Friendly Metal Detecting Forums   Owl Engineering
List all sponsors

Go Back   Friendly Metal Detecting Forums > Detectors and Gear > All About Detectors

Reply
  
Thread Tools Display Modes
  #1  
Old 05-03-2018, 02:25 AM
ToddB64's Avatar
ToddB64 ToddB64 is offline
Elite Member
 
Join Date: Jan 2006
Location: Georgetown, Ohio, USA
Posts: 744
Default Is Sensitivity's Affect on Threshold Common ?

Greetings

In BottleCapKing's post #21 located at > Detectors and Gear > All About Detectors >Thread by Dsparil Titled:Gain , BCK says "When you increase sensitivity, you are lowering that threshold. When you decrease Sensitivity, you are raising the threshold."

The attached graphic image should help to clarify BCK's above statement.

I'm curious to know if the affect on Threshold, as described in quotes above, is common to most metal detectors that have a manual Sensitivity control.

Sans having the technical knowledge of many metal detector brands and models, I assume it might be possible to come to a fair conclusion with empirical evidence, gained from experimenting with a sample lot of different metal detectors, increasing/decreasing the Sens. and noting the affect on metal targets buried at different depths in the ground.

Hopefully there are a few knowledgeable detectorists out there who feel qualified to answer my implicit question in paragraph three.

in advance for your comments !

ToddB64
Attached Images
 

__________________
Signature:
Teknetics Gamma 6000, Tesoro Compadre, Whites Classic II, Garrett Ace250 and Pro-Pointer AT, Vibra-Probe 580, Cen-Tech Pinpointer, Lesche Digger, Tabdog Digger Replica I made, RatphonesMax Headphones, Janster Coin Probe.

Reply With Quote


  #2  
Old 05-03-2018, 03:19 AM
BlackRain's Avatar
BlackRain BlackRain is offline
Elite Member
 
Join Date: Apr 2013
Location: Fort Smith Arkansas area
Posts: 1,115
Default

One thing I like about the Nox 800 is that you can adjust the threshold level or turn it off, I turned mine off.....maybe the person you quoted isn't talking about the same threshold that I understand you to be asking about, the constant background hum.....? Maybe they are referring to the actual detection of a signal? Really dont see how the background threshold could be affected by the gain.

Sent from my SM-G950U using Tapatalk

__________________
Dig till it hurts!
Minelab Equinox 800, Xp Deus, Garrett Pro pointer

Reply With Quote


1 members found this post helpful.
  #3  
Old 05-03-2018, 04:51 AM
ghound's Avatar
ghound ghound is offline
Elite Member
 
Join Date: May 2016
Location: Northern Ireland
Posts: 1,045
Default

Raising audio gain would amplify the weaker signal to jump over the threshold, so in a kind of way it is reducing it.
Reply With Quote


  #4  
Old 05-03-2018, 06:04 AM
bibelot's Avatar
bibelot bibelot is offline
Supporter
 
Join Date: Nov 2016
Location: Avoca,NY
Posts: 1,620
Default

It'll apply to your Tesoro, should it have both threshold and sensitivity controls, the Deleon did. It is where I posted it many times in response only to fortify that you should be adjusting the threshold whenever you adjust the sensitivity levels for optimum performance. Aka machines have both but the gain is not controlled by those settings as with a Tesoro so it has a individual sensitivity, threshold and gain control, and different results from your theory.

__________________
XP Deus, Makro Racer,Makro Racer 2, Makro Multi Kruzer ,Makro multi anfibio , simplex +, orx/9" HF coil ,XP Mi-6 pointer.

Reply With Quote


  #5  
Old 05-03-2018, 06:09 AM
Rawhide's Avatar
Rawhide Rawhide is offline
Elite Member
 
Join Date: Aug 2015
Location: SouthWestern USA
Posts: 820
Default Threshold is the best thing about the F75.

Gain is gonna increase signal. But you may miss deeper targets if you run high gain and not adjust the threshold. I run threshold on the etrac and F75. The AT Pro is preset and I find 3 bars from the top does fine.

I suspect you just need a good ground balance and adjust threshold till the chatter goes away. Thats my answer and Im sticking to it.

__________________
Etrac, F75 and AT Pro. Park hunting mostly.

Reply With Quote


  #6  
Old 05-03-2018, 06:33 AM
graybeard graybeard is online now
Elite Member
 
Join Date: Feb 2013
Location: New London Ohio
Posts: 1,658
Smile

Originally Posted by Rawhide View post
Gain is gonna increase signal. But you may miss deeper targets if you run high gain and not adjust the threshold. I run threshold on the etrac and F75. The AT Pro is preset and I find 3 bars from the top does fine.

I suspect you just need a good ground balance and adjust threshold till the chatter goes away. Thats my answer and Im sticking to it.
The F75 LTD the threshold can't be heard unless it is operated in the all metal side of the detector.

The AT PRO has no threshold.
Reply With Quote


1 members found this post helpful.
  #7  
Old 05-03-2018, 07:36 PM
ToddB64's Avatar
ToddB64 ToddB64 is offline
Elite Member
 
Join Date: Jan 2006
Location: Georgetown, Ohio, USA
Posts: 744
Default Is Sensitivity's Affect on Threshold Common ?

OK, I've read and thought about all of the replies made so far and I do appreciate the responses. However, the answer to my implied question at the top of this thread seems to be getting lost in a haze of complexities involved with different metal detector brands and models. Sorry, this isn't a criticism......just a dumb way to explain my take-away at this point.

I've always thought, any brand of detector that has manual controls for Sens., Thres. and on some models Gain, that the initial detector setup, especially when you are interested in finding deeper targets, silver coins, etc., should be (a) to find a patch of "clean" ground in All Metal mode, (b) then to set the Sensitivity to Maximum, or as high as possible without intolerable EMI. The result of doing this, according to BCK's explanation (paraphrased here), is that raising Sens. lowers the Threshold bar exposing more signals from deeper targets so they can be picked up by the RX coil winding. Again, this would be a good way to setup for the deeper targets. Otherwise, if your game is cherry picking the top 5-6 inches, this might not be the setup you would choose.

I was just curious to know if BCK's explanation, along with the attached graphics image I added as a visual aid, was common to most metal detectors with manual controls for Sens., Threshold and Gain if provided.

Is it possible to give an answer that is more or less overall and inclusive for the majority of metal detector brands and models made exclusively in the USA, for example Garrett, Tesoro, White's, Fisher, Teknetics and Bounty Hunter ?

Thanks for replies to this post !

ToddB64

__________________
Signature:
Teknetics Gamma 6000, Tesoro Compadre, Whites Classic II, Garrett Ace250 and Pro-Pointer AT, Vibra-Probe 580, Cen-Tech Pinpointer, Lesche Digger, Tabdog Digger Replica I made, RatphonesMax Headphones, Janster Coin Probe.

Reply With Quote


  #8  
Old 05-03-2018, 09:08 PM
ToddB64's Avatar
ToddB64 ToddB64 is offline
Elite Member
 
Join Date: Jan 2006
Location: Georgetown, Ohio, USA
Posts: 744
Default Is Sensitivity's Affect on Threshold Common ?

Originally Posted by BlackRain View post
One thing I like about the Nox 800 is that you can adjust the threshold level or turn it off, I turned mine off.....maybe the person you quoted isn't talking about the same threshold that I understand you to be asking about, the constant background hum.....? Maybe they are referring to the actual detection of a signal? Really dont see how the background threshold could be affected by the gain.

Sent from my SM-G950U using Tapatalk
BlackRain,

Not being a graduate Engineer in electronics with emphasis on metal detector design, my current understanding is as follows: I believe the "actual detection of a signal" as you put it and the "hum" are an electronic team, i.e. as Threshold is increased, lowering the bar, this causes a concomitant increase in the hum and vice-versa. In other words, when you manually adjust the Threshold setting, there are two effects, (a) the bar depicted in the graphic image attached to post #1, is either raised or lowered, increasing or decreasing the exposure of deeper target signals to the RX coil and (b) the Threshold "Hum" is audibly greater or weaker, all depending on the Threshold setting.

As far as the background Threshold hum being affected by the Gain setting, lacking knowledge of how increasing or decreasing Gain might have an affect on anything else in the circuit, I simply can't offer an opinion on that at this time. I would have to re-read some of Monte V. Berry's tutorials, as I believe he covered how Gain works. Anyhow, I don't believe having an understanding of how adjustment of Gain might or might not affect the operation of any other circuit component's output, would be necessary to answer my subject question.

Have fun with your Nox 800 !

ToddB64

__________________
Signature:
Teknetics Gamma 6000, Tesoro Compadre, Whites Classic II, Garrett Ace250 and Pro-Pointer AT, Vibra-Probe 580, Cen-Tech Pinpointer, Lesche Digger, Tabdog Digger Replica I made, RatphonesMax Headphones, Janster Coin Probe.

Reply With Quote


  #9  
Old 05-03-2018, 11:54 PM
IDXMonster IDXMonster is offline
Elite Member
 
Join Date: Jul 2013
Location: New Glarus
Posts: 4,889
Default

The “threshold” that a person hears humming in the background, should their machine have whats called an “operating threshold”,has nothing to do with whether or not a detected target will be heard.
Whether or not a target will be detected by the machine is a function of sensitivity.
The machine has to FIRST acquire the signal that already resides within the range of the coils field. In order for a target to be detected,it has to have a return signal that is strong enough to pass over A THRESHOLD,which is akin to the amount of sensitivity being used.(See illustration)
The signal is then sent to the audio stage where the operator can use the gain to adjust the volume.
On a machine that uses an “operating threshold”, the hum of the threshold will either be silenced and replaced with an audio indication of the target, go silent as it passes over a discriminated target or keep humming. There are instances on very weak signals where even with no discrimination applied,the threshold may go silent very momentarily as the machine “sees” a target but is unable to process it correctly due to its minimal strength.
As far as I know or have ever heard of,any kind of “operating” or “monitoring” threshold whether it be in the background all of the time or used for ground balancing a silent search machine has no effect on whether or not a signal will be detected.
NOW...some machines may use “gain” as a word to describe “sensitivity”,and if this is the case then these terms and controls should really be standardized through the industry.
This is as I understand the issue at hand.
Reply With Quote


1 members found this post helpful.
  #10  
Old 05-04-2018, 06:03 PM
ToddB64's Avatar
ToddB64 ToddB64 is offline
Elite Member
 
Join Date: Jan 2006
Location: Georgetown, Ohio, USA
Posts: 744
Default Is Sensitivity's Affect on Threshold Common ?

Originally Posted by IDXMonster View post
The “threshold” that a person hears humming in the background, should their machine have whats called an “operating threshold”,has nothing to do with whether or not a detected target will be heard.
Whether or not a target will be detected by the machine is a function of sensitivity.
The machine has to FIRST acquire the signal that already resides within the range of the coils field. In order for a target to be detected,it has to have a return signal that is strong enough to pass over A THRESHOLD,which is akin to the amount of sensitivity being used.(See illustration)
The signal is then sent to the audio stage where the operator can use the gain to adjust the volume.
On a machine that uses an “operating threshold”, the hum of the threshold will either be silenced and replaced with an audio indication of the target, go silent as it passes over a discriminated target or keep humming. There are instances on very weak signals where even with no discrimination applied,the threshold may go silent very momentarily as the machine “sees” a target but is unable to process it correctly due to its minimal strength.
As far as I know or have ever heard of,any kind of “operating” or “monitoring” threshold whether it be in the background all of the time or used for ground balancing a silent search machine has no effect on whether or not a signal will be detected.
NOW...some machines may use “gain” as a word to describe “sensitivity”,and if this is the case then these terms and controls should really be standardized through the industry.
This is as I understand the issue at hand.
IDXMonster,

Really good information and helps to deepen my knowledge on Threshold operation, however, it also raises a question of "how do we determine which type of Threshold ("Operating/Monitoring" or "Sensitivity Controlled") our detectors utilize ?

If you, or another reader of this post, are unable to answer this question "off the top of the head", then I guess the options left are to (a) look for an explanation in the detector manuals, or (b) phone the detector manufacturers and ask the question.

Thanks !
Toddb64

__________________
Signature:
Teknetics Gamma 6000, Tesoro Compadre, Whites Classic II, Garrett Ace250 and Pro-Pointer AT, Vibra-Probe 580, Cen-Tech Pinpointer, Lesche Digger, Tabdog Digger Replica I made, RatphonesMax Headphones, Janster Coin Probe.


Last edited by ToddB64; 05-05-2018 at 03:34 AM. Reason: Adding more text.
Reply With Quote


  #11  
Old 05-04-2018, 08:01 PM
IDXMonster IDXMonster is offline
Elite Member
 
Join Date: Jul 2013
Location: New Glarus
Posts: 4,889
Default

Todd-an “operating threshold” is humming in the background as you’re hunting,such as on a CTX or Explorer. A Whites Classic has what I refer to as a “monitoring threshold” which is what you hear when you flip the trigger forward or pull it for momentary pinpointing. It monitors the strength of the pinpoint via modulated audio and also tells you if your ground balance is positive or negative when you “bob” the coil. With the Mr. Bill mods on the classics the threshold pot is moved to the exterior of the case so you can adjust the volume of it. But it still has no effect on target detection when the machine is in silent search mode(trigger to center).
Reply With Quote


  #12  
Old 05-05-2018, 03:19 AM
ToddB64's Avatar
ToddB64 ToddB64 is offline
Elite Member
 
Join Date: Jan 2006
Location: Georgetown, Ohio, USA
Posts: 744
Default Is Sensitivity's Affect on Threshold Common ?

Originally Posted by IDXMonster View post
Todd-an “operating threshold” is humming in the background as you’re hunting,such as on a CTX or Explorer. A Whites Classic has what I refer to as a “monitoring threshold” which is what you hear when you flip the trigger forward or pull it for momentary pinpointing. It monitors the strength of the pinpoint via modulated audio and also tells you if your ground balance is positive or negative when you “bob” the coil. With the Mr. Bill mods on the classics the threshold pot is moved to the exterior of the case so you can adjust the volume of it. But it still has no effect on target detection when the machine is in silent search mode(trigger to center).
IDXMonster,

Thanks for that! As you probably noticed from my "Signature", I have a White's Classic II detector, so your information deepens my understanding of Threshold operation on that machine.

If you don't mind, however, I would like to refer back to your previous post that seems to be differentiating two different modes of Threshold operation utilized by detector manufacturers on their various models. For example, (a) a "Monitoring" background hum that is continuous until the Transmit coil signals a target vs. (b) a Threshold that changes as Sensitivity is increased or decreased, like the imaginary bar depicted by a graphic illustration in my post #1.

With reference to my previous post copied & pasted below, please read again and try to answer the question in quotation marks in the first paragraph. I'm asking the question because, not having X-ray vision, I can't see what's happening with that Threshold bar inside the detector circuits. If I could, then it would be easy to determine whether a particular detector of mine is operating according to (b) in the above paragraph, or not. I'm relying on BCK's statements, i.e. "When you increase sensitivity, you are lowering that threshold. When you decrease Sensitivity, you are raising the threshold." to be accurate, in agreement with and that they (BCK's statements) substantiate the graphic image in post #1.

: Really good information and helps to deepen my knowledge on Threshold operation, however, it also raises a question of "how do we determine which type of Threshold ("Operating/Monitoring" or "Sensitivity Controlled") our detectors utilize ?

If you, or another reader of this post, are unable to answer this question "off the top of the head", then I guess the options left are to (a) look for an explanation in the detector manuals, or (b) phone the detector manufacturers and ask the question.
for your help!
ToddB64

__________________
Signature:
Teknetics Gamma 6000, Tesoro Compadre, Whites Classic II, Garrett Ace250 and Pro-Pointer AT, Vibra-Probe 580, Cen-Tech Pinpointer, Lesche Digger, Tabdog Digger Replica I made, RatphonesMax Headphones, Janster Coin Probe.


Last edited by ToddB64; 05-05-2018 at 04:28 AM. Reason: Adding text.
Reply With Quote


  #13  
Old 05-05-2018, 12:43 PM
adamBomb's Avatar
adamBomb adamBomb is offline
Senior Member
 
Join Date: Jul 2015
Location: Wilmington NC
Posts: 448
Default

Originally Posted by ToddB64 View post
OK, I've read and thought about all of the replies made so far and I do appreciate the responses. However, the answer to my implied question at the top of this thread seems to be getting lost in a haze of complexities involved with different metal detector brands and models. Sorry, this isn't a criticism......just a dumb way to explain my take-away at this point.

I've always thought, any brand of detector that has manual controls for Sens., Thres. and on some models Gain, that the initial detector setup, especially when you are interested in finding deeper targets, silver coins, etc., should be (a) to find a patch of "clean" ground in All Metal mode, (b) then to set the Sensitivity to Maximum, or as high as possible without intolerable EMI. The result of doing this, according to BCK's explanation (paraphrased here), is that raising Sens. lowers the Threshold bar exposing more signals from deeper targets so they can be picked up by the RX coil winding. Again, this would be a good way to setup for the deeper targets. Otherwise, if your game is cherry picking the top 5-6 inches, this might not be the setup you would choose.

I was just curious to know if BCK's explanation, along with the attached graphics image I added as a visual aid, was common to most metal detectors with manual controls for Sens., Threshold and Gain if provided.

Is it possible to give an answer that is more or less overall and inclusive for the majority of metal detector brands and models made exclusively in the USA, for example Garrett, Tesoro, White's, Fisher, Teknetics and Bounty Hunter ?

Thanks for replies to this post !

ToddB64
On the excalibur, I have found that in all metal mode, the threshold affects depth significantly no matter what the sensitivity is. As I turn threshold down, depth decreases. Now in disc mode, this isn't the case. I can actually turn sensitivity to 10 and eliminate false's by making the threshold just silent, and get more depth. Here is a video where I demonstrate this:

__________________
Nox 600, CTX, CZ21, Excalibur II, Whites DF Pi Pro, and 920i stealth scoop.

Reply With Quote


1 members found this post helpful.
  #14  
Old 05-05-2018, 01:58 PM
Rawhide's Avatar
Rawhide Rawhide is offline
Elite Member
 
Join Date: Aug 2015
Location: SouthWestern USA
Posts: 820
Default Funny thing about the F75.

Originally Posted by graybeard View post
The F75 LTD the threshold can't be heard unless it is operated in the all metal side of the detector.

The AT PRO has no threshold.
The settings on the all metal side affect the settings on discriminate side and visa versa. You should always ground balance on all metal first when setting up your F75. Threshold may not carry over directly as I have never checked, but the settings do.

Now here is a funny haha on the DST LTD2 version. You can set sens down to zero and it will still hunt. just threw that in there. Fisher set the bar high with this detector and I suspect no detector will ever come close in my opinion. There is so many features not talked about that other detectors can not do.

Now if I remember, you have a a Tesoro. From what I have seen, a lot of experienced guys keeps at least one as they really come in handy on certain hunts.

You also have to admire Garret taking all the guess work out of settings with the AT Pro. Some would complain about its build, but I live in very rough country and the AT Pro has not suffered any equipment breakage. In fact, on old trashy campsites, they continue to out hunt all other detectors no matter the cost or age. Now this is based on actual hunts in old camps, dumps, and iron and tin infested sites.

When I started out all I could afford was a economy Bounty Hunter 202, which was top dog in the 1970's. Did not take long to figure out I needed more.

With the Nox being the new kid on the block we wont hear too much about the AT Pro or F75. Etrac is still a very doable detector but depends on the ground your hunting. They all hunt, some just better than others.

__________________
Etrac, F75 and AT Pro. Park hunting mostly.

Reply With Quote


  #15  
Old 05-05-2018, 10:46 PM
ToddB64's Avatar
ToddB64 ToddB64 is offline
Elite Member
 
Join Date: Jan 2006
Location: Georgetown, Ohio, USA
Posts: 744
Default Is Sensitivity's Affect on Threshold Common ?

Originally Posted by ToddB64 View post
Greetings

In BottleCapKing's post #21 located at > Detectors and Gear > All About Detectors >Thread by Dsparil Titled:Gain , BCK says "When you increase sensitivity, you are lowering that threshold. When you decrease Sensitivity, you are raising the threshold."

The attached graphic image should help to clarify BCK's above statement.

I'm curious to know if the affect on Threshold, as described in quotes above, is common to most metal detectors that have a manual Sensitivity control.

Sans having the technical knowledge of many metal detector brands and models, I assume it might be possible to come to a fair conclusion with empirical evidence, gained from experimenting with a sample lot of different metal detectors, increasing/decreasing the Sens. and noting the affect on metal targets buried at different depths in the ground.

Hopefully there are a few knowledgeable detectorists out there who feel qualified to answer my implicit question in paragraph three.

in advance for your comments !

ToddB64
Back again

Well, after returning to Dsparil's post #1 titled Gain, reviewing that entire thread, in particular BCK's post #21 and DIGGER27's post #22 and also deciding to re-read Dave Johnson's Essay Discrimination mode "Sensitivity" and "Depth" dated April 23, 2009 at Fisher Lab and seeing that Dave's Essay was written expressly for "single frequency VLF metal detectors" I realized that my subject question was/is inappropriate and irrelevant in view of all the new metal detector circuitry designs that have hit the market over the past 9 years, moreover some of the information in the aforementioned Essay might now be passé and need updating.

Before coming to the above conclusions, I phoned Monte V. Berry, Director of AHRPS and he answered my call on his cell phone as he was driving home and if I'm remembering correctly he was returning from a group hunt at one of his favored ghost towns. Anyway, he agreed that due to all the new and numerous sophisticated designs that have come on the market over the last decade, it's almost impossible to make blanket statements about operational characteristics that would be "common" to the majority of metal detectors.

Many of the senior members here no doubt remember all the help Monte supplied, educating newbies and semi-pros alike, answering questions for years on this website. I gave him a heart-felt thanks for that. He has been a prominent figure in the metal detecting community for over 50 years and still active with a large repertoire of knowledge on the operation, design and development of metal detectors!

In conclusion, I have my answer to the subject question now; thanks to all who replied and increased my knowledge!

ToddB64

__________________
Signature:
Teknetics Gamma 6000, Tesoro Compadre, Whites Classic II, Garrett Ace250 and Pro-Pointer AT, Vibra-Probe 580, Cen-Tech Pinpointer, Lesche Digger, Tabdog Digger Replica I made, RatphonesMax Headphones, Janster Coin Probe.


Last edited by ToddB64; 05-14-2018 at 05:50 PM. Reason: Removing fisher labs URL (Not working!)
Reply With Quote


Reply


Thread Tools
Display Modes

Forum Jump


All times are GMT -4. The time now is 10:09 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2022, vBulletin Solutions, Inc.