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What do you think of earth NMR? We use a proton mag to measure the frequency of H in water. The earths field strength is the reference for the measurement. Just a thought. All frequencies fall in the audio range. Whats do you think.
Tim
Tim
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Bringing metal detectors into the world of imaging!
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What is your goal Tim? To find forgotten ancient GhostTown in water?Originally posted by Tim Williams View PostGlobal capital is ruining your life?
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No I wanted to see how long it would take for someone to post a stupid response.Bringing metal detectors into the world of imaging!
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No one can give you smart response on stupid question.Originally posted by Tim Williams View PostGlobal capital is ruining your life?
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If you don't know anything about earth NMR then don't post.Bringing metal detectors into the world of imaging!
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I was posting to you for mercy and charity, not for Earth NMR, so don't be rude.Originally posted by Tim Williams View PostGlobal capital is ruining your life?
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I'm sorry WM6. I just asked a question on earth NMR. You asked me if I was looking for treasure in water. The problem is because I use LRL's for some reason that makes me target for attack. There are people on this forum I respect and seek thirr opinion on this subject not smart remarks and personal attacks. If I took your post the wrong way I'm sorry.Bringing metal detectors into the world of imaging!
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No problem Tim.Originally posted by Tim Williams View Post
I hope someone with knowleadge on matter will give you proper reply.
How do you get frequencies that fall in audio range?
I think that your measuring problem is that your reference (earth magnetic field strenght) is not constant but little changeable during day. This can be key problem of used NMR because the resonance frequency of a particular substance is directly proportional to the strength of the applied magnetic field.Global capital is ruining your life?
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Hi Tim,
There are several issues with EFNMR. Consider first the proton mag, which is a practical application of EFNMR. The element used for precession is hydrogen. Why? Because it is easy to precess (is readily polarized) and offers a decent precession signal level for detection. But you still need to put the hydrogen sample (water, or a hydrocarbon) INSIDE a big coil, pulse it with a very strong polarization field, and then listen to it with a very sensitive and low-noise receiver.
What can you do with this? Basically, all you can do is detect variations in the Earth field. Due to what? In a local sense, iron targets which cause variations in the Earth field. In a very large sense, you can map Earth field gradients caused by mineral deposits.
What you can't do is use it to directly detect, say, gold or silver. Neither of these have any effect on Earth field strength. It is feasible that a buried treasure could have an EFNMR signature due to the disturbed soil, similar to what your Geo-logger could pick up on.
Is it possible to use NMR, in some fashion, to detect e.g. gold? OK, let's assume that we can do something similar to a proton mag. We could place a gold sample INSIDE a big coil, pulse it with a very strong polarization field, and then listen to it with a very sensitive and low-noise receiver. Theoretically, the gold should precess at about 37Hz. But what you would likely find is no response. Gold has a NMR receptivity that is over 45dB below that of hydrogen, and the SNR for a proton mag is well below 45dB. So the precession signal for gold will be well below the noise floor.
All that has been discussed is for target samples placed INSIDE a big coil. As you slide the target out of the coil, both the excitation precession and the received signal will quickly drop to zero. That is, when the target is removed from the coil, everything stops working.
It's fun to think that there is a possibility we can transmit a signal and cause a target to "ring" at some characteristic frequency. And proton mags actually do this. But only at distances of 1 inch or so. Medical NMR, with its kilowatt-level excitation coil, can detect at distances up to a foot or so. Can we make a handheld EFNMR locator that detects buried gold a mile away? 100 feet away? 1 foot away? Sorry, ain't happening.
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Tim,Originally posted by Tim Williams View Post
Earth Field NMR is used primarily as a teaching tool and in some field applications. However, the SNR is pretty poor and often required a boost field to create an initial spin alignment and thereby improve the SNR.
Having said that, the sample signals are quite small and require that the sample be almost totally surrounded by the sense coil to extract enough signal from the sample to make it suitable for amplification with reasonable SNR.
It is not obvious that the NMR signals involved, or the required boost field can be extrapolated to distances typically involved in dowsing or LRLs and certainly not with a hand held, battery operated device.
HH Rudy,
MXT, HeadHunter Wader
Do or do not. There is no try.
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I agree I was reading up on EFNMR and found it interesting in that it was possible to use the earths field in that way. Just though I would get some opinions on this subject. I find it funny that some of the frequencies are very close to ones I use myself. Thanks for the input.
TimBringing metal detectors into the world of imaging!
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Hi Tim,Originally posted by Tim Williams
Just out of curiosity, if we suppose the earth's field is strong enough to impart a weak precession signal in some material, it would seem the field must be quickly removed in order to measure the precession signal. However, the earth's field fluctuations are very small percentage-wise when measured over short durations that might approach a pulse interval. Because the earth's field is weak to begin with, and because it does not pulse in any large swings of field strength, we can't expect it to cause a measurable signal anywhere near the noise floor.
Let's suppose the coil on a proton precession magnetometer was connected to a circuit that was calibrated to generate a magnetic field that follows the changes in the earth's field over the course of a day, it would seem there would be no signal measurable any time during the day in that proton magnetometer.
Yet we are talking about precession frequencies very close to the ones you use being caused by the earth's field. Am I understanding wrong? Or are we talking about the earth's field causing precession in many elements all over the landscape?
Best wishes,
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J_p for those who dowse like samples give an indication. Also using a generator a sample will cause an indication at different frequencies. I've been doing this sense 1985 and have found different things at different frequencies. Here the earths field changes from day to day not much very little. What I am saying is many of the frequencies are the same or 2hz off from what I fine using ring theory. measuring the radius of the ring around a sample. So from what my data shows for some samples I am very close to EFNMR frequencies using a device to find frequencies for samples. I'm not here to start a debate, just posing a question to those that may know this field of EFNMR. Thanks for all who answered.
TimBringing metal detectors into the world of imaging!
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Ok, then without starting a debate, what you are saying is not that the earth field is causing precession in the elements scattered across the landscape.Originally posted by Tim Williams
As I understand it you are saying is you can set up a signal generator adjusted close to the frequencies that the elements would precess in a strong enough magnetic field. And when sending (broadcasting) this signal to a field where you dowse, you find a dowsing response for different materials which correspond to a precession frequency the signal generator is set to (if the material is present in the field where the signal generator is set up). Is this correct?
Or maybe you were saying the signal generator set near a material's precession frequency could be substituted for the material, and would cause a dowsing response the same as if the material were present?
Best wishes,
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