Vallon VMH3CS Mine Detector

[stefan-s]

Yes sorry Eric,

I mean the probe.

When my vmh3cs is arrived i will make the 60cm coil to test the debt.

Stefan

Hi Stefan,
Do you mean the depth of large objects using the probe, or the depth of large objects using the standard coil?

30cm and 60cm diameter coils are available from Vallon at huge cost and for use as a UXO detector. I have made a 38cm round coil which works fine and would be great for WW2 relics. However, if it is the probe performance you want, I can do some tests.

By the way, the Vallon stick probe looks out sideways rather than downward. Maybe it is just a small rectangular coil held lengthways in a tube. My probe is a ferrite cored solenoid type coil.

Eric.

[kingswood]

30cm and 60cm diameter coils are available from Vallon at huge cost and for use as a UXO detector. I have made a 38cm round coil which works fine and would be great for WW2 relics.
Eric.

One thing in the manual that has interested me is where vallon state: "Upon switching ON the detector electronics recognizes which search head has been connected and switches over the pulse control automatically".....I dont have the expertise or the equipment to work this out, but have you tested what exactly happens to the pulses when the larger heads are connected??

[stefan-s]

Erik,


You are telling in your post #843 you are using "copper fabric tape as a shield" what is the reason tho use this?

Sorry for the many questions but i' am new to this kind of electronics.

Best regards
Stefan

[Ferric Toes]

Thanks Eric,

Nice that you are shearing all the information.

Did you tested it on large metal objects? The depth for large objects is the interesting part for ww2 guys like me.

Stefan

Hi Stefan,
Do you mean the depth of large objects using the probe, or the depth of large objects using the standard coil?

30cm and 60cm diameter coils are available from Vallon at huge cost and for use as a UXO detector. I have made a 38cm round coil which works fine and would be great for WW2 relics. However, if it is the probe performance you want, I can do some tests.

By the way, the Vallon stick probe looks out sideways rather than downward. Maybe it is just a small rectangular coil held lengthways in a tube. My probe is a ferrite cored solenoid type coil.

Eric.

[kingswood]

Basically, with standard resistive damping, the rate at which the TX current decays in the coil slows down as you approach zero current. For small objects with short eddy current decay times you need a fast switch-off, even when the current is approaching zero. The dI/dt, or rate of switch-off with time must always be faster than the time constant of the object, otherwise signal is lost. With a half cosine TX pulse cut-off shape, the rate of switch-off speeds up as the current approaches zero which gives the signal from a small target a last microsecond boost.

Eric.

Thank you

[Ferric Toes]

Righto!.....I have done much reading and I am still not sure what this actually means !!!
Can someone explain it in simple terms for the simple man ???

Basically, with standard resistive damping, the rate at which the TX current decays in the coil slows down as you approach zero current. For small objects with short eddy current decay times you need a fast switch-off, even when the current is approaching zero. The dI/dt, or rate of switch-off with time must always be faster than the time constant of the object, otherwise signal is lost. With a half cosine TX pulse cut-off shape, the rate of switch-off speeds up as the current approaches zero which gives the signal from a small target a last microsecond boost.

Eric.

[kingswood]

Thanks Eric,

Nice that you are shearing all the information.

Did you tested it on large metal objects? The depth for large objects is the interesting part for ww2 guys like me.

Stefan

I dug half a rusty tin can at 2 foot...the standard Vallon coil detected it with ease...

[stefan-s]

Thanks Eric,

Nice that you are shearing all the information.

Did you tested it on large metal objects? The depth for large objects is the interesting part for ww2 guys like me.

Stefan

[kingswood]

The late damping not only allows for early sampling, it also provides for a half-cosine I(t) at the Tx coil, which has a higher dI/dt at lower levels than the usual exponential damping. dI/dt enhances the short-time constant response.

Righto!.....I have done much reading and I am still not sure what this actually means !!!
Can someone explain it in simple terms for the simple man ???

[Ferric Toes]

I also bought a vmh3cs yesterday, hopefully it will be here next week.

Is the someone around here who have experience with the stick probe for this detector? It is made for bomb finding so maybe its very interesting for the WW2 guys (like me) here.

Or someone here does have experience tips how to make a probe buy yourself for this detector?

Hi Stefan,

Go back to post 216. Starting there, and the following posts, are to do with making a probe for the VMH3CS.

Eric.

[stefan-s]

I was wrong its not for bomb detection the vmh3cs with probe is for searching in thin woods and bushes the vxc1 is a magnetometer and yes is for bomb finding in big depth

[stefan-s]

There is also the vxc1 also with probe looks pretty much the same to me as the vmh3cs

http://www.vallon.de/products.lasso?a=uxo-detection&b=8

[stefan-s]

I also bought a vmh3cs yesterday, hopefully it will be here next week.

Is the someone around here who have experience with the stick probe for this detector? It is made for bomb finding so maybe its very interesting for the WW2 guys (like me) here.

Or someone here does have experience tips how to make a probe buy yourself for this detector?

[Carolina]

Hope we all are pleasantly surprised!!! Let us know your results please. On the beach for gold jewlery, the VALLON is a killer.
Preforms very well so far for me.

[kingswood]

Kingswood: Wish you well but not very fair for the VALLON I think. We will see though. Both coils alone weigh more than the VALLON.
3+ pounds and 4+ pounds respectively. I have swung the 14 x 13 super D and it's a beast. Good luck and fingers crossed for you.

Carolina

I am fully expecting that the 7000 is much better....Just want too see what targets I can detect and what ones I cant ...useful learning exercise!