Clarification of terminology? Reference red clay discussion

[Anonymous]

In reference to a discusssion on this forum about penetrating red clay, etc., one poster was wondering how well the Minelab Explorer and other multifrequency detectors would do for nuggets. He refered to them as vlf detectors.
Its my understanding (and confirmed wirh George Payne) that the Explorer and Sov are not vlf detectors. They are pulse. They transmit a square wave and then process the harmonic returns.
Two other multifreq units:
The fisher CZ series transmits a distorted sine wave and use a harmonic of the primary freq as thier second freq. So this second freq would be of less energy.
The Whites DFX transmits two sine waves of equal amplitude, which I would think would be better. I plan on trying the DFX with the new DD coil in bad ground an see how it does.

 

[Anonymous]

I know who George is, and I

 

[Anonymous]

No need to take it personally. I work with George Payne

 

[Anonymous]

They are Broad Band Spectrum technology as they call it using 1.5hz-100Khz with full discriminating capabilities. Call it what you want, but it is not Pulse!!!!

 

[Anonymous]

HI Frank and all
Sorry Frank but you are mistaken in thinking that the Soverign and Explorer are pulse units. They are a BBS system which is Minelab talk for Broad Band Spectrum. They work on multiple frequencies but they are still a VLF machine, they require a balanced coil such as a DD to work and have some interesting circuitry contained in the search coil. I have seen inside one of their coils and can speak from experience. IF you like I can ring Minelab and confirm that they are indeed VLF detectors.
Cheers
Steve D

 

[Anonymous]

"Discriminating Time Domain Conducting Metal Detector Utilizing Multi-Period Rectangular Transmitted PULSES.
From Summary of invention:
"The subject of this invention is a PULSED, discriminating, time domain conducting metal detection apparatus utilising rectangular transmitted PULSES.
Goes on to talk about the use of a recieve coil and syncronous modulation, etc etc.
George Payne designed the Hot coil for the Sovereign and has looked at the waveforms of that unit. He called it a pulse. You can call it BBS or whatever marketing term you want to use but it still a square wave.

 

[Anonymous]

Is this a patent for the SD2200d which has a form of discrimination and is a pulse induction machine?Check the date of the patent as the soverign was introduced about 1990-1991 .

 

[Anonymous]

I have those patents as well.

 

[Anonymous]

Hi again Frank
The reason for the square wave pulse is to transmit on all frequencies. A square wave consists of many frequencies and harmonics. To construct a multiple frequency detector using pure sine waves would be a constructors worst nightmare. Also Minelab is noted for its bull as regards its patent applications. They dont want to make it easy for anyone to understand how their detectors work.
Cheers
Steve D

 

[Anonymous]

Yes thats correct. The higher freq harmonics would be of a lower amplitude compared to the fundamental. To me that means it would reduce its effectivness to lower conductive items such as gold, nickel, etc. I'm not saying the Explorer is not a good unit. I only wanted to point out it not truly transmitting individual sine waves at 28 frequencies. I thought this was an educational, and sometimes technical forum.

 

[Anonymous]

Hi Frank and All,
I have a couple of schematics which describe themselves as

 

[Anonymous]

Hi All,
Gee, this is a really interesting topic that has certainly generated a lot of responses.
So, I guess I might as well add my two cents worth (pun intended). From what I remember from reading the patent, different period rectangular waves are transmitted, not square waves. They are not continuous waves like typical VLF's, or even like the square wave generated in the Fisher unit, Dave mentioned.
So is this a pulse unit, well yes and no. It is not a PI in the traditional sense. However, a rectangular pulse signal is generated and the received signal is analyzed. Some of the pulses are short, others are longer and there is some finite time between pulses. So, in the broadest terms, it is a quasi form of a pulse unit, just not the conventional design that coined the phrase PI. It certainly doesn't fit in the typical VLF catagory.
So, is it really a broadband unit? In my opinion for what it is worth, the term Broadband is advertising hype. It worked by the responses I have read. Will it go so much deeper? I think not. The "multi-period" pulses do not pound each other into the ground. Instead, they will disperse just like they do on other detectors. Do they have the extra energy to go deeper like a more typical PI? Again, I think not.
I don't have a copy of the patent at my disposal right now, but if it the one I am thinking of, a rectangular pulse is generated into the coil and the analysis is done analyzing the decay curve of the receive signal. This is somewhat like what is done on a PI unit as we know it.
They make test equipment called pulse generators. Heck, my spice program has one. This equipment generates a square or rectangular pulse. The BBS units generate a rectangular pulse.
Maybe we could call this thing a pulse generator type machine, rather than a PI. The term PI or pulse induction has taken on a traditional concept, just has the term VLF. Actually, the "Broadband" detectors really do not fit in either catagory if we maintain the traditional thought. Who knows, we could call it the hybrid.
Just having fun.
Reg

 

[Anonymous]

indeed an interesting subject.

 

[Anonymous]

Hi Russ,
I think the patent that covers the SD is patent number 5,576,624. This patent was also issued in 1996.
Reg

 

[Anonymous]

Hi Jan,
I am not sure how George phrased the BBS machines to Frank, but if I remember correctly, George did mention to me that the units are pulse units. I don't think he said they were PI's, but used a term like they used a pulse technology. As Frank said, George built coils to be used on these type of machines so he had to have a full knowledge of the type of operation the unit used.
In this case, it is simply an argument over terminology. George's Payne's 1978 patent used triangular current pulses to ground balance a detector and to determine ferrous from non-ferrous objects. Was his design a pulse unit? Yep. Was it a PI as we know them today? Nope.
Eric can correct me if I am wrong, but the term "pulse induction", or PI as it is commonly called, was introduced to satisfy a conflicting name problem. This term has apparently been used for this type of detector ever since. However, another fundamental design can be called a pulse unit if it uses pulse technology. It just might not fit the PI name itself.
VLF's are really T/R type detectors. They are just part of an evolution that went from operating at higher frequencies down into the VLF (Very Low Frequency) range. So, these T/R detectors are now called VLF's.
The point I am trying to make is, PI's are a pulse type detector, just as was the one designed by George Payne. The BBS units fall into the same generic catagory. Are all three, PI's? Nope, but they are pulse type units.

 

[Anonymous]

A pusle detectector measures the hysterisis of the the pulse it induces in the object it hits.
A VLF detector uses a radio wave-square wave, sine, or saw tooth. Every kind of wave has different characteristics and consists-if you want-a series of like pulses in a train.
These pulses in train form are RF and have a certain frequency.
Doesn't a PI have a certain frequency too? Yes-but analyzes NOT the same pulse it sends out unlike a VLF which analzyes the change in the same pulse it sent out.
My understanding-TOTALLY different kind of pulse each type of detector recieves back in terms of pulse it sent out.

 

[Anonymous]

Hi Cappy,
The primary difference is that induction balance/TR/VLF detectors do the receiver measurement during the transmit period (as there is no off time). PI detectors do the measurement in the period that the transmitter is well and truly off.
Eric.