complete project

[Davor]

Yeah, I know, and I might have something up my sleeve, but it is not nearly ripe yet, and it may end up as complete waste of time.
There is so much energy in there that goes wasted. Actually, prior to your posts I was wandering how come that no one did not notice rising current consumption and concluded that I must be reasoning wrong. Now I know better. Thanks.

[Tinkerer]

Whole point is that detection uses only a small portion of available energy, and it is not the femtoamperes that you detect, but the miliamperes that you don't. There just must be a better way of PI detection.

The TINKERERS TEM method IS a better way.

You should take a closer look at it. Probably you could also bring many further improvements to it too. I would be happy to give you all information you need to be able to come up with new and better ideas.

Opes source depends on the contributions of the beneficiaries.

Tinkerer

[Davor]

Whole point is that detection uses only a small portion of available energy, and it is not the femtoamperes that you detect, but the miliamperes that you don't. There just must be a better way of PI detection.

[Tinkerer]

So you need only a multimeter as a receiver

I guess if the multimeter was capable of measuring femto amperes, it might even work for nuggets.

I must say that I am surprised at the relative large change in power consumption. My thanks to Midas and Mechanic for bringing up the subject.

Tinkerer

[Davor]

So you need only a multimeter as a receiver

[Tinkerer]

Hi Tinkerer,

What effect does putting the coil near, say a sheet of alu foil have on efficiency?

600mA is fine for power draw, thats about what the ML's use

Cheers Mick

One square foot of 1.6mm alu plate at the center of the coil, adds about 50mA.
2 square feet of thin steel plate, 15cm above the coil, add about 100mA power consumption.

The test coil is 1m x 0.5m.

Tinkerer

[Mechanic]

Hi Tinkerer,

What effect does putting the coil near, say a sheet of alu foil have on efficiency?

600mA is fine for power draw, thats about what the ML's use

Cheers Mick

[Tinkerer]

Hi Tinkerer,

That 600ma figure you've quoted is that measured sitting on the bench or have you done some field testing? Because if its only a bench figure I don't think you can assume its going to stay constant in the real world. When you place the coil over the ground you will lose efficiency, and exactly how much needs to be determined. It could be very significant, for example lets say your 98% efficient on the bench and you drop to 90% efficiency in the field. Now you need 5 times more power to maintain the same coil current. Maybe those figures are overly pessimistic but still, I think its worth looking into.

Midas

You are right, there is a big difference between the calculated or simulated efficiency and the real power consumption with the coil sitting on a conductive reactive ground.

In this case, the simulation shows about 350mA power consumption, while, with the coil sitting 10cm above a steel mesh, the consumption is near 600mA.

I feel 600mA is an acceptable figure for a deep seeking PI, but would love to hear other opinions too.

Tinkerer

[RKC]

Hi Tinkerer,
Here are some images of the country I detect in mainly. I also like river gorges, which is similar, large obstacles, deep & shallow overburden, damp and unpredictable mountain weather etc.,

Mountain camp in auriferous country


Thick grasses, tussocks and peat mean that a deep seeking detector is required (don't look at my wife using a Gold Bug VLF, actually she did OK with it in the rocky places, nice and light for the female enthusiast)


The quarry, a quarter oz found on this particular trip.




I meant to say that peat usually means that basement will be fairly deep so a deep seeking machine is required, especially when a thick mantle of grass overlies it.

I use the slow motion filters on my Minelab at present in this area, as you do need to poke the coil in and about the grasses, it achieves much better depth this way too.

The main thoughts on miniaturization, is that fact that all the gear has to be lugged in on ones back, so the less area and weight the control box etc., consumes the more space is available for food

The rivers and lake shores would give up many troy pounds within a couple of metres of the surface, that's all that would be required. I'd even consider using a pelican case and just opening it up and making adjustments before entering the water, or wading up a gorge channel.

Presently I'm using hip mount Li-ion batteries on my Minelab, it's called a Pocket Rocket system produced by Coiltek www.docsdetecting.com/lithiumionbp.html
I can purchase extra batteries locally for about $35 US they are listed as being 6.6 AH when new and each one will run my GPX4500 for about 6 hours, 5 after a couple of years.

I recently stumbled upon Dave Emery's patented Resonance PI. I was wondering if the TEM system uses a similar approach as far as Rx is concerned? I know Dave doesn't use Caps in the TX and the TEM coil isn't in a balanced configuration, at least that's what I remember, could be wrong. here's a link to the pdf. http://www.google.com/patents/US20090045813.pdf

Sorry for the delay again, busy with quake repairs to the house, I'm situated in Christchurch New Zealand. We've had a couple of good shakes over the last couple of years.

Best regards
Kev.

G'day Kev,

Good to see you have been doing well down in Otago ... and managing to get away from the city! Enjoyed seeing the pictures of the tussock country (I think I recognise that part of the country). I can't seem to manage to get down that way these days but might make a trip next summer.

Hope your house repairs are going ahead without too many problems. With Christchurch still getting shakes it must be a nightmare trying to repair a house.

Regards,
Rob (RKC)

[Midas]

Presently I'm using hip mount Li-ion batteries on my Minelab, it's called a Pocket Rocket system produced by Coiltek www.docsdetecting.com/lithiumionbp.html
I can purchase extra batteries locally for about $35 US they are listed as being 6.6 AH when new and each one will run my GPX4500 for about 6 hours, 5 after a couple of years.


About the battery:

The TEM TX method makes very good use of the power. Therefore I like to use a high power TX at a high pulse repetition rate, like 10A peak coil current at 5000 PPS.

This consumes about 600mA out of a 12V battery.

It has the advantage of a powerful TX pulse that generates strong eddy currents in deep targets. The high repetition rate allows for integrating or stacking many samples, thus giving a good S/N.

For this, it is good to have a relatively high TX voltage, 12V is OK, more is even better. You mentioned 12V earlier, so I have started designing around this voltage, but it seems that the battery pack you mention above, is only 7.3V.

Comments?

Tinkerer

Hi Tinkerer,

That 600ma figure you've quoted is that measured sitting on the bench or have you done some field testing? Because if its only a bench figure I don't think you can assume its going to stay constant in the real world. When you place the coil over the ground you will lose efficiency, and exactly how much needs to be determined. It could be very significant, for example lets say your 98% efficient on the bench and you drop to 90% efficiency in the field. Now you need 5 times more power to maintain the same coil current. Maybe those figures are overly pessimistic but still, I think its worth looking into.

Midas

[Tinkerer]

Presently I'm using hip mount Li-ion batteries on my Minelab, it's called a Pocket Rocket system produced by Coiltek www.docsdetecting.com/lithiumionbp.html
I can purchase extra batteries locally for about $35 US they are listed as being 6.6 AH when new and each one will run my GPX4500 for about 6 hours, 5 after a couple of years.


About the battery:

The TEM TX method makes very good use of the power. Therefore I like to use a high power TX at a high pulse repetition rate, like 10A peak coil current at 5000 PPS.

This consumes about 600mA out of a 12V battery.

It has the advantage of a powerful TX pulse that generates strong eddy currents in deep targets. The high repetition rate allows for integrating or stacking many samples, thus giving a good S/N.

For this, it is good to have a relatively high TX voltage, 12V is OK, more is even better. You mentioned 12V earlier, so I have started designing around this voltage, but it seems that the battery pack you mention above, is only 7.3V.

Comments?

Tinkerer

[Tinkerer]

Yep I think you're right, and I am getting the TEM and Dave's RPI Tx all mixed up.
Burning the candle at both ends at the moment, and the cider it good this year

Cheers
Kev.

Hi Kev,

thanks for the nice pictures. I wish I could be searching for nuggets there myself. I got a better understanding of your problems now and can see the challenge to find solutions.

One more question: do you have a lot of ferrous clutter in these areas? Would good iron discrimination be a help?

It seems to me that it is a real problem to swing a large coil in this environment.
This leaves us with 2 possibilities:
Design a detector for slow swing speed, something like 0.5m/s, or
Design a non motion detector.

Tinkerer

[Tinkerer]

Hi,
I can see clearly now........
What I was trying to put before Tinkerer with this patent, but didn't elucidate sufficiently, was a combination of TEM TX with a resonant receiver as Dave has done. Something not feasible with conventional VLF due to noise issues, but perhaps achievable with RPI. The tuned Rx coil may give you your weighting factor due to the transformer function.......Just rambling on about impossibilities probably, I must build some circuits and dabble.

Cheers
Kev.

Hi everybody,

sorry I can not answer to all the posts right now, but definitely will as soon as I can find the time.
About Dave Emery's patent, I have been aware of that method quite some time before it was patented, but decided to go another way, which I believe is better.

Tinkerer

[Kev]

Hi,
I can see clearly now........
What I was trying to put before Tinkerer with this patent, but didn't elucidate sufficiently, was a combination of TEM TX with a resonant receiver as Dave has done. Something not feasible with conventional VLF due to noise issues, but perhaps achievable with RPI. The tuned Rx coil may give you your weighting factor due to the transformer function.......Just rambling on about impossibilities probably, I must build some circuits and dabble.

Cheers
Kev.

[Kev]

Unless I'm terribly wrong, this detector does not do such thing at all.

Yep I think you're right, and I am getting the TEM and Dave's RPI Tx all mixed up.
Burning the candle at both ends at the moment, and the cider it good this year

Cheers
Kev.