Tech question for Tom or anyone...

Was just thinking... my understanding is that the "send" signal is regulated to a certain power in US and uses alot of power to increase anyway... could it be beneficial to have an aftermarket "booster" send or send/receive amplifier that you plug in between head and coil that has it's own power supply? Maybe there's something already out there like this, I don't know. Lugging a large battery is no fun, but could be placed in a spot with a cable to do a special area... My thought process is getting more depth from existing detectors.

Don't you think detector manufacturers might have thought of this many decades ago??
The answer to your question is "NO".

Further technical info can be found here:
[www.minelab.com]

Basic MD operation
Ground mineralisation,
MD basics and theory.



Edited 1 time(s). Last edit at 02/13/2015 08:25AM by Pimento.

Only on a PI detector..... transmit power has some effect on depth capabilities.

And it's my understanding that not many detectors used here in the USA are transmitting close to the regulated set power limit. If I was a betting man, I'd say some of the nautilus machines might be, others I don't know for sure.

TnSS any guess as to Why they aren't using the full amt. of power de guvmint allows?

Probably first, not necessary-no attributable performance gains, second power waster-meaning a larger power supply would be needed; hence more weight or with like power supply less run time. Would like to know where the F75LTD fits in here??? And is the boost process feature it possesses linked?????

The F75 puts something like 25 milliwatts into the coil, 90%+ of which is used making it warm (copper wire has a resistance, so if you pass a current through it, it heats up). This is constant, it doesn't change with BP boost mode etc. It will even be the same if you put a smaller/bigger coil on it.
And BP process just makes the A to D converter run as 22-bit rather than 19-bit so it can resolve signals 8 times smaller. [my understanding - I may be a bit off, you get the idea, though]



Edited 1 time(s). Last edit at 02/13/2015 09:48PM by Pimento.

Great info Pimento!

Thanks for the info all... I figured it had probably been tried long ago and surely someone here would know! Then again, something like Notka's vibrating handle... seems like someone would have thought of that years ago... thus why I spoke up rather than my usual lurking :-)

My Garrett propointer has a vibrating handle. Though it didn't have the option of turning off the beeper. It does now, of course, hehe.

Receive Sensitivity is much more important than transmit power. And 'boost process' is simply analyzing more snap-shots (timing circuitry). I believe Pimento is exacting/correct.

So, if comparing power consumption using say a F75LTD2, is overall power consumption indeed the same when using the small coil (5") vs the stock coil (7x11") ???



Edited 1 time(s). Last edit at 02/14/2015 12:37PM by tnsharpshooter.

I would say that the power consumption is not changed when different coils are used. If there is any difference, it will be trivial. The total consumption of an F75 is about 300 milliwatts, so the coil drive and it's immediately associated electronics probably only account for 50 milliwatts.
Just fer fun, I'll attempt to measure this later.

So bigger coils don't =more wire which could=more resistance/impedance which could=more current drop across said bigger coil; hence more power consumption??? And to add XP has never acknowledged lower battery run time use when using i.e. 11" coil vs say 9" coil. I believe they use the same battery (power source).



Edited 1 time(s). Last edit at 02/14/2015 01:30PM by tnsharpshooter.

And since I can't edit my above post, wouldn't a small coil yield an "effective" higher frequency compared to a larger coil while using the same single frequency detector???
One reason why small coils do better on small objects???



Edited 1 time(s). Last edit at 02/14/2015 01:52PM by tnsharpshooter.

PIMENTO: Question, since copper causes resistance/heat could the coil makers use a fiber optic cable to lessen the resistance and would this enhance power transmitted to the ground?

Hi,,,,hey I got the answers but I'm staying out of this one....Sample::::::A lot of manufactures use aluminum wire now::::Boost Process uses a different filter system to boost depth capability and to make sounds less “choppy”. Response is slightly slower, but with a slightly slower sweep target separation is still as good as the default process............I'm out of here spurt,,spurt....LoL...JJ

But JJ, isn't there a point where this becomes ineffective/impossible feat?? "Response is slightly slower, but with a slightly slower sweep target separation is still as good as the default process..".

Sigh. Will you stop sweating about the nitty gritty of how much copper wire there may or may not be etc etc. Let the designers do what they do. The F75 runs for absolutely ages on even rubbish batteries, is that not enough?
I used to race remote control electric cars, and we flattened a battery pack in 5 minutes. They were so hot afterwards, they were dropped into a bowl of cold water, and after 10 minutes, they were fast-charged in 20 minutes, with cooling fans blowing over them. Getting a bit more power or battery life etc was important. It's not important for a modern MD, surely?

No sweating here, it's currently 20 degrees. Only listed F75 as example, would expect to see same/similar outcome on most ,if not, al other detectors.



Edited 1 time(s). Last edit at 02/14/2015 02:39PM by tnsharpshooter.

tn,
Coils are made to be the same 'impedance' (AC resistance), regardless of size. (For a given detector)
So...no...the frequency should be exactly the same. Sometimes, coils aren't made properly, and the impedance will be off a little. You'll immediately notice this as a shift in TID numbers for the same item/unit.
If it's off a lot, your depth suffers.

tnsharpshooter Wrote:
-------------------------------------------------------
> And since I can't edit my above post, wouldn't a
> small coil yield an "effective" higher frequency
> compared to a larger coil while using the same
> single frequency detector???
> One reason why small coils do better on small
> objects???

So can the current direction be reversed as fast in a large coil vs small coil??

Short answer: Yes.
Electrical current travels at the speed of light.

mike


tnsharpshooter Wrote:
-------------------------------------------------------
> So can the current direction be reversed as fast
> in a large coil vs small coil??

So, say we could build a coil 4ft in diameter with the correct AC resistance, so current could still reversed in same amount of time as say a 5" diameter coil??? Is it the AC resistance that determines the time along with applied frequency???

tnsharpshooter Wrote:
-------------------------------------------------------
> So can the current direction be reversed as fast
> in a large coil vs small coil??

Long Answer - well not too long! It is impeadance not resistance we worry about. Impeadance is the combination of the resistance, capacitance, and inductance of the circut. Almost all circuits have all three but in the case of a coil the capacitance has very little impact and the circuit is primarly inductive. I learned along time ago the phrase ELI the ICE man (Voltage E leads Current I in an inductive curcit L - and Current I leads Voltage E in a Capacitive circuit C. In a Inductive circut (like a coil the Voltage changes leads the current change - so in a coil when the current changes direction the inductor's (coil) resits the change in current. So the current changes later then the voltage changes. In a capacitive ciurcuit the reverse is true current changes and voltage change lags. The resistance of a coil to the change in current is called inductive reactance. XL

So to answer your question - the impeadance of the inductive circuit( the combination of resistance and inductive reactance in coils made for a certain metal detector) should be the same since the input circuit on the reciver end is tuned to a particular impeadance. So it does not matter if the resistance is different between the coils of different sizes - the resulting impeadance will be the same be cause the coil designers makes sure they have the same impeadance.

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

So was that a yes or no??? So the time it takes to reverse the current is the same?? Big coil vs small.

In your example, basically...Yes.

If the inductance and capacitive reactance is the same...which it should be...physical size doesn't matter.
The coil is designed to have an optimal 'Q' at a specific frequency. Electron flow, per se, has no inertia.

mike

tnsharpshooter Wrote:
-------------------------------------------------------
> So was that a yes or no??? So the time it takes
> to reverse the current is the same?? Big coil vs
> small.



Edited 1 time(s). Last edit at 02/15/2015 06:59AM by Mike in CO.

tn,
Darn. Got caught in the "only one edit" limit.

Meant to add after the 'no inertia' line the phrase..." other than that imposed by the impedance effect."
In other words...the speed or frequency that a coil operates at (or 'switches-current-back-and-forth', as you say) is precisely calculated as an electrical property.
It's not slower or faster based on physical size. It's slower or faster based on it's designed and constructed operating frequency, and if the impedance doesn't match, it's non-optimal.

In audio circuits, it's called 'impedance matching' to make sure the power transfer is as good/effecient as possible. In power distribution systems, it's called 'transmission line analysis and zero-loss impedance balancing' to prevent costly power loss.

I had a professor (that worked for NASA during the Mercury, Gemini, and Apollo programs) who would always smile and say, "It all works with FM anyway...you know...magic."

mike



Edited 1 time(s). Last edit at 02/15/2015 07:40AM by Mike in CO.

Thanks Mike and Bryanna Girl. Reading both of your responses, I now understand.