Ground discrimination (GB) means discriminating targets also?

[Skiron]

Hi everyone,

This is something that I strugle to understand...I will take as an example the Deus' use in saltwater beaches to make my question clear:

I often read statements like "when you GB at salt range (e.g ground phase 27), you can eliminate the salt signal, but you also eliminate any tiny gold that reads in the same salt range, like most micro jewelry"
So I understand that even if I can flip on the Salt Mode GB (0-30) on the Deus to eliminate the salt reading, I will also lose the tiny gold that reads in the same range like salt...

To also quote a very experienced member's post: "There are many items in the ground that generate a signal that is the same as the ground reading and so are missed by tuning out that ground signal"

In my inland hunting areas, my ground phase reads 75.....so I'm setting my GB manually at 75...does this means that every target that reads 75 will also be missed, or the GB scale is independent from the targets discrimination scale Even if my ground was soft with a ground phase reading let's say 88...does this means that by GB manually at 88, I will also eliminate coins that read at the same 88?

Can someone explain this to me?? GB is in fact discrimination....how this ground discrimination connects with target discrimination

Thanks

 

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[signal_line]

i see why you are confused. Ground balance and discrimination are two different things. Take the time and try it yourself. Put out a target and see what the ID number is, then set your ground balance to that number and see what happens.

But somehow i don't think you are talking about ground balance--maybe Ground Notch?

 

[Skiron]

Thanks Signal,

I'm actually talking about Ground balance, not ground Notch (but I assume the question would be the same even with the ground notch, since both have to do with ground discrimination circuit)....

The reason I'm confused is because I read the statements above from really experienced members....and I struggle to understand it:
"when you GB at salt range (e.g ground phase 27), you can eliminate the salt signal, but you also eliminate any tiny gold that reads in the same salt range, like most micro jewelry".....
"There are many items in the ground that generate a signal that is the same as the ground reading and so are missed by tuning out that ground signal"

I'll make a test for sure, but I wanted someone to clarify this for me....if I set my Deus at GB beach mode, let's say @27.....a tiny gold chain reading 27 or lower, will be detected or not

 

[Skiron]

ps. this is one of the topics that got me into thinking and started this thread:

http://www.treasurenet.com/forums/metal-detecting-gold/328494-frequency-gold.html

(Pay spacial attention on post #13 from Steve...he knows what he's talking about)

So my question remains.. ground balancing my XP in certain ground phase readings (e.g. @27 - salt range) results in missing targets with equal or less than 27 VDIs? I suppose not...but I would like to further understand the relationship between these two discrimination cisrcuits that work simultaneously.

I'll make my question more simple: let's say the ground reads 75 and we ground balance manually exactly at this number. How does the detector understands if a 75 signal is actually from the ground or from a coin in order to eliminate that signal or not?

 

[Tedyoh]

I read what he wrote and in my opinion he does not know what he is talking about....ground balance and discrimination are not the same thing nor do they do the same thing.....a ground balance number of 90 does not discriminate a non ferrous target that is 90....unless you also set your discrimination up to or at 90....forget you read what he wrote (including the part about how frequencies work) and you will be fine.

 

[vferrari]

I read what he wrote and in my opinion he does not know what he is talking about....ground balance and discrimination are not the same thing nor do they do the same thing.....a ground balance number of 90 does not discriminate a non ferrous target that is 90....unless you also set your discrimination up to or at 90....forget you read what he wrote (including the part about how frequencies work) and you will be fine.

Not sure I know who you are referring to by "he", Ted, but I personally know Steve who wrote response 13 in the thread linked by Skiron , and in my opinion he sure DOES know what he is talking about and has forgotten more about detectors and detecting than I'll ever know. That is why he runs one of the most successful, respected, and informative detecting and prospecting websites in the world.

Don't mistake misinterpretation by those reading what he is saying with a lack of knowlege on HIS part.

Without extensively elaborating or re-iterating Steve's points, let me just say this.

First of all, regarding ground balance, Steve was not saying ground balancing is the same as discrimination, he was saying that ground balance is a type of cancellation filter like discrimination. Discrimination attempts to identify ferrous (or other undesirable target ID's in the case of non-ferrous discrimination notch filter's which should not be confused with the pure audio notch that Deus uses) and filter those signals out so they are: 1) not identified to the detectorist in tone or visual ID and/or 2) prevent the iron signal from overly interfering with the ID of nearby non-ferrous targets. Deus does this VERY effectively and is the reason why Deus is killer and perhaps the best detector to use in thick iron conditions.

Similarly, a properly ground balanced machine filters out any interfering ground feedback signal that may otherwise prevent you from detecting legitimate targets.

And as with any filter, it is possible to overdo things so if you apply too much discrimination or over compensate for the ground response you will start to lose detection depth or just filter out desirable targets outright. At this point this is where the similarity between ground balance and discrimination ends. They are filtering out two different things.

Now to get to Skiron's question, the ground response for highly mineralized dirt actually falls at the BOTTOM part of the ferrous range and a salt ground response indeed hovers in the small gold range. However, the ground balance setting numbers for either dry soil or salt beach ground settings on Deus have very little correspondence to target IDs. Just as Ted said. GB 90 does not filter out targets that ring up as 90. They are just numbers that are used for reference for the purpose of enabling the user to appropriately set the ground balance against a measured ground reference reading. On Deus the salt balance numbers just happen to be lower numbers than the dry ground balance numbers but these numbers have nothing to do with target ID. XP could have just as easily set it up that the salt balance numbers were higher than the dry ground balance numbers. They don't really mean anthing other than providing a reference for the user to match readings. In fact, you can't even infer the degree of mineralization from the GB number. You need to use the separate mineralization bargraph provided on the Deus controller to ascertain that information

Regarding salt balancing - if you are properly balanced for salt, you will tend to have less sensitivity to very tiny gold, that is just the physics of induction balance metal detecting. But people are not typically prospecting for micro gold on a beach. That tradeoff is the price for obtaining vlf detector stability (i.e., reduced chattiness) on a salt sand beach (especially with a less stable, non-simultaneous multi frequency vlf detector like the Deus vs. a multi frequency vlf detector like an Equinox or Excalibur which can use the multifrequency feature to obtain a more effective salt balance, especially in variable salt concentration conditions like surf). Yes you may filter out some gold earring backs or small studs but you should still be able to hear shallower larger/more massive gold targets like rings though at limited depths in the wet salt sand which is likely not even possible if you use dry soil balancing settings.

Finally, what Steve is saying about frequency is dead on. Higher operating frequencies result in higher ground response (i.e., ground noise) especially in salt conditions. This runs counter to the fact that higher frequencies can better detect smaller targets like small jewelry. That is why if your primary target of interest is small mid-to-low conductive jewelry like gold or platinum, then using 18 khz or higher makes sense in the dry sand where there is practicalky zero ground response. However, in the wet salt sand, it is better to reduce the chattiness associated with the salt ground response. So, if you are properly salt balanced but still experiencing chattiness in wet salt sand, try lowering your Deus frequency to lower the chattiness, if necessary. Successful detecting has a lot to do with setting up your machine to best manage these tradeoffs.

As I said before, if you want to use the most capable vlf induction balance detector on a wet salt beach, multifrequency machines like Equinox are the way to go. If you want extreme depth at the beach but with little to no ferrous discrimination, get a Pulse Induction machine which detects metallic targets using a different principle than VLF induction balance machines that is not affected by the ground signal at all but gives you very little target information or ferrous discrimination other than a rough high or low conductor audio signal.

HTH.

 

[Tedyoh]

Ok so i re-read what he wrote and it's confusing / more like old technology explanation....especially the sentence "targets that read the same as the ground are also eliminated"

"It is actually simple. Ground balancing is just another discrimination circuit at work. It is also referred to as ground rejection. The detector discriminates out the ground reading. Targets that read the same as the ground are also eliminated. Targets are masked by the ground. The more ground you must discriminate out the more target masking occurs"

Bottom line....if your beach GB is 27 you will still detect a small gold ring that has a TDI of 27.....what you will not here is the salt....i guess Steve considers salt a target....

Also why does my HF coil pick up less EMI than the LF? Steve claims lower frequencies are better in high EMI areas

 

[Skiron]

Now to get to Skiron's question, the ground response for highly mineralized dirt actually falls at the BOTTOM part of the ferrous range and a salt ground response indeed hovers in the small gold range. However, the ground balance setting numbers for either dry soil or salt beach ground settings on Deus have very little correspondence to target IDs. Just as Ted said. GB 90 does not filter out targets that ring up as 90. They are just numbers that are used for reference for the purpose of enabling the user to appropriately set the ground balance against a measured ground reference reading. On Deus the salt balance numbers just happen to be lower numbers than the dry ground balance numbers but these numbers have nothing to do with target ID. XP could have just as easily set it up that the salt balance numbers were higher than the dry ground balance numbers. They don't really mean anthing other than providing a reference for the user to match readings. In fact, you can't even infer the degree of mineralization from the GB number. You need to use the separate mineralization bargraph provided on the Deus controller to ascertain that information

Regarding salt balancing - if you are properly balanced for salt, you will tend to have less sensitivity to very tiny gold, that is just the physics of induction balance metal detecting. But people are not typically prospecting for micro gold on a beach. That tradeoff is the price for obtaining vlf detector stability (i.e., reduced chattiness) on a salt sand beach (especially with a less stable, non-simultaneous multi frequency vlf detector like the Deus vs. a multi frequency vlf detector like an Equinox or Excalibur which can use the multifrequency feature to obtain a more effective salt balance, especially in variable salt concentration conditions like surf). Yes you may filter out some gold earring backs or small studs but you should still be able to hear shallower larger/more massive gold targets like rings though at limited depths in the wet salt sand which is likely not even possible if you use dry soil balancing settings.

Finally, what Steve is saying about frequency is dead on. Higher operating frequencies result in higher ground response (i.e., ground noise) especially in salt conditions. This runs counter to the fact that higher frequencies can better detect smaller targets like small jewelry. That is why if your primary target of interest is small mid-to-low conductive jewelry like gold or platinum, then using 18 khz or higher makes sense in the dry sand where there is practicalky zero ground response. However, in the wet salt sand, it is better to reduce the chattiness associated with the salt ground response. So, if you are properly salt balanced but still experiencing chattiness in wet salt sand, try lowering your Deus frequency to lower the chattiness, if necessary. Successful detecting has a lot to do with setting up your machine to best manage these tradeoffs.

HTH.

Vferarri you're the man...thanks a million, that's exactly what was confusing me between the two "discrimination" scale numbers and their relationship...It's all clear now!!!
As for the wet beach salty conditions, I have already follow your advice (from my other thread regarding eliminating seaweed chattiness) and I have lowered the frequency to eliminate the salt chattiness with great results so far...(for a VLF detector), even if I lose some little tiny gold that way.

Ted, thanks to you also....I'm glad you understood my confusion and answered to the point, thanks man


Thank you both for your responses

 

[signal_line]

Ah Gee, I was hoping i could set my ground balance to eliminate pull tabs!!!

 

[vferrari]

Ok so i re-read what he wrote and it's confusing / more like old technology explanation....especially the sentence "targets that read the same as the ground are also eliminated"

"It is actually simple. Ground balancing is just another discrimination circuit at work. It is also referred to as ground rejection. The detector discriminates out the ground reading. Targets that read the same as the ground are also eliminated. Targets are masked by the ground. The more ground you must discriminate out the more target masking occurs"

Bottom line....if your beach GB is 27 you will still detect a small gold ring that has a TDI of 27.....what you will not here is the salt....i guess Steve considers salt a target....

Also why does my HF coil pick up less EMI than the LF? Steve claims lower frequencies are better in high EMI areas

In VERY simplistic terms, VLF induction balance detectors basically sense a phase shift between the transmitted signal and the received target signal. Ground minerals even in the absence of a metallic target will result in a slight phase shift which shows up as noise. Ground balancing biases the detector to filter out or ignore this phase shift with minimal impact on the ability to detect targets from ferrous through high conductive big silver (think of clock dial or speedometer, where low conductors such as iron start at the left and the needle progressively moves through 180 degrees to the right where the high conductors are). Ground phase is at like about 0 to 10 depending on ground composition. Iron is around 10 to 90 (straight up) and low to mid conductors are around 90 to 135 and high conductors 135 to 180 roughly. Salt ground appears to a detector to fall at about 100, which is also where small gold resides. If you balance to cancel out the salt reference “slice” you will still detect ferrous below and the mid to higher conductors above, but the targets around 100 may also be cancelled out, typically small gold.

Regarding EMI and frequency, I couldn’t find where Steve said Hf was more susceptible to electromagnetic interference (EMI), he said Hf was more susceptible to picking up ground noise which is NOT what is typically considered EMI (i.e., radio frequency interference from power lines, wi fi, electric fences, transformers, cell phones, and other detectors). It is not a given in all circumstances, but I have found the HF coils, operated at the higher frequencies (i.e., at or >25 kHz) to indeed be less susceptible to EMI but more chatty in mineralized ground or on a salt beach than when operated at lower frequencies.

HTH

 

[Skiron]

Great post V....best explanation I've ever read regarding GB scale/VDI scale correlation. At least, it gave me all the answers I was seeking as a newbee.

Thank you

 

[Tedyoh]

Regarding EMI and frequency, I couldn’t find where Steve said Hf was more susceptible to electromagnetic interference (EMI), he said Hf was more susceptible to picking up ground noise which is NOT what is typically considered EMI (i.e., radio frequency interference from power lines, wi fi, electric fences, transformers, cell phones, and other detectors). It is not a given in all circumstances, but I have found the HF coils, operated at the higher frequencies (i.e., at or >25 kHz) to indeed be less susceptible to EMI but more chatty in mineralized ground or on a salt beach than when operated at lower frequencies.

HTH

Post #3 in the link the OP provided...

"There is another thing frequency does, and that is deal with electromagnetic interference (EMI). Some frequencies like the 30 and 40 kHz range get avoided due to interference issues."

 

[vferrari]

Post #3 in the link the OP provided...

"There is another thing frequency does, and that is deal with electromagnetic interference (EMI). Some frequencies like the 30 and 40 kHz range get avoided due to interference issues."

Thanks, Ted, missed that one. Yeah, my experience is just the opposite too. I think the Deus HF coils may be better shielded than the LF coils, so that helps too but even in Equinox, I find, in general, the higher single operating frequencies are more quiet to EMI though there have been some situational exceptions. It all really depends on the source of the EMI and whether the frequencies line up to be resonant with the interference.