Detector improvements

[Nenad]

I was just curious if reducing the coil cable length would increase performance.
Also, does removing discrimination circuitry help out power?
Thanks

[Rick S]

Re: Detector improvements

Nenad,
I wouldn't mess with the coil cable length because the detector design has taken this capacitance, and resistance into consideration in making the circuit. Trial and error would be my best answer to the discrimination circuit. You know working with metal detector circuits and trying to get info from the ones on the market is like asking someone you don't know to give you a million dollars. They have patents on everything and I don't know why info isn't given out more freely. That is why all the tech heads on metal detectors curse forums like this one. My computer just went through a crash. It is up and running again. I will be watching.... Rick S

[Carl]

Re: Detector improvements

Nenad,

I agree with Rick, cable capacitance is part of the operating equation. Even if it were not, it is pretty insignificant in terms of transmit energy loss.

The disc. circuitry does not affect transmit power but it does affect receiver sensitivity. You will get the greatest depth with a raw all-metal mode... the filters used in the discriminator reduce depth slightly. How much depends on the filter design.

As Rick said, getting circuit info is tough, and there is absolutely no reason why it should be so. All of the manufacturers know what the competition has, so why withhold it from the customer? Anyway, of all the manufacturers White's appears to be the most open, and will send schematics on older models.

- Carl

[Reg]

Re: Detector improvements

Cable length doesn't have much effect on overall performance. In fact, some manufacturers used to make extensions before they lengthened their cables.

Depth increases can be obtained by knowing all the little quirks of the detector you are using and then using those to your advantage. Manufacturers change their designs so what works for one model might not work for another, or not work for a different machine.

Example: Ground balance is critical for maximum depth, especially in bad ground. It is also not designed the same from brand to brand or even model to model in some cases. Unfortunately, most people do not really understand ground balance (gb) so many of the manufacturers cheated and either installed an internal preset gb that works with the disc mode, or introduced a phase shift so the disc mode is positively balanced. The reason? People were complaining about false signals from rocks. This basically cured the "hotrock" problem.

Specific example: part of the "Super Tuning" technique of the tesoro's would compensate for their internal gb offset.

[Reg]

Re: Detector improvements

Nenad,

Rick and Carl are right, getting information is tough. As Carl said, White's did sell schematics for several of their models as did Fisher. I don't know if they still do, but that is a good place to start to learn more about detectors in general. Also, the Fisher filter design is somewhat similar to Tesoro's, and the older Whites were very similar to the old Technetic designs.

Several of the patents, especially those produced in the 1980's were pretty detailed on how detectors worked as well as circuitry. Good ones to look for are by Payne, Hirschi, Johnson, Lahr, and for a really old design, Alan Hametta. (the last one may not be spelled right). They can be viewed at the Delphion website by typing in metal detector in the search box at the Delphion site.
Reg

[Carl]

Re: Detector improvements

I also have most of the patents right here on this web site. Click below.



Patents

[Mark Pauls]

Re: Detector improvements

Hi Nenad

Take care!
I ones tried to change the cable on a Whites coil to the same lenght and cable dimensions that was equal. It did not work at all!. All metal was detected as Iron.

So I agree with Rick there is more into it than just cutting the cable.

Mark

[Nenad]

Hey guys

Well I won't be touching the cable length.
I'll be attempting a coil fix soon, but I'm still having problem at the plug end.
When I just touch it slightly in sounds off as if it's losing contact.
Thanks for the replies, Nenad

[Reg]

Re: Detector improvements

Sorry Carl,

I didn't know you had the patents listed on this site. I reviewed some of them and I believe patent 4677,384 (Technetics) was their patent for the design of Big Bud Pro (when they owned Bounty Hunter).

[Reg]

Re: Hey guys

Sorry if I upset anybody with my statement about cable length, but one has to remember that most VLF's operate in the 6000 to 20,000 hz range. The wavelength of such frequencies is 60,000 to 160,000 feet or more so cutting off a couple of inches shouldn't make a difference. Also, the signal is a sinewave.

Digital signals like in computers are more critical where rise and fall times are important. Also, the harmonics are great in a digital signal so wire length is critical.

The point I was trying to make is shortening the wire on a coil shouldn't cause major problems. If a problem exists, like the one of moving the cable causes noise, I would cut it off and resolder it back on. I have in the past several times with no problems on different detectors.

However, it is possible the problem lies in the plug itself. If it has been taken off alot, it could be expanded and not making up right. Most of the plugs use a female tubular connector that can expand. I have taken a small pick and bent the pins sides closer together as a temporary fix.

One last note, on a few detectors, the plug on the control unit is soldered directly on the pc board. It is possible for one of the connections on the board to be the problem.

Again, sorry if I upset anybody.

Reg

[Sean Goddard]

Re: Detector improvements

The fact that some designs mirrored others, just goes to show who used to work for whom.