Hi!

I need an instrumentation amplifier-circuit (INA) for scientific precision measurements of weak EMF-signals.

My input will come from 2 coils that will pick up weak EMF signals in an environment with possibly a lot of noise. So one of the coils will pick up the wanted signal + the noise and the other will only pick up the noise. That’s why I want to subtract signal no. 2 (the reference coil) from signal no. 1 (the signal coil).
My immediate plan is to use ordinary telephone pick-up coils. I have bought 2 Monacor coils that supposedly have an impedance of about 1 kOhm and a resistance about 280 Ohm.
The output of the INA will serve as input to a sound card (external, connected to a PC by USB). The AD-converter in the sound card can actually sample the signal with a sampling rate of 384000 Hz, so I would like the INA to be able to operate up to at least 200 KHz.
The external sound card is also a mixer, with 2 amplifier steps with adjustable gain, but it would be good for my signal, if the INA also has a significant gain.

I also need to build a power supply for the INA. The general power lines here in Denmark are 230V 50Hz.

So which INAs would serve my purpose?
And how should I build a power supply that doesn’t add noise or other distortion to my weak signals?
I look forward to hear from you. Thank you.

Best regards,
Henrik R.

 

For starters, your coils will only sense magnetic fields. And if the noise fields are magnetic, why not just put the coils in series, to immediately cancel the noise. That scheme works very well for guitar pickups and many dynamic microphones. The added advantage is not needing to adjust the amplifier system for good noise rejection.

 

Hi!
Thank you for your reply!
I didn't realize that 2 coils in series cancel the noise that is induced in both of them - the 'common mode' signal. I have searched for information on this, but only found information where the 2 coils have a common iron core or such. But my 2 coils will be physically separate from each other. Actually I think I will put them in 2 separate Faraday cages to further reduce background noise. Can they still cancel out the common mode signal - the noise which is present in both Faraday cages?
And in that case: Do you have another suggestion for an amplification (and impedance conversion?) to create an "audio" signal as input for my external sound card?

 

The second coil needs to be connected so that the noise cancels, so the polarity of the connection matters a whole lot. This means that you might need to reverse the connections of one coil.
Hum cancelling is a very big deal for electric guitars used onstage in some venues. Avoid using magnetic materials in your electrostatic field shields. And beware that they may tend to cancel out some of the magnetic fields that you hope to sense, because the changing magnetic flux passing thru a conductor can generate a current, meaning that it is losing energy doing that.

 

Excellent! That will make things a lot easier. Thank you!
Do you have a suggestion for an amplification (and impedance conversion?) to 'convert' the quite weak signal from my 2 coils in series, each 1 kOhm impedance, 280 Ohm resistance, to create an "audio" signal as Line or Microphone input for my external sound card? That would be much appreciated. Note: My external sound card and mixer has a 20V phantom power supply for microphones.

 

The phantom power source should be plenty for a low level amplifier used with the magnetic pickups. But certainly it should not be applied to either the coils or a dynamic microphone. Is there a way to switch off that phantom power? Many sound cards are set up for use with an electret microphone, which is a higher output low impedance source. That is unfortunate for those who try to use a dynamic microphone without realizing that power is present.
What is the input connection to your sound card? usually it is a 3.5mm stereo (TRS) plug. But it might be an XLR connector.

 

The phantom power is only when connection an XLR cable.
The possible inputs to the sound card are described as:
1 x Mic, mono: 0.5 mV (with or without the phantom power)
1 x Line In, stereo: 2 mV, 150 mV, RCA L/R
1 x Tape In, stereo: 420 mV, RCA L/R

Maybe the Mic input is sensitive enough for the weak signals from my 2 coils.
I might start trying with that.
In that case I only need to experiment with the 2 ways the 2 pick-up coils can be connected in series?!

 

One arrangement will be much less noise pickup. Worst case you may need an amplifier with a gain of 100. For 200 KHz and G=100 you need a Gain Bandwith product of 100 x 200,000=20000000 That may require two stages.

 

Great. I will just start with the 2 coils in series as Mic input for the sound card.

 

If the signal you are interested in is not strong enough, then you can use an instrument amp IC The reason being is that they usually have better common mode rejection, and any electrostatic noise picked up is most likely to appear as common mode noise.
I am wondering what sort of magnetic signals you are seeking to detect. That is rather an unusual area of exploration.

 

I want to experiment with Water Memory.
If you look at the documentary on Youtube: "Water Memory (2014 Documentary about Nobel Prize laureate Luc Montagnier) -

- then you can see that they use a simple telephone pick-up coil to pick up the EMF (or magnetic) signature of water... That's what I want to investigate.
Addition: If I have 2 coils, to cancel out the common noise, then it seems I am already more advanced than this nobel prize laureate...

 

If the signal you are interested in is not strong enough, then you can use an instrument amp IC The reason being is that they usually have better common mode rejection, and any electrostatic noise picked up is most likely to appear as common mode noise.

OK... I have experimented with 2 coils in series, and switching the polarity of one of them. The polarity makes a difference, but there is still a lot of noise(!) - also the 50 Hz hum. Putting both coils (and the water they are measuring) in aluminum foils actually makes it worse. So I need an instrumentation amp IC or the like, to amplify the signal before it enters the Mic-input of the sound card. But which?
Note, that in practice the sound card cuts off any signal over 24KHz (even when I sample with 384KHz), so for practical purposes I guess I will use 96KHz sampling.
(Remember that the sound card has a 20V phantom power. Maybe that could supply the instrumentation amp?)
I look forward to hear from you.

 

Noise cancellation depends on the coil orientation. with microphones the second coil is very close, likewise on guitar pickups. The noise in your application may even be coming from multiple sources in different directions.

 

Noise cancellation depends on the coil orientation. with microphones the second coil is very close, likewise on guitar pickups.

Do you know where I can find sufficient information on this?

The noise in your application may even be coming from multiple sources in different directions.

Yes. And a lot of it may come from the sound card / mixer itself, if it's not designed for very weak signals.

I might use a configuration of 4 coils, where a set of 2 coils physically close to each other cancel 'local' noise around them, and where the 2 sets are physically relatively far from each other. One set would record 'signal + noise' and the other set just 'noise', and then I would connect the 2 sets to the 2 inputs of an instrumentation amp IC?
Does that sound smart?
And in that case: Which instrumentation amp should I use?

 

I want to experiment with Water Memory.

Memory of water - pseudoscience.
https://en.wikipedia.org/wiki/Water_memory

"[Benveniste's] latest theory, and the cause of the current flap, is that the "memory" of water in a homeopathic solution has an electromagnetic "signature." This signature, he says, can be captured by a copper coil, digitized and transmitted by wire—or, for extra flourish, over the Internet—to a container of ordinary water, converting it to a homeopathic solution.[/QUOTE]
The APS accepted the challenge and offered to cover the costs of the test. When he heard of this, Randi offered to throw in the long-standing $1 million prize for any positive demonstration of the paranormal, to which Benveniste replied: "Fine to us."[25] In his DigiBio NewsLetter. Randi later noted that Benveniste and Josephson did not follow up on their challenge, mocking their silence on the topic as if they were missing persons.[26]

An independent test of the 2000 remote-transmission experiment was carried out in the US by a team funded by the United States Department of Defense. Using the same experimental devices and setup as the Benveniste team, they failed to find any effect when running the experiment. Several "positive" results were noted, but only when a particular one of Benveniste's researchers was running the equipment. "We did not observe systematic influences such as pipetting differences, contamination, or violations in blinding or randomization that would explain these effects from the Benveniste investigator. However, our observations do not exclude these possibilities.""

I would like the INA to be able to operate up to at least 200 KHz.

The lowest frequency of the water molecule oscillation is 22.235 GHz

 

Memory of water - pseudoscience.
https://en.wikipedia.org/wiki/Water_memory

"[Benveniste's] latest theory

I am referring to the research of Nobel Prize Laureate Luc Montagnier, done 20 years after Benveniste, which confirms Benveniste's observations.
Please don't disturb the discussion of instrumentation amps, coils, sound cards and such.

 

For an instrument amplifier with adequate frequency response visit "Analog Devices" company. They make IAs that work up to a few megahertz.
And good luck magnetizing water.

 

Please don't disturb the discussion of instrumentation amps, coils, sound cards and such.

It is about instrumentation amps, coils, sound cards, which should be able to work
with frequencies from 22.235 GHz to much, much higher.
Object, which is able emitting at 200 kHz frequency should to have dimension 750 meters,
at 20 kHz - 7500 meters, at 2 kHz - 75 kilometers and so...
Of course water can not contains such big associations of H2O molecules, therefore
water does not emit electromagnetic waves on such frequencies.

I am referring to the research of Nobel Prize Laureate Luc Montagnier, done 20 years after Benveniste, which confirms Benveniste's observations.

Full text see at https://sciencebasedmedicine.org/luc-montagnier-and-the-nobel-disease/

The Nobel Disease strikes Luc Montagnier
Luc Montagnier shared the Nobel Prize in 2008 for his discovery of the human immunodeficiency with Harald zur Hausen, who discovered the link between the human papilloma virus and cervical cancer, an event that Steve Novella took note of when Montagnier received the award. Then, earlier this summer, Montagnier appeared to endorse homeopathy:

French virologist Luc Montagnier stunned his colleagues at a prestigious international conference when he presented a new method for detecting viral infections that bore close parallels to the basic tenets of homeopathy.
Although fellow Nobel prize winners — who view homeopathy as quackery — were left openly shaking their heads, Montagnier’s comments were rapidly embraced by homeopaths eager for greater credibility.
Montagnier told the conference last week that solutions containing the DNA of pathogenic bacteria and viruses, including HIV, “could emit low frequency radio waves” that induced surrounding water molecules to become arranged into “nanostructures”. These water molecules, he said, could also emit radio waves
He suggested water could retain such properties even after the original solutions were massively diluted, to the point where the original DNA had effectively vanished. In this way, he suggested, water could retain the “memory” of substances with which it had been in contact — and doctors could use the emissions to detect disease.

BTW,
you going to make device, to receive extra energy, emitted by water in radio range.
That is, you are going to fabricate over-unity device?

 

To reduce or eliminate the magnetic noise pickup, magnetic shielding needs to be added, as well as shielding against external electrical fields. The intended signals to be captured are very low level.

 

Hi Mr. Danko,
Sorry, I am not asking about this thread. I could not contact you personally so I am posting here...Hope you will not mind.
I have recently posted one question: "I cannot change a 90 MHZ superregen receiver to 16 MHz." I achieved quenching successfully but now when I connect the amp stage, the quenching stops. Could you help kindly. Can you tell me which things are wrong like you described earlier in forum?
Please check my recent post in my profile. Thank you