Vallon VMH3CS Mine Detector

[kingswood]

Kingswood:
If you have the VALLON 30cm coil, can you compare it to the stock coil to see if there is a difference in the inductance, or the resistance or the resonant frequency. Eric say he needs to stay in these same perimeters to make all his coils work. I'm curious what it is the VALLON senses as everyone else is. Auto compensation should take care of any ground effects for any of the coils I would think? I wonder just what the adjustment of the sampling window is? Also, have you been out with your friend and his Minelab?

Carolina

Hi Mate....I dont have an oscilloscope...plus I am not sure I would know how to use one if I did
I will ask around town and see if anyone knows...Failing that, I may post it to Eric for a month
Out with my friend on Wednesday coming (day off yay!!) so will report back.

[Ferric Toes]

Hi Mate....I dont have an oscilloscope...plus I am not sure I would know how to use one if I did
I will ask around town and see if anyone knows...Failing that, I may post it to Eric for a month
Out with my friend on Wednesday coming (day off yay!!) so will report back.

What I do is measure the following at the 7 pin connector on the coil shaft; centre pin live and any outer pin, ground. 1) dc resistance using a good multimeter. 2) measure the inductance with digital inductance meter. 3) measure the resonant frequency with a sine wave signal generator, oscilloscope, and inserting series resistor of, say, 47k between sig gen and coil. Scope across coil, tune sig gen from 100 - 200kHz and look for a resonant peak.

The most likely thing for the detector to sense is the resonant frequency, although I have found when making my own coils for the Vallon, than any departure from the stock coil parameters results in the detector not working, or being very noisey.

Eric.

[Carolina]

Kingswood:
Will you be taking both coils I hope. Have you done any air test on depth with the stock coil and the 30cm? I am thinking the depth should be very close the same but a few more square inch's of coverage with the 30cm? I prefer to lay my coils flat on the ground and ground balance, then swing target above the coil rather than set up horizontal on a table say. I like the ground to play a part in the test. But this is with my VLF machines. Well, that's just me. I suppose either method would give an indication of any difference.


Thanks
Carolina

[kingswood]

Kingswood:
Will you be taking both coils I hope. Have you done any air test on depth with the stock coil and the 30cm? I am thinking the depth should be very close the same but a few more square inch's of coverage with the 30cm? I prefer to lay my coils flat on the ground and ground balance, then swing target above the coil rather than set up horizontal on a table say. I like the ground to play a part in the test. But this is with my VLF machines. Well, that's just me. I suppose either method would give an indication of any difference.
Thanks
Carolina

I will be taking both coils, have them set up on separate machines I use either one depending on where I am....I have found that the larger coil is a pain to swing in some areas with lots of rocks as I keep banging into them! The elliptical is easier to use in these areas!
I havent done any accurate air tests but did post earlier that the 30cm was picking up an Aust 5c at about 18" with the coin on the ground and the Vallon swinging over it....Wasnt the most accurate test!
I was surprised by the sensitivity of the 30cm coil...Did find a metal staple at a couple of inches, which I would have expected would be to small for the bigger coil but it found it
I posted pics of some lead scrap that the 30cm found at post #1010....Again surprised me that the 30cm found these, although they were not really deep, only about 3 inches max.
So far I havent detected anything deep with the larger coil, but have dug a couple of 2 foot plus holes chasing rusty metal with the standard coil !!
I mentioned earlier that the more I use the Vallon, the more I am trusting it....When I first started it made the occasional little squeak that I put down to noise....I have now learnt to trust the machine's silent sensitivity so will essentially dig/scrape any response, not matter how small. A few times I have had just a little "squeak" that I can then replicate by swinging over it again....end up finding tiny targets like the 0.5g round lead shot.
Very good machine

[kingswood]

couple of hours out this morning...Old mined area. Lots of trash.
Detected a 0.3g steel ball bearing at about an inch.
Lots of nails, a couple of bullet leads and bits of wire.
Came back early as I keep getting an error....I will problem solve that shortly....

[kingswood]

Manual tells me its "low battery"....which is odd as the chirps when starting up sound okay.
New batteries inserted, now seems to be working okay.
Will take a spare detector on the trip on Wednesday just in case!

[Ferric Toes]

Manual tells me its "low battery"....which is odd as the chirps when starting up sound okay.
New batteries inserted, now seems to be working okay.
Will take a spare detector on the trip on Wednesday just in case!

Batteries do recover their voltage somewhat when not being used, so when you first switch on everthing seems OK. However, as the battery voltage falls the current drawn increases to maintain the same 'power'. As the voltage falls still further, up goes the current, which causes the batteries to die very quickly. This is a characteristic of the voltage converter in the Vallon so as to maintain the 10V supply to the transmitter and keep the performance constant over the full battery voltage range.

Take spare batteries on any long trip.

Eric.

[Carolina]

Kingswood:
Wondered if you have a picture with the 30cm next to the elliptical coil?

Carolina

[kingswood]

Kingswood:
Wondered if you have a picture with the 30cm next to the elliptical coil?

Carolina

No sorry...here is a pic I did post earlier of the 30cm laying on our block

[Carolina]

Thanks for the pic. Is it elliptical or round? Picture may be misleading or my old eye's.

Thanks again
Thomas

[kingswood]

Round coil
Had an interesting day out with the Vallon today and my friend with his GPZ 7000.
Vallon gold = zero.
GPZ7000 = 2 small nuggets, maybe half a gram each.
Went to 2 areas...first one laterite gravel with ironstone and quartz. Vallon was no issue here. Few hot rocks.
Second area, gave up on the Vallon and went to the 2300 as the Vallon would not GB on the magnatite. Constant signalling despite numerous efforts to GB. Was unstable and couldnt use it all
Only had one opportunity to test the Vallon and the 7000 side by side....I had an awesome signal and dug down...and down. Signal was still there !! The GPZ waved over it and nothing We put it down to ground noise.
Pics to follow

[Carolina]

Kingswood: Did you test the VALLON on the half gram "raw" gold nuggets to see the response and distance of detection? Sorry no gold for you.

Carolina

[kingswood]

Kingswood: Did you test the VALLON on the half gram "raw" gold nuggets to see the response and distance of detection? Sorry no gold for you.

Carolina

No I had already packed it up by then.
Did swing it when we first started over a couple of specimens that they had brought out...detected the larger on, wouldnt detect the smaller one. I think the larger one had abut 20 grams of gold running thru it, the smaller one much less.

[Ferric Toes]

Round coil
Had an interesting day out with the Vallon today and my friend with his GPZ 7000.
Vallon gold = zero.
GPZ7000 = 2 small nuggets, maybe half a gram each.
Went to 2 areas...first one laterite gravel with ironstone and quartz. Vallon was no issue here. Few hot rocks.
Second area, gave up on the Vallon and went to the 2300 as the Vallon would not GB on the magnatite. Constant signalling despite numerous efforts to GB. Was unstable and couldnt use it all
Only had one opportunity to test the Vallon and the 7000 side by side....I had an awesome signal and dug down...and down. Signal was still there !! The GPZ waved over it and nothing We put it down to ground noise.
Pics to follow

A few questions as I have come across these issues in the past. Was the GPZ switched off, or at least a considerable distance away to avoid any intereference? Was the Vallon only unstable when the coil was close to the ground? Did you raise the coil in the air to check stability in case electromagnetic interference was the problem?

If either of you had mobile phones, were they switched off?

Did you use both coil sizes?

I would like to know more about the 'magnetite'. Is that the general ground, or just scattered lumps on a more normal ground? Magnetite normally only has a weak effect on a PI detector, whereas maghemite is the mineral that is the cause of problem ground signals, and is unusually strong in Australia.

If you had an 'awesome signal' perhaps you should have continued digging Look forward to the pictures.

Eric.

[kingswood]

A few questions as I have come across these issues in the past. Was the GPZ switched off, or at least a considerable distance away to avoid any intereference? Was the Vallon only unstable when the coil was close to the ground? Did you raise the coil in the air to check stability in case electromagnetic interference was the problem?

If either of you had mobile phones, were they switched off?

Did you use both coil sizes?

I would like to know more about the 'magnetite'. Is that the general ground, or just scattered lumps on a more normal ground? Magnetite normally only has a weak effect on a PI detector, whereas maghemite is the mineral that is the cause of problem ground signals, and is unusually strong in Australia.

If you had an 'awesome signal' perhaps you should have continued digging Look forward to the pictures.

Eric.

Thanks Eric.
Yep the 7000 was turned off when we were close.
I didnt try the large coil in the "bad" area....Used the standard coil and and it was signalling on every swing in this area. I raised it and it actually improved a bit, but was still unstable. I was a long way from the 7000 and the other guys with a 4500 so it wasnt EMI from them. My phone was in the car too
The other guy who took us out there said it was magnetite, but it could well be maghemite. The ground was littered with it!! I have attached pics


EDIT: Looked at the geo map of the area and it does say magnetite.