Vallon VMH3CS Mine Detector

[pustareka]

Privet Helo !

[kingswood]

Just an interesting bit of info
Went out on the weekend...spot has lots of clay that is quite salty and highly mineralised. The GPZ7000 was as noisy as anything, difficult to tame it!
I have been there previously and this time took the vallon mainly just to see if it would GB...can confirm that it was able to GB to the noisy ground very well.

[waltr]

Refer to Green's GEB thread and GB hole plots.

https://www.geotech1.com/forums/showthread.php?24120-GEB

If a Target's TC is not near the GB Hole then there should not be any deduction of the detection strength (distance).

It is only when the target TC is close to the GB Hole that the target's signal is attenuated, thus a reduction in detection distance.

[green]

My grandaughter has a small 9 carat gold ring with 4 red stones with a total weight of 1.9gm and diameter 18mm. I checked the detection range on VMH3CS with both the Normal and Mineral settings. The Mineral setting was GB'd with a lump of Australian ironstone the same as with the tests on the 1 Lev coin. The range was the same in both settings at 11" (28cm), so there was no loss with this target. The TC of the ring was measured at 5.9uS.

Eric.

[ATTACH]45726[/ATTACH]

Interesting that you don't loose any detection depth. Wouldn't expect much signal lose in mineral setting with the ring. I loose a little when not in the hole because of noise increase with GEB on. Maybe Vallon doing something different?

[Ferric Toes]

My grandaughter has a small 9 carat gold ring with 4 red stones with a total weight of 1.9gm and diameter 18mm. I checked the detection range on VMH3CS with both the Normal and Mineral settings. The Mineral setting was GB'd with a lump of Australian ironstone the same as with the tests on the 1 Lev coin. The range was the same in both settings at 11" (28cm), so there was no loss with this target. The TC of the ring was measured at 5.9uS.

Eric.

[MTammet]

I have a Excel program that simulates a PI with GEB. Charted TC vs amplitude for different TC targets. Data on left is output from simulator. Ground with a -1.07 slope was balanced by adjusting GEB sample time until integrator out with GEB on was near zero. First column is PI timing with 1000samples/second. Second column is integrator out with GEB off, third column is integrator out with GEB on(slope=-1.07). Last two columns are the target, GEB off and on. GEB off amplitude was adjusted for 1000 for each TC. GEB on is reading when GEB off is 1000. The hole is quite narrow at the bottom. Different timings and ground slope could or would effect hole shape.

I have noticed that there are several alloys which behave in similar way in mineral and normal mode. So in my opinion this GB hole in case of Vallon is quite wide. Fortunately old bronze and most hammered coins will not fall into it.

[green]

I measured the TC of the 1 Lev by the method in post 223 in the 'target response tester' thread. I get 23.2uS, which is not far removed from your 19.5uS. My measuring window was between 40 and 63uS where signal/noise ratio is still very good 3.0V and 1.1V.

[ATTACH]45655[/ATTACH]

The detection ranges I get with the VMH3CS and stock coil are 14" (35.5cm) in Normal and 7" (17.8cm) in Mineral. Mineral being balanced on Australian ironstone. My 11.5" circular coil does better at 16" (40.6cm) and 10.5" (26.7cm). All measurements are for 2 LEDs lighting consistently. I'm not sure why the 11.5" coil does better in the Mineral mode, but it definitely seems to.

With this Vallon the coin is in the hole but not at the bottom. With a TDi detector, I once filed a piece of lead so that it was not detectable in the GB setting for ironstone. However during testing it slowly started to react, which I found was due to the slight heating caused by my fingers holding it. The hole, or notch, must be quite narrow.

Eric.

I have a Excel program that simulates a PI with GEB. Charted TC vs amplitude for different TC targets. Data on left is output from simulator. Ground with a -1.07 slope was balanced by adjusting GEB sample time until integrator out with GEB on was near zero. First column is PI timing with 1000samples/second. Second column is integrator out with GEB off, third column is integrator out with GEB on(slope=-1.07). Last two columns are the target, GEB off and on. GEB off amplitude was adjusted for 1000 for each TC. GEB on is reading when GEB off is 1000. The hole is quite narrow at the bottom. Different timings and ground slope could or would effect hole shape.

[Ferric Toes]

To leave the jokes . My compliments-by raising the target temperature its conductivity decreases. This causes the decrease of the time constant of the target . And respectively to emergence from the bottom of the hole GEB .

You got it! It also happens with non-conductive ironstone resulting in noisier ground on a hot sunny day. Stones on the surface heat up while those underneath stay cool. This temperature difference give a small shift in decay rates between those in the sun and the shaded ones. Best times to search are at night or after a rainstorm when temperatures even out and ground noise is quieter.

Eric.

[Riss]

I measured the TC of the 1 Lev by the method in post 223 in the 'target response tester' thread. I get 23.2uS, which is not far removed from your 19.5uS. My measuring window was between 40 and 63uS where signal/noise ratio is still very good 3.0V and 1.1V.

[ATTACH]45655[/ATTACH]

The detection ranges I get with the VMH3CS and stock coil are 14" (35.5cm) in Normal and 7" (17.8cm) in Mineral. Mineral being balanced on Australian ironstone. My 11.5" circular coil does better at 16" (40.6cm) and 10.5" (26.7cm). All measurements are for 2 LEDs lighting consistently. I'm not sure why the 11.5" coil does better in the Mineral mode, but it definitely seems to.

With this Vallon the coin is in the hole but not at the bottom. With a TDi detector, I once filed a piece of lead so that it was not detectable in the GB setting for ironstone. However during testing it slowly started to react, which I found was due to the slight heating caused by my fingers holding it. The hole, or notch, must be quite narrow.

Eric.

To leave the jokes . My compliments-by raising the target temperature its conductivity decreases. This causes the decrease of the time constant of the target . And respectively to emergence from the bottom of the hole GEB .

[Riss]

I measured the TC of the 1 Lev by the method in post 223 in the 'target response tester' thread. I get 23.2uS, which is not far removed from your 19.5uS. My measuring window was between 40 and 63uS where signal/noise ratio is still very good 3.0V and 1.1V.

[ATTACH]45655[/ATTACH]

The detection ranges I get with the VMH3CS and stock coil are 14" (35.5cm) in Normal and 7" (17.8cm) in Mineral. Mineral being balanced on Australian ironstone. My 11.5" circular coil does better at 16" (40.6cm) and 10.5" (26.7cm). All measurements are for 2 LEDs lighting consistently. I'm not sure why the 11.5" coil does better in the Mineral mode, but it definitely seems to.

With this Vallon the coin is in the hole but not at the bottom. With a TDi detector, I once filed a piece of lead so that it was not detectable in the GB setting for ironstone. However during testing it slowly started to react, which I found was due to the slight heating caused by my fingers holding it. The hole, or notch, must be quite narrow.

Eric.

,,slight heating caused by my fingers holding it '' - well yes ! ?Piece of lead heats up because you hold it in the iron grasp ( iron hand ) of yours ,, Ferric Toes ''

[Ferric Toes]

I see the 1 lev has a TC about 19.5us. I have a 1963 20 centimes francaise with a TC about 17.5us that falls almost to the bottom of the hole with my detector with the time settings I used.

I measured the TC of the 1 Lev by the method in post 223 in the 'target response tester' thread. I get 23.2uS, which is not far removed from your 19.5uS. My measuring window was between 40 and 63uS where signal/noise ratio is still very good 3.0V and 1.1V.



The detection ranges I get with the VMH3CS and stock coil are 14" (35.5cm) in Normal and 7" (17.8cm) in Mineral. Mineral being balanced on Australian ironstone. My 11.5" circular coil does better at 16" (40.6cm) and 10.5" (26.7cm). All measurements are for 2 LEDs lighting consistently. I'm not sure why the 11.5" coil does better in the Mineral mode, but it definitely seems to.

With this Vallon the coin is in the hole but not at the bottom. With a TDi detector, I once filed a piece of lead so that it was not detectable in the GB setting for ironstone. However during testing it slowly started to react, which I found was due to the slight heating caused by my fingers holding it. The hole, or notch, must be quite narrow.

Eric.

[green]

Here is the confirmation on a log/Lin graph with the 1 Lev giving the expected exponential decay and the ironstone power law decay.

Eric.

[ATTACH]45611[/ATTACH]

I see the 1 lev has a TC about 19.5us. I have a 1963 20 centimes francaise with a TC about 17.5us that falls almost to the bottom of the hole with my detector with the time settings I used.

[Ferric Toes]

Yes, good work and I enjoy reading all posts by you guys.

The curves Eric posted are expected. The three metal target look to be Exp^(-t/Tau) whereas the Ironstone looks to be -1/t.
If plotted on a Log/Lin and log/log graph this should be obvious.

Very interesting that even this Vallon detector has a GB hole.

Here is the confirmation on a log/Lin graph with the 1 Lev giving the expected exponential decay and the ironstone power law decay.

Eric.

[MTammet]

Yes, I have had some 1st hand experience of devices used by UK Army in Afghanistan to deal with IED issues, I am not surprised that the Vallon couldn't cope with the very high RF levels!

Pete

Vallon was built to deal with printed pcb boards. Take a piece of thin copper 5mm copper tape and look at the depth in normal mode. Same with bad silver mediaeval pennies 0.19+0.22 g

mihkel

Mihkel

[Rocketdemon]

Yes, I have had some 1st hand experience of devices used by UK Army in Afghanistan to deal with IED issues, I am not surprised that the Vallon couldn't cope with the very high RF levels!

Pete