Nexus Standard SE

[Nexus]

This isn't correct. You are talking about the coupling between the two coils, I'm talking about the receive signal being shifted time wise, similar to the phase shift caused by eddy currents flowing in a metal object. This phase shift can't be duplicated by upsetting the inductance and balance with minerals that are purely magnetic (and don't also produce a resistive or loss component)..

But it is exactly the coupling between the coils that all detector circuits measure. The ground and all metals are the very cause for disturbing this very coupling.
From a normal soil the time shift in the RX is too small for any reasonable measurement. But we do measure great changes both time and amplitude wise in highly magnetic soil conditions.
Get out with e portable oscilloscope and see what happens.

[Nexus]

A relatively small sample of soft ferrite, or magnetite with similar properties, will change the coil's inductance and the coupling much more than a large copper coin ever will (at depth) but the ferrite doesn't cause a phase shift and the coin does. The ground here can produce a phase shift of up to several degrees whereas the magnetic black sands found in most parts of the world don't produce a phase shift.

Buddy you really have to verify your watch.
Every ferrite, all of them and all black sand cause significant phase shift.
I can demonstrate this any time and any day on a video.
Phase shift is caused by every material that exhibits either some conductivity and/or magnetic properties.
Conductivity causes phase shift because of occurring Eddy currents this is the so called active component.
Magnetic properties (also known as paramagnetism) cause phase shift due to influence over the inductance of winding loops and also by strongly shifting the coupling between loops - the so called reactive component that is at it's peak when coils are very close to the ground surface.

[Nexus]

A piece of soft ferrite is sometimes used to null the coil. This will alter the amplitude but it won't alter the actual GB setting (phase) in a well built design. That is, if the GB is set to null a particular ground sample, then it won't need readjusting after we change the null point with the soft ferrite. If it does then there is something wrong with the design.

This is how crap detectors are manufactured. Any alien object between the loops will demolish significantly the performance of the search coil. Trust me. I know a great deal about search coils. We are the only manufacturer world wide of a fully tuned in resonance search coils. Ask your self why.

[Nexus]

The CTX3030 is definitely not a vlf and PPS is not the same as frequency. VLF measures the amplitude and phase of the received signal, nothing else.
FBS is a completely different beast as is obvious in the patents and the Minelab white paper.

The way CTX is analysing the signals have nothing to do with weather it is a VLF or not.
Some have measured the TX of the CTX to be a square wave. That of course is only when the search coil is not connected. After the search coil is connected this is no longer the case as every loop will filter out the square waves into a sine wave. The reason for use of a square wave in the FBS (full band spectrum) technology is to be able to measure certain harmonics that will not occur in sufficient amplitude if the primary TX is a sine wave.

The one fact that is most important to qualify any metal detector design is the RX loop and what is the measured output signal of that. I can assure you the CTX RX signal is a nice sine wave.

The Fisher F75 have a triangle wave oscillator that turns into a quality sine wave once the TX is connected. So what kind of detector you'll make out of that? It is still a VLF, because it operates in the very low frequency band.

[Bill512]

From this picture I can tell this SE Ultima coil was manufactured relatively recently. Since we sell very few of these coils how come we don't know about you?
If you had any problems with this detector was it not the right thing to do to contact us and discuss the GB issues? You seem to have good English, so why not call us, but come here to talk?
How many people you think in the entire world will be able to tell you what to do with this combination?

Let me be as clear as I can.
With Nexus the larger coils have much less GB problems than the small ones. This is because the larger coils in our designs are of the same Q as the small ones and use the same oscillator Voltage swing.
If you had problems with GB in this case it is entirely caused by lack of knowledge of how these big things operate. It is well explained in the User Manual, not that many bother to ever read it.

First step to getting things right is to turn the sensitivity control down. Do this and see what happens.

the detector is not mine, the owner is a friend who came, some months ago, for a test on some deep targets.
Of Course, we set the sensitivity to the lowest level ( a trivial practice in similar situations).
Also followed the instructions on page 13 , but there wasn't any real improvement.
Later ,while playing with GB and Disc to cut responses from low conductivity targets, the detector became "quieter", but with a severe loss in sensitivity (lower than a simple VLF).

[Nexus]

the detector is not mine, the owner is a friend who came, some months ago, for a test on some deep targets.
Of Course, we set the sensitivity to the lowest level ( a trivial practice in similar situations).
Also followed the instructions on page 13 , but there wasn't any real improvement.
Later ,while playing with GB and Disc to cut responses from low conductivity targets, the detector became "quieter", but with a severe loss in sensitivity (lower than a simple VLF).

If you discriminate low conductivity targets (small non-ferrous) and loose depth then either the detector is faulty or your adjustments are incorrect.
Please tell to your friend to contact me and tell me what are his problems and do not continue to report misunderstanding in here. This tread is not even related to MkII.

You and your friend are not going to be the first to say - We'v done everything possible, etc!
Because there is one thing that you have not done, before coming to talk in public.
You and/or your friend did not get in contact with us to find out what is wrong, but assumed the detector is not working as expected.

If your friend does not talk to us how can we ever be of any help?

Even now reading your post I can see that you are not asking for any assistance, but reporting problems, which I am quite sure are not any close to your description.

[WM6]

What a great detector, that author only is able to set it properly.

Why then you wrote user manual? Is it correct? What if your user manual is faulty?

Metal detectors are not rocket science and experienced detectorist should be able to set up all such devices even without user manual, not to say without special help of producer.

You say here nonsense and to offer 11 different coils for one model of detector is nonsense too.

[Bill512]

If you discriminate low conductivity targets (small non-ferrous) and loose depth then either the detector is faulty or your adjustments are incorrect.
Please tell to your friend to contact me and tell me what are his problems and do not continue to report misunderstanding in here. This tread is not even related to MkII.

You and your friend are not going to be the first to say - We'v done everything possible, etc!
Because there is one thing that you have not done, before coming to talk in public.
You and/or your friend did not get in contact with us to find out what is wrong, but assumed the detector is not working as expected.

If your friend does not talk to us how can we ever be of any help?

Even now reading your post I can see that you are not asking for any assistance, but reporting problems, which I am quite sure are not any close to your description.

my friend does not consider these failures as a big issue ,as long as he will try to avoid difficult ground ,as red clay.
As for me ,I do not want any assistance to complete a trivial task, as is to ground balance manually a VLF detector.

[crane]

But it is exactly the coupling between the coils that all detector circuits measure. The ground and all metals are the very cause for disturbing this very coupling.
From a normal soil the time shift in the RX is too small for any reasonable measurement. But we do measure great changes both time and amplitude wise in highly magnetic soil conditions.
Get out with e portable oscilloscope and see what happens.

I tell you our ground produces a large phase and amplitude shift and you tell me to measure it?????????????

You are still only talking about the apparent phase shift that occurs around the balance point either side of the null or when it flips over the null when the coil is presented to pure ferrite. If what you say is true then a given change in amplitude and/or inductance would cause the same phase shift for all soils, but it doesn't, and we would be able to duplicate a coin's amplitude and phase shift by just altering the coupling and inductance, but we can't, and note that ferrite (or magnetite) changes the inductance and RX amplitude much more than a coin at depth and yet the phase shift caused by the ferrite is tiny or non-existent compared to the coin's phase shift which is usually much further away!

With SF VLF the ground signal is comprised of two components usually referred to as X and R and one is subtracted from the other to achieve GB. It is incredibly obvious that some ground, eg, magnetic black sands, can produce a huge amplitude shift (X) and no or very little phase shift (R) whereas other ground can produce the same amplitude, or even less, plus a very large phase shift.

You can square up the RX and see the phase shift without the amplitude shift.

I think your theory needs more work!!!

[crane]

This is how crap detectors are manufactured. Any alien object between the loops will demolish significantly the performance of the search coil. Trust me. I know a great deal about search coils. We are the only manufacturer world wide of a fully tuned in resonance search coils. Ask your self why.

You completely missed the point!!! And I think you should ask why all other manufacturers stopped using resonant receive coils years ago!!!!!

Read what Dave J said here http://www.geotech1.com/forums/showt...037#post151037
and what Dave Emery said here http://www.geotech1.com/forums/showt...4956#post24956

Make sure you read both.

[crane]

The way CTX is analysing the signals have nothing to do with weather it is a VLF or not.
Some have measured the TX of the CTX to be a square wave. That of course is only when the search coil is not connected. After the search coil is connected this is no longer the case as every loop will filter out the square waves into a sine wave. The reason for use of a square wave in the FBS (full band spectrum) technology is to be able to measure certain harmonics that will not occur in sufficient amplitude if the primary TX is a sine wave.

The one fact that is most important to qualify any metal detector design is the RX loop and what is the measured output signal of that. I can assure you the CTX RX signal is a nice sine wave.

You assure me that the CTX RX, a multi period rectangular waveform, is a nice sine wave?????? You must be joking?
If this is the case then you must also believe a PI DD's RX waveform is a nice sine wave during TX?????? (It's obviously not!)
And you must also believe a PI TX frequency is the same as the pulse rate?
The ML GP PI fundamental operating frequency is approx 1300Hz but each cycle is comprised of one long and three short pulses. What is the TX frequency in this case??

The industry usually defines a VLF detector as one that transmits and receives a single or multiple frequency CW which is usually but not always a sine wave. A single frequency VLF such as the Nexus only measures the amplitude and phase of the received signal, nothing else.

The CTX is much more complex but we would need to clear up a few points first. I think this would be very difficult though after reading the "science" on the Nexus web site which states that PI detectors have an advantage over vlf because of the high voltage spike but this is obviously incorrect because removing the clamp or clamping the spike to a lower voltage has no effect on performance.

The Nexus "science" also states that a PI detects by measuring how a metal target alters the electro-magnetic properties of the loop and this is as wrong as it can possibly get!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I'm sure you will disregard most of what I say but, in order to understand and address complaints re GB, sooner or later you will have to realise that highly magnetic black sands that respond as pure X produce a high amplitude RX but only a small or no phase shift compared to ground with a high R component. It seems that you are only acquainted with the former in your part of the world.

[Gwil]

Just to get this clear, are we talking about a receive coil in a parallel or series resonant configuration? Thanks.

[Nexus]

You assure me that the CTX RX, a multi period rectangular waveform, is a nice sine wave?????? You must be joking?
If this is the case then you must also believe a PI DD's RX waveform is a nice sine wave during TX?????? (It's obviously not!)
And you must also believe a PI TX frequency is the same as the pulse rate?
The ML GP PI fundamental operating frequency is approx 1300Hz but each cycle is comprised of one long and three short pulses. What is the TX frequency in this case??

The industry usually defines a VLF detector as one that transmits and receives a single or multiple frequency CW which is usually but not always a sine wave. A single frequency VLF such as the Nexus only measures the amplitude and phase of the received signal, nothing else.

The CTX is much more complex but we would need to clear up a few points first. I think this would be very difficult though after reading the "science" on the Nexus web site which states that PI detectors have an advantage over vlf because of the high voltage spike but this is obviously incorrect because removing the clamp or clamping the spike to a lower voltage has no effect on performance.

The Nexus "science" also states that a PI detects by measuring how a metal target alters the electro-magnetic properties of the loop and this is as wrong as it can possibly get!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I'm sure you will disregard most of what I say but, in order to understand and address complaints re GB, sooner or later you will have to realise that highly magnetic black sands that respond as pure X produce a high amplitude RX but only a small or no phase shift compared to ground with a high R component. It seems that you are only acquainted with the former in your part of the world.

I manufacture detectors for 20 years. Very soon Nexus Standard MP is coming out and as a matter of fact it does outperform every other IB on mineral conditions, regardless that you chose disregard the video that I have published.

What exactly do you have to substantiate your claims? Scientific degree? Manufacturing results? Designs of any kind?

Would you like to see on a video exactly what is happening with the CTX TX and RX and when?

Your arguments will not come on top no matter how hard you try, unless you prove them in a working model.
AND THIS IS AS RIGHT AS IT CAN GET.

[Nexus]

The Nexus "science" also states that a PI detects by measuring how a metal target alters the electro-magnetic properties of the loop and this is as wrong as it can possibly get!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

What you "quote" is not written in the Nexus science page. It is only another one of your misinterpretations. Read again carefully please and do not continue to post BST after our trade mark or things will get rough for you.

The Nexus science page is written on a "street" language in a manner of speaking, not in any academic way. Simple as possible.
You don't seem to understand that, but you also misinterpret the academic expressions trying to push into the world some theories of your own.

[Nexus]

Just to get this clear, are we talking about a receive coil in a parallel or series resonant configuration? Thanks.

Neither.
It does not matter if the RX is in any resonance at all. The described above occurrences near black sand and various types of hot rocks are valid for any loop, what so ever. We have tons of measurement data.