





RE: 50/60 Hz passive detecting system
Supporting such superstition isn't an engineer's task.
Making money out of it is shameful.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 50/60 Hz passive detecting system
TTFN
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RE: 50/60 Hz passive detecting system
htt
or this:
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The first one is way more sensitive, and may be in higher demand for those who are particularly paranoid. You wouldn't be able to make coil-based system small enough; it'll be so noticeable that they might as well wear their tinfoil hats in public...
TTFN
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RE: 50/60 Hz passive detecting system
Gunnar, I know we live in an environment that is completely full of waves, and we live without so many problems, but some people say the can 'feel' the fields. What should we do? Help them in feeling more protected or just leave them with no help?
This is s link to the WHO EMF program. http://www.who.int/peh-emf/en/
IRstuff. Thank you for your links, but from a first look I have the impression that those sensors are for static field (Earth's magnetic field) and not for variable fields, like the one generated by 50 Hz.
Riccardo
RE: 50/60 Hz passive detecting system
I am strongly against that.
BTW, a 200 turns loop is just moot. It does work if you use a low power opamp. But if you are afraid of the magnetic fields created by the current consumption (ten - twenty microamps) then you need many more turns. What about a few thousand turns and a large area loop. That will produce enough power to light a red (red needs the least voltage) high efficiency LED. But the current in such an LED will be in the mA order of magnitude. That's a lot more "dangerous" than the 20 microamps that an opamp needs.
One question: Are you an electrical engineer? Or are you dabbling outside your field of expertise? Please read the site rules.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 50/60 Hz passive detecting system
I have been considering your project, and my feelings rhyme with "spoondoggle." If you can't just throw together some diodes to make a full-wave rectifier, then I'm inclined to tell the client "look, there are no electronics that exist that demonstrate the 'issue' without making it worse. I look forward to reading your manifesto in the paper."
RE: 50/60 Hz passive detecting system
You addressing whom?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 50/60 Hz passive detecting system
The devices have bandwidths of 10 kHz, and are more than capable of sensing a 50Hz field. The processor that you'd need for processing the data can threshold and filter the data to look for anything you want.
You have a similar problem with the wire loop, as there is no discrimination in the wire loop for any specific frequency, so if there are high-frequency AC sources nearby, it'll detect them also.
TTFN
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RE: 50/60 Hz passive detecting system
That was directed to rmarchesi.
RE: 50/60 Hz passive detecting system
RE: 50/60 Hz passive detecting system
Investigations made by national and medical research institutes in most civilized countries have shown that ELF magnetic fields have no effect whatsoever on animals or humans.
But, it is a free world (mostly) and there are lots of people that THINK that they are sensitive to magnetic fields and are eager to tell the world about their problems.
In on hospital in Sweden, a whole building was shielded because a group of patients demanded it and the doctor was too busy to find out if there was any scientific reason for it. I guess that that happens all over the world - but that doesn't mean that the 'problem' exists outside certain individual's brains.
My first studies on this 'problem' are from 1986. For 24 years, no evidence - other than different persons subjective feeling - has been presented. Au contraire, every serious and well documented study has falsified the theory about ELF magnetic fields in the gauss or millitesla range having any effect on humans or animals.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 50/60 Hz passive detecting system
Since these are ostensibly few in number and may not be fully aware of their abilities, studies of any kind would no doubt result in inclusive answers.
Regardless, we as engineers often are required by our contract commitments to design and build things of dubious value, so why not magnetic field sensors?
TTFN
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