Vallon VMH3CS Mine Detector

[Ferric Toes]

Just a general question, the larger the mono, the less sensitive it should be to hot rocks??
I must admit I have only used the 30cm coil a few times, but dont remember digging as many rocks as I do with the std coil...
I will try the 30cm coil out there next time....
If I reduced the sensitivity, would the hot rock detection reduce also??

The 30cm coil should be better. The larger coil will average out the ground signal under the coil somewhat better. When I get time I am going to try and design an adapter for the Vallon to identify hot rocks and, hopefully, ferrous items. The crossbar in the stock coil is just right to house a horizontal ferrite rod with a winding. This configuration will form an induction balance arrangement which can be used to differentiate resistive and reactive components of the signal and hence give a measure of identification.

Eric.

[Altair]

The 30cm coil should be better. The larger coil will average out the ground signal under the coil somewhat better. When I get time I am going to try and design an adapter for the Vallon to identify hot rocks and, hopefully, ferrous items. The crossbar in the stock coil is just right to house a horizontal ferrite rod with a winding. This configuration will form an induction balance arrangement which can be used to differentiate resistive and reactive components of the signal and hence give a measure of identification.

Eric.

Wow! This would be a very interesting topic for me!

[Ferric Toes]

Wow! This would be a very interesting topic for me!

Yes, I tried it with a ferrite rod wound to give 1.5mH and positioned it in the crossbar with a scope across the coil ends; also a damping resistor is needed. By sliding the rod you can achieve a balance so that the TX waveforms disappear and you can observe differences with ferrous and non-ferrous metals. Potting the rod in the slot should be stable as the shell is very rigid. What is needed next is a preamp and sampling arrangement triggered somehow from the TX. What I visualise is a small box that clips to the shaft with some sort of visual indicator. Long way to go yet, but as you say, an interesting topic. Having sown the seed, pehaps others can try the idea as well.

Eric.

[Altair]

Yes, I tried it with a ferrite rod wound to give 1.5mH and positioned it in the crossbar with a scope across the coil ends; also a damping resistor is needed. By sliding the rod you can achieve a balance so that the TX waveforms disappear and you can observe differences with ferrous and non-ferrous metals. Potting the rod in the slot should be stable as the shell is very rigid. What is needed next is a preamp and sampling arrangement triggered somehow from the TX. What I visualise is a small box that clips to the shaft with some sort of visual indicator. Long way to go yet, but as you say, an interesting topic. Having sown the seed, pehaps others can try the idea as well.

Eric.

Eric,
thank you very much for sharing your idea!
For sure I will think about it next days; I like it!
I will try to do some measure with a scope ASAP.

[kingswood]

The 30cm coil should be better. The larger coil will average out the ground signal under the coil somewhat better. When I get time I am going to try and design an adapter for the Vallon to identify hot rocks and, hopefully, ferrous items. The crossbar in the stock coil is just right to house a horizontal ferrite rod with a winding. This configuration will form an induction balance arrangement which can be used to differentiate resistive and reactive components of the signal and hence give a measure of identification.

Eric.

Thanks Eric, I will aim to spend a bit more time with the larger coil next time then. How would dropping the sensitivity back a bit go with hot rocks??
Interesting about the rod.

[green]

Yes, I tried it with a ferrite rod wound to give 1.5mH and positioned it in the crossbar with a scope across the coil ends; also a damping resistor is needed. By sliding the rod you can achieve a balance so that the TX waveforms disappear and you can observe differences with ferrous and non-ferrous metals. Potting the rod in the slot should be stable as the shell is very rigid. What is needed next is a preamp and sampling arrangement triggered somehow from the TX. What I visualise is a small box that clips to the shaft with some sort of visual indicator. Long way to go yet, but as you say, an interesting topic. Having sown the seed, pehaps others can try the idea as well.

Eric.

I use an IB coil with my metal detector. Rx 2(8inch round coil, figure eight), Tx oval surrounding Rx. Added an extra integrator sampling during Tx. Look at output with a digital panel meter(non motion). Works good ferrous-nonferrous on the bench. When detecting the ground signal causes a problem . My son took it to try on the Lake Michigan beach(no ground signal?) but he has been busy and hasn't tried it on the beach yet. Maybe you will have better luck with your method. I still try to find a way to make it work.

[Mdtoday]

Yes, I tried it with a ferrite rod wound to give 1.5mH and positioned it in the crossbar with a scope across the coil ends; also a damping resistor is needed. By sliding the rod you can achieve a balance so that the TX waveforms disappear and you can observe differences with ferrous and non-ferrous metals. Potting the rod in the slot should be stable as the shell is very rigid. What is needed next is a preamp and sampling arrangement triggered somehow from the TX. What I visualise is a small box that clips to the shaft with some sort of visual indicator. Long way to go yet, but as you say, an interesting topic. Having sown the seed, pehaps others can try the idea as well.

Eric.

Yes, certainly a very interesting topic Eric, great idea. I might have a shot at doing this myself, thanks for sharing.

Brian

[kingswood]

Vallon: "The VMXC1 has a second mode with additional metal discrimination. The digital signal processing allows the detector to analyze the received signals and to identify the metallic nature of the object from which the signal was picked up. In this mode, the VMXC1 distinguishes between the alarms from ferrous objects or nonferrous objects"....
I shall wait until they arrive on ebay !!!

[Ferric Toes]

I use an IB coil with my metal detector. Rx 2(8inch round coil, figure eight), Tx oval surrounding Rx. Added an extra integrator sampling during Tx. Look at output with a digital panel meter(non motion). Works good ferrous-nonferrous on the bench. When detecting the ground signal causes a problem . My son took it to try on the Lake Michigan beach(no ground signal?) but he has been busy and hasn't tried it on the beach yet. Maybe you will have better luck with your method. I still try to find a way to make it work.

Hi Green,

Yes that basic method does work well on the workbench, but on mineralised ground it is no good. I never got around to trying this, but it needs to be inhibited when the detector is in GB mode. That is, until you get a signal say 3 or more LEDs lit, then the identifier circuit is enabled. It also needs to be a motion type circuit to eliminate any drift in the IB setup. Those are the basic requirements that I imagine it will need, but I expect there will be more.

Eric.

[Ferric Toes]

Vallon: "The VMXC1 has a second mode with additional metal discrimination. The digital signal processing allows the detector to analyze the received signals and to identify the metallic nature of the object from which the signal was picked up. In this mode, the VMXC1 distinguishes between the alarms from ferrous objects or nonferrous objects"....
I shall wait until they arrive on ebay !!!

I believe that the VMH3CS can be re-programmed to do this but I don't think Vallon will allow it. I doubt the VMXC1 will be on ebay any time soon.

Eric.

[Phil S]

Hi, first post I was hoping I could attach the full Vallon VMH3CS user manual - sorry if it's already been posted, I'm only on page 10 - anyway it seems / I guess I need to post more to get the attach file facility, maybe, anyway, I uploaded it (the manual) to a free file host,, I hope it's OK to post such links Take care all,, and enjoy the very useful manual

http://www.filedropper.com/gbvmh3csopermanualsoft114

I hope the link works for you,, it seems too for me

[Qiaozhi]

Hi, first post I was hoping I could attach the full Vallon VMH3CS user manual - sorry if it's already been posted, I'm only on page 10 - anyway it seems / I guess I need to post more to get the attach file facility, maybe, anyway, I uploaded it (the manual) to a free file host,, I hope it's OK to post such links Take care all,, and enjoy the very useful manual

http://www.filedropper.com/gbvmh3csopermanualsoft114

I hope the link works for you,, it seems too for me

Since you are a new member, your first post went into moderation because it had an attachment. I have now approved your post, and removed the other two duplicates.

[Phil S]

Since you are a new member, your first post went into moderation because it had an attachment. I have now approved your post, and removed the other two duplicates.

Sorry about the duplicates, my browser was playing up

[Qiaozhi]

Sorry about the duplicates, my browser was playing up

It wasn't your browser that was the problem. Your post was not visible because it was in moderation awaiting approval by Admin.

[kingswood]

A couple of hours out this morning.
First tried the Vallon with the 30cm coil. Good GB. Tried to reduce sensitivity, but was getting hot rock after hot rock
Then tried the SDC2300, easier to use but still the occasional hot rock, even with the sensitivity down.
Nasty nasty area Mix of ironstone, magnetite, shale looking stuff and quartz......Not heavily detected