Vallon VMH3CS Mine Detector

[Ferric Toes]

Interesting morning out detecting!....Went early as we are heading for 37 degrees again!
Tiny staple at 6 inches....no doubt about the response from the Vallon.
Took my new 0.1g nugget with me (thanks ebay!...if you can actually call it a nugget, more like a flake!!)......on the ground can detect it with coil raised about 3 inches above it. Buried, it makes a decent signal at about 2 inches in mineralised mode.
Had the biggest loudest response from the VMH3CS that I have experienced so far!....Got quite excited....Dug down and it became louder!....at about 2.5 feet, found the side of a rusted old oil can
Depth was very very good! I can confirm that the screech the Vallon makes on lead, alloy, gold and steel all sounds a bit different...I think...

0.1gm at 3in in normal mode and 2in in mineralised mode is extremely good. We are still struggling to explain how you get that sort of sensitivity with a 2mH coil that, on a 'normal' PI, you can't sample earlier than 20uS.

Eric.

[kingswood]

0.1gm at 3in in normal mode and 2in in mineralised mode is extremely good. We are still struggling to explain how you get that sort of sensitivity with a 2mH coil that, on a 'normal' PI, you can't sample earlier than 20uS.

Eric.

I dont know either It was roughly 3 inches in mineralised mode though with the nugget sitting on the ground and the coil swinging above it (not normal mode. I have found normal mode to noisy!).

[daverave]

when i did a field test with the vallon i borrowed a selection of gold rings from a local detectorist and it was found that the vallon did well on these and even small ammo shell cases it did very well on.

[Teleno]

0.1gm at 3in in normal mode and 2in in mineralised mode is extremely good. We are still struggling to explain how you get that sort of sensitivity with a 2mH coil that, on a 'normal' PI, you can't sample earlier than 20uS.

Eric.

A normal PI discharges the coil on a resistor which causes an exponential decay. The derivative of the decay decreases with time.



Te Vallon discharges the coil on a capacitor, which causes a quarter-cosine decay. The derivative of the decay increases with time.



Targets with shorter tau respond to the derivative of the decay. Compared to a regular PI, for the same sampling delay the Vallon provides a derivative that's larger and therefore a larger signal for short tau targets.

[green]

A normal PI discharges the coil on a resistor which causes an exponential decay. The derivative of the decay decreases with time.



Te Vallon discharges the coil on a capacitor, which causes a quarter-cosine decay. The derivative of the decay increases with time.



Targets with shorter tau respond to the derivative of the decay. Compared to a regular PI, for the same sampling delay the Vallon provides a derivative that's larger and therefore a larger signal for short tau targets.

http://www.geotech1.com/forums/showt...768#post217768

Why couldn't the Vallon detect the 1x1 inch aluminum foil which would be a short tau target in the above reply?

[Teleno]

http://www.geotech1.com/forums/showt...768#post217768

Why couldn't the Vallon detect the 1x1 inch aluminum foil which would be a short tau target in the above reply?

Perhaps it has a shorter tau than the 0.1g nugget. Even if low taus are enhanced there's a minimum coil decay beyond which nothing can be detected.

[kingswood]

Righto so something was going on yesterday....I took the 0.16g gold flake out of its plastic sleeve today and sticky taped it to a piece of cardboard.. No signal whatsoever from the Vallon with the nugget on the ground. Also tried a 1inch square of aluminium cooking foil sticky taped to cardboard and no signal either!!
Can anyone explain that?? What was I picking up yesterday??!!! Even re-checked the cardboard with plastic sleeve that it came from ebay in to make sure there were no staples !!

[Chet]

Hi Kingswood
I just received a UK VMH3CS 2010 model yesterday. The smallest nugget that it will detect is a 0.3 gram at 1” with the gain at 12 in normal. Aluminum foil is too thin. Try the side of a coke can which is normally .09-.1 mm thick. I am in the process of making some more measurements. I will post them shortly.
Have a good day,
Chet

[Chet]

Hi Kingswood


The aluminum squares used below are 0.09 mm thick from the side of a coke can. Except the second 0.25” piece is from the bottom of the can and is 0.26 mm thick. Depth is in inches. The measurements are air tests inside with a high EMI environment. Sensitivity was set at 12. Detection was determined by seeing the first or second LED lite up.


Size” Depth”
0.25 Not detected
0.25 3” This one is from the bottom of the can.
0.4 1.8”
0.5 4.4”
1.0 12”
1.5 17”
1984 US Nickel 12”
2002 Australian Dime 13”


Have a good one,
Chet

[kingswood]

Hi Kingswood


The aluminum squares used below are 0.09 mm thick from the side of a coke can. Except the second 0.25” piece is from the bottom of the can and is 0.26 mm thick. Depth is in inches. The measurements are air tests inside with a high EMI environment. Sensitivity was set at 12. Detection was determined by seeing the first or second LED lite up.


Size” Depth”
0.25 Not detected
0.25 3” This one is from the bottom of the can.
0.4 1.8”
0.5 4.4”
1.0 12”
1.5 17”
1984 US Nickel 12”
2002 Australian Dime 13”


Have a good one,
Chet

Thanks for this I will cut up some Pepsi cans for next time out in the bush and see what depths I get!
The 17" on 1.5" is pretty good!
Is it true what they say that aluminium "sounds" most like gold?? (I am still quite new to detecting, especially with PI detectors!)

[6666]

Hi Chet thanks for the info, what are you calling a 2002 Australian Dime ? 5 cents

[Chet]

Hi 6666
The coin has a 10 on the backside. I do have Australian 1, 2 and 5 cent coins which I will also measure.
Chet

[Chet]

Hi Kingswood
I find that the size and shape has a lot to do with the sound. I have found some nuggets that sound like nails. Some small boot tacks that sound like sweet nuggets. So it pays to dig most everything.
Chet

[kingswood]

Hi Kingswood
I find that the size and shape has a lot to do with the sound. I have found some nuggets that sound like nails. Some small boot tacks that sound like sweet nuggets. So it pays to dig most everything.
Chet

I plan on digging everything...First rule out here apparently
Still doesnt answer why I thought I was getting a signal on the 0.16g nugget yesterday and then today nothing!..maybe I had it where something metal already was??

[Chet]

Hi Kingswood, 6666


The gold coins below are from the US mint if you want the dimensions they are on their website. Depth is in inches. The measurements are air test inside with a high EMI environment. Sensitivity was set at 12. Detection was determined by seeing the first or second LED lite up.


Size”-------------------- Depth”
0.3 gram nugget-------1.0”
0.65 gram nugget-----4.5”
0.10 oz gold coin------10.6”
0.25 oz gold coin------12”
0.50 oz gold coin------13”
1.00 oz gold coin------14”


1962 Australian 1 cent-------9.5”
1971 Australian 5 cents------10.5”
1968 Australian 2 cents------11”
1984 US Nickel-----------------12”
2002 Australian 10 cents-----13”


These are all good numbers except for the very small nuggets that it will miss.


Have a good one,
Chet