Ground balance?

[Scottowl]

I was just wondering if someone could define ground balance for me?
I do understand some soil has more minerals than others, and things do not necesarilly have to be metallic to conduct electricity.
Ground balancing discriminates out the signals given off by the soil. Is that even close to true?
Also, what are the terms positive ground balance and negative ground balance? What conditions call for one or the other?
Some machines are capable of manual ground balance. How is that accomplished?
There's more to this detecting stuff than just BEEP...DIG!
I would just like a little more info than I now have to help me understand how different machines work.

 

[Tom Slick]

There are others out there much more articulate than me and I'm sure they will chime in but here it goes. Ground balancing is setting the detector to ignore the ground mineralization. If the detector is ignoring the minerals than it is easier for it to pick up a metal target. Some detectors have a factory preset ground balance setting that allows it to work in the majority of sites. Next there is Automatic and Manual ground balancing. These allow a detector operator to adjust the ground balance so this makes a detector perform better and achieve maximum depth in more areas or sites than a preset GB detector, and also allows the detector to perform at its peak when switching from one coil to another. The difference between the auto and the manual GB is that the manual GB requires the operator to turn a knob and the auto only takes the push of a button, both while bobbing the coil up and down towards the ground. Next we have detectors with ground tracking and these enable the detector to actually adjust the GB itself to changing ground mineralization. This ground tracking keeps the detector ground balanced while the operator is swinging along. Positive ground balance is when the detector responds positive (Threshold gets louder) as the coil goes down towards the ground. Negative GB is when the threshold sound gets quieter as the coil approaches the ground or louder as the coil goes up away from the ground. The benefit of a positive GB is that the detector usually responds to smaller targets or lower conductive targets better. A negative GB can Help reduce false signals from hot rocks or some highly mineralized soil.

 

[vlad]

http://jb-ms.com/Baron/
Also Successful Coin Hunting, or a number of other books Charles Garrett wrote-other people published with him too.

 

[airscapes]

Yes, it is an internal circuit completely separate from your user controlled discrimination circuit. It's full name, at least what Whites calls it, is Ground Elimination Balance. It is the process that determines the VDI of the minerals in the ground and then eliminates them as being read as an actual Target.
Ground Tracking or Auto Track is the ability of the machine to monitor the non target ground VDI and adjust as it changes. The way the machine can tell a real target from the ground is that the ground signal changes very slowly it is not a here and then gone signal like when you pass over a good target.
This is why folks sometimes turn off autotrack when in a nail infested site. There is no slow changing ground signal with so many nails or iron that the machine balance to the nails rather than the ground...
Hope that helps

 

[MI-AuAg]

Well said Tom!

 

[WV62]

So are we talking hunting in disc or AM?

I have a machine that has auto ground tracking, but only tracks the ground in AM, when I go to disc it is running in a factory pre-set GB.

I have another machine that has what they call ground grab for most ground balancing and it also has a manual GB for those hard to balance areas. The manual doesn't say and I have no idea if the GB carries over to disc or is just for AM.

Ron in WV

 

[MI-AuAg]

So are we talking hunting in disc or AM?

I have a machine that has auto ground tracking, but only tracks the ground in AM, when I go to disc it is running in a factory pre-set GB.

I have another machine that has what they call ground grab for most ground balancing and it also has a manual GB for those hard to balance areas. The manual doesn't say and I have no idea if the GB carries over to disc or is just for AM.

Ron in WV

Hi Ron,

I'm guessing the first machine mentioned, is a Tesoro Lobo ST? One way to find out what mode your GB will work in, is to find some known difficult ground with some black sand (magnetite) or something similar. Try it in both modes. If it stays balanced in both modes in difficult ground it probably carries over. If it goes squirrely, and won't smooth out when you hit the grab button in one mode or the other, it MAY not.

 

[WV62]

Hello Ml-AuAg,

Thanks for the answer, now if I could find such a place and test my other detector.

Had a hard time getting the smile off my face when you named my detector, you are right Tesoro Lobo St. The other is a Fisher F75Ltd.

Now that the secret is out maybe somebody can just tell me if GB carries over to Disc on the F75.

Ron in WV

So are we talking hunting in disc or AM?

I have a machine that has auto ground tracking, but only tracks the ground in AM, when I go to disc it is running in a factory pre-set GB.

I have another machine that has what they call ground grab for most ground balancing and it also has a manual GB for those hard to balance areas. The manual doesn't say and I have no idea if the GB carries over to disc or is just for AM.

Ron in WV

Hi Ron,

I'm guessing the first machine mentioned, is a Tesoro Lobo ST? One way to find out what mode your GB will work in, is to find some known difficult ground with some black sand (magnetite) or something similar. Try it in both modes. If it stays balanced in both modes in difficult ground it probably carries over. If it goes squirrely, and won't smooth out when you hit the grab button in one mode or the other, it MAY not.

 

[ironsight]

One other thing to keep in mind regarding manual ground balancing is to perform it in an area void of real targets in the ground especially in an area with dense junk in it.
Otherwise, the ground balance algorithm will factor in the soil along with any junk or targets under the coil resulting in poor sensitivity for real targets.

 

[sprchng]

GB does carry over on the F75se from AM to disc but I think you have to go into AM in order to manually GB or do an offset and then go back to disc to use that setting. The fast grab is very accurate and I use it frequently in disc since the detector does not have GB tracking which would be nice. Perhaps they will update to that with F75se3 model

 

[MI-AuAg]

GB does carry over on the F75se from AM to disc but I think you have to go into AM in order to manually GB or do an offset and then go back to disc to use that setting. The fast grab is very accurate and I use it frequently in disc since the detector does not have GB tracking which would be nice. Perhaps they will update to that with F75se3 model

Hey sprchng,

I believe I was reading some material by Dave Johnson, chief design engineer with Fisher, First Texas. I think, the current preferred ground balance system there, is the manual balance with ground grab. No auto tracking. (for now anyway)

One of my detectors is a Whites GMT, a dedicated gold nugget machine, also a Dave Johnson design. It has the choice of auto tracking, manual balancing, with the grab feature that can be utilized in either mode. It is really nice to have the choice of tracking, or manual. I agree, the grab feature is very nice!

Perhaps DJ will chime in, as I know he posts from time to time.

 

[5900_XL-1]

This GB aspect has always bothered my scientific mind. There's been many machines built with a fixed GB and these machines, in competent hands compete dmned well in organized hunts where higher end detectors are being used. In fact, it's my observation that for the bulk of treasures found per-minute...the fixed GB units gather in more targets that those units with the auto and manual GB.

Folks might just be making too much out of ground balancing. Think about it. When a semi novice, running a machine with fixed GB actually leads or comes close to the same clad and treasure count as all the $1000 detector models using AT and manual GB...where's the real advantage, EXCEPT someone possibly finding a treasure a couple inches deeper.

I just wonder if GB is to a degree, hype. To add to this, I've balanced right over good targets and gotten no outstanding differences. The good target was still as detectable as with a GB to the side in clean ground. I woulda thought the good target would be eliminated.

 

[Dave J.]

Searching in All Metals, ground balance is a necessity to get decent depth in most soils. The only machine we manufacture with an "autotune" (first derivative response) all metals mode that doesn't have an explicit means of ground balancing, is the Teknetics Delta-- which also has a fixed-phase all metals mode based on motion discrimination for knocking out the ground signal in places where the first derivative all metals system is too noisy on the ground.

I mostly agree with 5900, searching in disc mode for shallow and medium depth targets, in most ground, there's very little difference in performance between fixed-phase ground balance and variable ground balance circuits/algorithms. In public parks and tot-lotting you darn well better not be digging targets 10 inches (25 cm) deep even if the machine can find targets that deep. I've known people swinging the lowly BH Tracker 4 (air test about 6 inches) who could clean up in parks and schoolyards better than most people swinging $1,000 machines because the people with the fancy machines were trying to run at high sensitivity and fighting electrical interference and iron masking.

Regarding the issue of "carrying ground balance over to disc mode from all metals", a general rule of thumb is this:

1. The older machines that were mostly analog circuits without very much if anything being done in a microcomputer, ground balance doesn't carry over to disc. This is because to do it right requires additional circuitry and in most cases the engineer figured the extra cost didn't buy enough extra performance to make it worth the trouble.

2. Most of the newer designs do most of the signal processing in a microcomputer, and carrying ground balance over from all metals to disc mode adds little or no manufacturing cost and not much additional software engineering work. So on machines that have some form of variable ground balancing, it usually carries over to disc mode.

There are a few exceptions to the above rules of thumb, but in general they hold true.

 

[MI-AuAg]

Thanks for the input DJ. It's always nice to get feedback from the perspective of a design engineer!

 

[Scottowl]

Wow! I'm in overload mode right noe!
This is a ton of great info all thru this thread.
Thanks, everyone!!