Vallon VMH3CS Mine Detector

[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.

[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!).

[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]

Interesting report thanks
I've been crook for last couple of weeks so have not ventured out any.
Dont fancy that 37', we have 5 days of +30 next week
What sensitivity setting (LED) did you have the machine set to for the .1 at 2 inches ?
thats not bad.

Standard sensitivity setting...the default one that it sets to when you switch on. I think it is 12 out of 14. I did find before that when I increased the sensitivity. I got more false signals from rocks, so have kept it pretty much set to "standard". When i did try that though, I was in a really rocky area, so will try and increase it again on "better" ground.
We would love a day below 30...cant remember the last one !!

[6666]

Interesting report thanks
I've been crook for last couple of weeks so have not ventured out any.
Dont fancy that 37', we have 5 days of +30 next week
What sensitivity setting (LED) did you have the machine set to for the .1 at 2 inches ?
thats not bad.

With mine with sens LED at 12, my 1.2 gram detects at about 6 inches in air in normal mode.

[kingswood]

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...

[kingswood]

Sheepishly mentioned to the wife that I was buying a larger coil....Told her the price and she said "Oh I thought they would be more than that"...God love her
Have ordered and will be shipped soon. Cant wait to try it!!

[green]

Hi Green good chart thanks, I've been going over some of your charts recently
where do you place the target when you take a reading, is it stationary ?
Is your integrator a 1c or 2c ?
thanks

1C integrator. Stationary, most of the time over the center of the coil spaced to give a maximum signal without the over ranging the amplifier. Depending on the coil connected(1.5 to 12 inch diameter) to the bench circuit it might be positioned closer to the edge to get a good signal. Or I might change coils. The amplifier full scale is 2.5 volts. I found my scope can effect the slope if the scale is less then .5 volt/div. so I try to position the target for at least 1 volt peak change, no target to target. It's a lower cost scope but does an acceptable recording.

Just described what I do when charting decay slope out of the amplifier, no integrator. Charting amplitude vs distance. 1C integrator, target stationary located at defined position over center unless charting amplitude off center which would be defined.

[6666]

I have been using a 200mm diameter coil and wondered how much I would gain with a bigger and smaller coil. I did a test awhile back comparing a 200mm coil with 133mm and 300mm coils. Inductance and current profile the same for the three coils. Charted target distance vs integrator out. Got similar results to a chart posted in other threads. Don't know if it relates to the Vallon coils. The amplitudes crossed at (diameter A + diameter B)/4. Gain on some targets, lose on others. Still don't know what size to end up with.

Hi Green good chart thanks, I've been going over some of your charts recently
where do you place the target when you take a reading, is it stationary ?
Is your integrator a 1c or 2c ?
thanks

[green]

Another way of looking at it; you have only got to find 25gm of gold and the coil is paid for.

Eric.

Approximate. Looking at chart reply #593 the 300mm coil would be better than the 200mm coil for nuggets over 1gram, worse for nuggets less than 1gram? Something to try, find what size nugget can just be detected at(diameter A + diameter B)/4. I've found coil circumference converted to round to work for odd shaped coils.

My thoughts, appreciate being corrected if wrong.

[green]

Optimism!...I like that!!
How much deeper should I expect with the 30cm over the standard head...all things been equal??!

I have been using a 200mm diameter coil and wondered how much I would gain with a bigger and smaller coil. I did a test awhile back comparing a 200mm coil with 133mm and 300mm coils. Inductance and current profile the same for the three coils. Charted target distance vs integrator out. Got similar results to a chart posted in other threads. Don't know if it relates to the Vallon coils. The amplitudes crossed at (diameter A + diameter B)/4. Gain on some targets, lose on others. Still don't know what size to end up with.

[kingswood]

Another way of looking at it; you have only got to find 25gm of gold and the coil is paid for.

Eric.

Optimism!...I like that!!
How much deeper should I expect with the 30cm over the standard head...all things been equal??!

[Ferric Toes]

The coil will cost more than I paid for the 2 detectors !!

Another way of looking at it; you have only got to find 25gm of gold and the coil is paid for.

Eric.

[kingswood]

Think it is a reasonable good cost for a military stuff

The coil will cost more than I paid for the 2 detectors !!

[Alexismex]

Think it is a reasonable good cost for a military stuff