On Ground Balance

SLGuin

US Midwest

Joined Sep 6 2020

Posted on October 10, 2020 @ 8:44 AM

As one with little technical understanding of how metal detectors work, ground balance is the least understood function and hardest to wrap the mind around. Some make reference to using ground balance beyond just a simple ground grab, but it so far has not been made explicit enough for me to understand what is being done and how it works to create a benefit. In fact I do not see what the benefit exactly is or how it works. Can any of you shed some light?

Aaron

TOP MOD
Michigan

Joined May 20 2020

Posted on October 10, 2020 @ 12:06 PM

Not claiming to be a extremely knowledgeable  on the subject either. However whenever mineralization changes, it as you probably are aware, affects depth and stability. Therefore it’s always a good idea to reground balance. If your not familiar with the area, and you think the GB may be changing a lot, try using tracking as it will constantly compensate within 50 points. Im sure Keith can provide a even more detailed explanation.

Aaron

TOP MOD
Michigan

Joined May 20 2020

Posted on October 10, 2020 @ 12:06 PM

Not claiming to be a extremely knowledgeable  on the subject either. However whenever mineralization changes, it as you probably are aware, affects depth and stability. Therefore it’s always a good idea to reground balance. If your not familiar with the area, and you think the GB may be changing a lot, try using tracking as it will constantly compensate within 50 points. Im sure Keith can provide a even more detailed explanation.

Keith Southern

MOD

Joined May 27 2020

Posted on October 10, 2020 @ 2:46 PM

Soils especially old soils that have been eroded away for eons are magnetic.Newer type soils may not be as magnetic.

A metal detector works off of a magnetic field transmission..A detector coil creates a magnetic field around the coil .

To make it simple and I'm not really a engineer type.The coils magnetic field runs on cycles.say you have a detector on 15KHZ.Or in older terms 15 Kilocycles.That's is it transmits 15,000 times a second.Thus creating a magnetic energy field.same as a radio signal broadcast.(The main difference between an audio signal and a radio signal is that an audio signal is vibrating air and a radio signal is a vibrating magnetic field)

So we are sending a magnetic field into the soil that is supposed to find metallic objects and energize these objects(creating eddy currents) and then the receive coil of the detector can pick up the energized metals(eddys) and amplify the signal once it gets back to control box and create a beep for us to hear.

Well soils that have magnetic properties can interfere with the transmission field of the coil.And can be stronger than a target burried.Say a dime at 6 inches cant be energized enough to be higher than the soil energization.Naturally occuring Iron particles in higher abundance can even stop you from hearing a 2 inch dime.

Here's where it gets tricky.Since we are using a magnetic field detector to analyze some soils that has a high magnetic field the machine is picking up the soil as a signal,Ground balance helps to tune to the soil to make the machine not report audibly the soil.A detector like you say that has ground grab is basically doing this by analyzing the soils Ferrous content and adjusting by subtracting or adding current to the circuit to make the repsonse become neutral.So now the machine can analyze a target deeper through having a new reference point to start from.Say the dime needs a thousandth of a microvolt to produce a signal at 6 inches but the soil with a factory set ground balance was telling the machine it was producing 2 thousand microvolts.well the dime would never be reported to be analyzed.The dime at 3 inches my produce 5 thousand microvolts and be heard but not at 6.the ground balance allows the machine to shift everything to extract targets eddys from the the soils background  radiation.In simplest terms think of the ground balance control either auto track or grab or manual as the ability to discriminate soil((((watch out for auto ground balance machines advertised as such,They do not auto adjust anything the shift is just set high enough to handle about 90% of a typical hunters soils.its at times set too high for soil most soil conditions)))).just like you disc foil you can disc soil.Actually discrimination was discovered by building a ground balance system by George Payne.The the problem of the foil masking is still there even though you cant hear it just like the problem of the soil is still there pulling storn signals weak.Ground balance and discrimination work off phase shift basically.

 

This one reason pulse units punch bad soil better they operate in a different way they pulse a signal into the soil with high voltages then shut off and wait and listen for anything still energized.the Soil even though mineralized will not hold a charge as long as say just a nail.so when it turns back on the soil is decayed away but a real target is still there lit up.but its not really able to discriminate.But newer designed  ones do ground balance to remove more difficult soils that hold decay .

 

The Tarsacci is sort of in the middle of this it can punch  bad soil like a pulse but discriminate like a VLF.Its sort of a hybrid unit.

 

Now I'm not a scientist or engineer etc.far from it. and some things I said was in my layman terms but was to give a picture of what happens more simplistically, the target voltage references was grabbed out of the air for more of an  illusion to give the idea .

 

 

 

 

 

 

 

 

 

SLGuin

US Midwest

Joined Sep 6 2020

Posted on October 10, 2020 @ 3:45 PM

Keith, 

Thank you for the excellent description of a complex subject.. Given this, how then does one gain benefit from raising GB above neutral and what would that benefit be? Raising it to 650 or even 800 in 550 soil is said to aid in help in target unmasking. Would that then be because it actually detunes the machine a little to poor targets thus leaving better targets which have a stronger signal to preferentially come through?

Rivers rat

UNITED KINGDOM

Joined Sep 28 2020

In reply to by SLGuin
Posted on October 10, 2020 @ 6:21 PM

Hi i will think it is the opposite if you are more sensitive to the soil you should me more sensitive to targets.Some machine when you GB tend to to GB a bit to high by lowering manually you are gaining a bit of depth but loosing on stability .Too much and it is uncomfortable ,and you won't make difference between a good and bad one.

Like having too much discrimination ,thats my 2 cents anyway .Low discri as possible i rather hear everything than have silence during my session.

 

Think as GB as a discrimination for the soil .

 

 

RR

SLGuin

US Midwest

Joined Sep 6 2020

Posted on October 10, 2020 @ 7:49 PM

The purpose of the ground balance is to null the soil signal so the detector sees anything not soil without interference from signal from the soil itself. The Tarsacci is especially good at handling bad soil and is also especially tolerant of a wide range of ground balance settings in relation to neutral.  There are some that set ground balance some distance from neutral balance for some purpose, some say to unmask and some say the salt balance works better at 650+,some say something else for some other reason. I look to make sense of this, but struggle. I would love to have a grand unified theory for everything, but life is never that simple.

I have tried GB at grab, at 650 in 550 soil, and at 800 in 550 soil. The 800 tends to be less stable and a bit chatty compared to the others, but a 550 grab and 650 sound essentially the same and no real difference in performance is apparent. It is difficult to know what is optimum for any given setting at any given site without understanding a basic rationale for choosing any given setting in the first place.

One strategy of course, is to simply try things until one arrives at the performance desired. There must be a way of deciding optimal. Or is there?

 

 

 

 

Rivers rat

UNITED KINGDOM

Joined Sep 28 2020

In reply to by SLGuin
Posted on October 11, 2020 @ 6:16 AM

My plan is in the future session will be to check those deeper sounds or whispers as i call them and play with the settings (GB,frequency,Salinity)to see if i can get a better signal.I rather run a tad hot than cold👶

 

Have a good sunday

 

 

RR

Aaron

TOP MOD
Michigan

Joined May 20 2020

Posted on October 11, 2020 @ 7:16 AM

RATT,

If your going be checking various targets w different settings first try the following...
Find the area for test and do your GB in all 4 frequencies and adjust all the various settings the way you want them. Now when you switch frequencies, the Tarsacci will remember your settings for each frequency without having to worry about reground balancing and ect. Pretty handy feature...

 

Rivers rat

UNITED KINGDOM

Joined Sep 28 2020

In reply to by Aaron
Posted on October 11, 2020 @ 8:12 AM

Thanks Aaron,it may sense now you mentioned it :) ,a useful feature for sure .But any of you guys tried the 18khz on the beach yet??????I guess it aint useful.........on Salty beaches or Salty estuary

 

RR

SLGuin

US Midwest

Joined Sep 6 2020

Posted on October 11, 2020 @ 8:39 AM

RR,

You have an excellent strategy planned. Please report what you learn, it is of great interest to all certainly.

Here, the exactly opposite is in mind. This method is going after shallow recent drops and making every effort to avoid excessive sensitivity for deep in interest of a better look at shallow targets which might have a tendency to be overly strong. The Tarsacci has surprising depth even at quite low settings however, so that is not entirely successful.

Reading up online on the use of ground balance suggests that going negative of neutral balance is known to reduce depth and sensitivity, perhaps there is an angle to try there.

S

SLGuin

US Midwest

Joined Sep 6 2020

Posted on October 11, 2020 @ 9:01 AM

Reading this thread again it seems possible some might think it is an effort to understand ground balance in general. Such is not the case. It is rather trying to understand why some set the GB positive of neutral, sometimes very far positive. To date, ground grab taken to be soil neutral has seemed best here, and grabs are taken as often as seem necessary. There seems considerable latitude in what GB settings the Tarsacci will run well at, but what is gained by going one way or another from neutral?

Intuitively it might seem that a grab with tracking might be preferred to provide optimal performance unless one wished to hold GB positive to neutral. Not using tracking here has always been preferred to avoid skewing the balance by wiggling over a target too long. Perhaps that might be unwarranted concern and be losing a benefit of available technology. Will have to try that too.

SLGuin

US Midwest

Joined Sep 6 2020

Posted on October 12, 2020 @ 6:48 AM

Not popular topics perhaps, but important to understanding. The idea in bringing these things up at all is to get enough understanding to be able to intuitively use this detector as close to optimal as might be possible to a deeply flawed human being. The only reason to do it at all is because this detector seems somehow different to VLF, without being too much like a PI either. It seems rather like the better qualities of both without so much of the downside of either. It is difficult to even know what questions to ask sometimes, but the MDT is really quite straightforward in everyday operation.

Experimenting with ground balance in our very very dry ground yesterday leaves this. Setting negative of neutral is unhelpful, and when taken very far from neutral in that direction becomes chatty in a way not useful at all rather than the chattiness of enhanced sensitivity. No benefit could be found doing that. Going positive, even to 650 in 527 soil remains quiet, but is difficult to see what if any benefit is to be had doing that in mild soil. At positive of neutral, salt balance does not seem to work any better for foil as far as can be seen working one site at a time. There could certainly be some change of some kind, but if subtle it will not be seen without some good measure of detectable metric.

The tracking function works flawlessly and is not intrusive. For most places there would be no reason to turn it off unless a positive of neutral GB was desired. Unless considerable ground change were to happen it would not be detectable by ear if tracking were disabled, as the MDT runs pretty stable anyway.

It may well be that in some sites setting above neutral can be an advantage. It works well at neutral, IDs targets well, and runs stable over a quite wide range from neutral. It does so in the most awful ground exactly as hoped and here a simple ground grab seems all it needs to do it most of the time.

For what it is worth, this is what works here.

Rivers rat

UNITED KINGDOM

Joined Sep 28 2020

In reply to by SLGuin
Posted on October 12, 2020 @ 6:59 AM

Fair enough did you find any goodies????????????👍

 

I am always careful about the tracking function on VLF has it can be too "Slow" to cope with the soil with your "fast" coil sweep.I am pretty positive the tracking which must be emitted or dealt with by a processor need to be averaging the ground condition and mineralization .I havent tried on the MDT.OR maybe there is a powerful processor i dont know.On PI if you swing to fast compare to the speed of the recalibration of the machine you will have end of sweep signals.......

I rather GB now and then than use tracking.Tracking in comfort,but we may have a price to pay, i.e Depth or Sensitivity.

The best way i will describe it is like been on Cruise control on the Mountainous  road ........i rather adjust my speed and break when needed than let the car decide👹

 

Safe drive !!!!!!or Drive fast die young looool

 

RR

SLGuin

US Midwest

Joined Sep 6 2020

Posted on October 12, 2020 @ 10:37 AM

RR,

Rather a frustrating day target wise. The super dry soil is never as good to detectors to begin with, but all the playing around with settings did not help and this was hitting new unfamiliar parks and fields. 

The benefit of strongly positive GB is still not apparent, maybe the conditions here simply do not call for it, but a little positive seems quieter with less falsing from iron. It is a little hard to tell because a little of that noise in the background is so easy to ignore and the Tarsacci is so quiet compared to previous detectors when run in disc mode. Previously it was All-Metal mode all the time, and set hot enough to have some degree of noise almost as a threshold tone added to the actual threshold tone. Curious that the silent disc mode is so preferred on this now given the exact opposite of preference then, but that was then and this is now. Also, given that this is now run in far junkier sites and still is calmer, it is easy to see why this is the new favorite detector. Is almost a meditation to run it.

The tracking seems a matter of preference not performance here. In truth, here it can be set at 650 and left there most of the time with no further ground balancing at all. No difference in performance is obvious most of the time doing that. Otherwise, when tracking is off and GB is set to neutral, the first sign of needing a rebalance is that target ID numbers start to be off a little. Easiest to see on shiny zinc pennies, probably because they are common and easy strong signals that will hit steady 14 at neutral. When they come in at 13, rebalance and they will hit 14. That only works on uncorroded zincolns. Still, tracking off is preferred like you, and some places a positive GB sounds better anyway, but it is mostly simple preference. Running tracking for a couples hours did not show much difference from being locked into a ground grab. In fact forgot about it once and set to 650 thinking to up salt balance performance and did not notice more difference than one would normally encounter simply moving to new ground.

For as near as can be told, the benefit of positive GB is mostly about how much small iron is around. GB neutral here near home is usually somewhere between 525-600. More mineralized soil might make a difference, but the more nails it has the more positive seems helpful. 

For what it is worth,

S