Beach detecting detector

[urge38]

Hi Guys,

so, I only beach detect, done it for as long as I can remember, used many machines, but I can't help but notice, the multi freq metal detectors actually impair the detector on difficult ground (ground to mean conditions)
before you all jump on my, let me explain.

I am no tec guy, not meaning to say I dont know nothing about a metal detector, but I dont build them, flooring was my trade.

all I can offer is my 34 years of only beach detecting, NOW please understand, there are beaches and there are beaches.

I detect the uk beaches, my pre-furred beach can be lovely deep sand on second, and a few hundred yards away there is still yellow sand, BUT un be-known to you, under the sub yellow sand there is hell lol

every one says multi freq, and while they are good, I personally think they can add to the problem when in difficult ground conditions (again, I know its contrary, but its my feelings from years of using them)

while I do admit some muti freq are stable in difficult conditions, I think the lose a lot in depth when the going gets tough.

and that's actually my point, I see them lose depth when the going gets tough.

I recently swung a single freq machine on my beach and it was very deep in all conditions, it did lack a lot in other ways, but it hit deeper than a multi freq, it was similar to a PI not in many ways, but it was similar.

I cant repeat this enough, difficult conditions is what I am referring to.

so whats the point to my post

what is the deepest and most stable detector you have swung in DIFFICULT conditions on a wet beach

[surfdetector]

The Crossbow is the best machine that I have built and used thus far. The beaches that I detect have their share of black sand and hot rocks.

[urge38]

is your corssbow a PI or a VLF ?

[surfdetector]

Pi machine. The schematic and Gerber files are here on the Forum.

[waltr]

Not sure if this will answer your questions:
Only beaches I've detected on have lots of black sand. The TGSL I build (plans here) beeps almost continuously so doesn't work.
The HammerHead2 with GB (see the thread "my take on the HH2") works very well but does not disc out iron so I dig lots of nails, bottle caps and other rustly things.

[yatahaze323]

Hi urge38 & waltr,

You should take a look at the Voodoo project here. Its a PI detector with true iron discrimination.

[waltr]

Hi urge38 & waltr,

You should take a look at the Voodoo project here. Its a PI detector with true iron discrimination.

Yes, I did build up the VooDoo but it is still on the bench. Maybe some day I'll finish it and test in the field or beach.

[urge38]

Is there really such a ting as a pi with true discrimination???

Fisher tried it with the AQ

It's not really discrimination though is it

[Qiaozhi]

Is there really such a ting as a pi with true discrimination???

Fisher tried it with the AQ

It's not really discrimination though is it

I believe the Fisher AQ's discrimination method is based on target conductivity, in a similar manner to the way White's TDI can eliminate small nails. It works by creating a "target hole" in the response, and any metal object with a similar value of conductivity will also fall into the hole.
Voodoo uses a completely different method, and is able to provide true non-ferrous/ferrous discrimination in the same way as a VLF.

[urge38]

Sorry to sound sceptical but
I will believe it when I see it in action

If there were such a thing as a true discrimination pi, the likes of minelab and garrett would be beaten down the door off whoever had it begging to patent it

[yatahaze323]

Well here it is in action.

[waltr]

I believe the Fisher AQ's discrimination method is based on target conductivity, in a similar manner to the way White's TDI can eliminate small nails. It works by creating a "target hole" in the response, and any metal object with a similar value of conductivity will also fall into the hole.
Voodoo uses a completely different method, and is able to provide true non-ferrous/ferrous discrimination in the same way as a VLF.

Sorry to sound sceptical but
I will believe it when I see it in action

If there were such a thing as a true discrimination pi, the likes of minelab and garrett would be beaten down the door off whoever had it begging to patent it

As I see it the VooDoo's disc is NOT a pure PI detector but uses an oscillation, more like a VLF, for the disc.
The phase a decay of the oscillation is used to disc iron verse non-iron.

I would consider the VooDoo as a hybrid instead of pure PI.

[urge38]

Anyone know of a video of it rejecting iron

[urge38]

Has anyone used one on here and wishes to verify that it rejects iron like a vlf

Or can anyone point me to a video of it in action, especially the iron rejection

[Carl-NC]

There are 2 ways to discriminate with a PI. First, sample during the TX pulse where you have access to a reactive signal. This requires the use of an IB coil and is how Minelab does iron reject on their PIs. It is more akin to VLF and not as deep as the PI side so iron ID is not available for the full PI depth.

The second way is to analyze the flyback decay. A 2-sample analysis (TDI, ImpulseAQ) is how viscous ground is rejected (a form of discrimination) and results in low/high conductivity ranges which is pseudo-discrimination. If you want better discrimination then take more samples. Most coins & rings have fairly well-behaved exponential decays while iron targets do not. It's possible with 3 or 4 samples to do a decent job of iron reject. However, later samples occur at a weaker signal level so discrimination still won't work at maximum depth.

Edit: The Voodoo is a hybrid, not strictly a PI. There are several ways to make a hybrid PI/VLF but generally the VLF side retains the depth limitations of VLF compared to the PI side. Technically, sampling during the TX pulse (above) is a hybrid approach.