How Combined Gain/Sensitivity/Discrimination settings effect depth

This is manufacturer supplied information from one of the Top 3 detector manufacturers. The detector evaluated is one of their best ever designs. It shows how the combinations of gain/sensitivity/discrimination effect the machines depth. It is air testing, not in the ground. Guessing is okay for lottery tickets, not metal detectors. As can be seen, properly applying the combinations because the ""user can knowingly"" adjust each setting, greatly increases the machines depth "potential".
In my opinion, Fisher/Teknetics users should be supplied this same level of information from First Texas Products. Especially in regards to Fisher/Teknetics disc/gain ratio information (not have to guess what the gain level is), as it is critical to proper setups and getting the maximum benefits from a machine.

Test Coin - U.S. Lincoln pre-1983 copper small cent

Detector......Disc Mode..........Sensitivity.......Disc\Inches

Spe*****... Jewelry/Beach...... 1+60............8
Spe*****... Jewelry/Beach...... 1+80............11
Spe*****... Jewelry/Beach...... 15+75..........14.2
Spe*****... Jewelry/Beach...... 15+80..........14
Spe*****... Jewelry/Beach...... 15+71..........14

Spe*****... R<70....................1+60............8
Spe*****... R<70....................1+80............11
Spe*****... R<70....................15+75..........13.5
Spe*****... R<70....................15+80..........13
Spe*****... R<70....................15+71..........12.8

Key to Interpreting Chart

Sensitivity = First # is Preamp Gain - Second # is AC Sensitivity
Preamp Gain / 1=min, 15=max
AC Sensitivity / 0=min, 80=max
Jewelry/Beach - accepting some nails through U.S. silver dollar/hotrocks
R<70 - disc rejecting up to and including a U.S. zinc Lincoln penny

note: AC Sensitivity is this mfg's term for the sensitivity specifically used only in the motion discrimination modes. Behaving just like the sensitivity adjustment on Fisher/Teknetics units when in their discrimination mode.



Edited 10 time(s). Last edit at 02/21/2011 01:15PM by TerraDigger.

Good (and interesting) post.

I noticed that last year on a beach using a ML. There was a point, which happened to be sensitivity 29, where there was no improvement in depth. I did find more sensitivity to nearby small surface targets with higher sensitivity. I agree id like to see more shared info from testing being done on detectors. It would save a lot of our time. I guess the question we would have is what if our detector didnt react the same?

Dew

TerraDigger, that's how I set up my XLT, but I have always hunted alone so I don't know if I get good depth, sometimes I dig things real deep, last year I dug a box eagle cartridge in a field in Maine, it was 18 inches deep, but it could have fallen back in, I don't think it did, it's funny, I went over it a couple of times over the years thinking it was some deep iron, but that day the signals were far and few so I dig it and was surprised, I'm digging more and more of those signals

This is surely an interesting read , but as with some companies , air tests can show a similarity to what real world depths can be , while other companies machines show no relevance to what an air test indicates at all .......This type of test would not work for all machines ...... Not only that , but once you go into other avenues of detecting such as trash in the ground , and soil conditions , and coil sizes , etc , you will soon see that it's not as simple as running air tests when coming out with any conclusions ......


What I would like to see is a shoot out at a DOCUMENTED TEST GARDEN !!...... Ground conditons would be the same , targets would be the same, depths would be the same , and let the games begin !!.....Jim

The chart was only meant to show that proper/improper adjustment of gain/sens/disc combinations significantly affects the "potential" depth capabilities of a detector. The user knowing the settings level of all 3 of these adjustments is critical to a properly setup machine. As you pointed out correctly, soil mineralization, trash, coils etc will affect real world depth.

I added "potential" to original post.....thanks for keeping me on my toes.



Edited 1 time(s). Last edit at 02/20/2011 11:22PM by TerraDigger.

Terra ,
As Tom pointed out in one of the threads here , some detectors ARE indicative of what they air test .....so it's not a bad report for that detector ....I think it was the CZ21 that he mentioned being close to what it air tests at .......My Minlelab machines are not anything like their air tests ....... and my brothers little Silver Umax is NOTHING like what it air tests at !!......There is STILL something to be said about the chart though ....It does show gains and losses with various settings ..... if these somehow equate to the ground also , it's still a valid comparison ..... I guess I'm' a little touchy on air tests , as I was in the middle of my " AT Pro falsing " escaade , and the folks from the Garrett forum were all clammering about the air tests that they were doing and it was getting to the point where these guys were thinking that they would be finding targets 18 inches under ground wtih their AT Pro !!......and they would fight you if you didn't agree with them !!...... Anytime I would speak on a subject to educate , I would get a smart a$$ remark and be told that I was a Garrett basher !!..... Thank God that's over now .......Geting ready for the NEXT madcap adventure .....LOL !!!....Jim

I don't believe Terra intended for this to have anything to do with dirt performance; rather, to sharply educate folks that 'Sens vs Disc' on some units.... will dramatically alter performance. And.......if this is what happens in an air-test........you can bet it'll respond in similar fashion in the dirt.

Agreed, and really appreciate Terra's post.

Now, if only to see such a chart on an F70/F75/T2....

Guess I'll need to do such a thing on my own...

Steve

So you're saying that if your increase your Sensitivity and your Preamp gain on these machines , and you are in highly mineralized soil that has a lot of trash that these figures will pan out ? ........ What about the " headlights in the fog " issue ? ..... Does this have no rellivance ? .... This is what I was eluding to earlier ...Jim

The post is "ONLY" meant to show the relationship of how Gain/Sensitivity/Discrimination interact with each other in affecting "ANY" detectors depth capabilities that utilizes these three features. Period!!!!!
Mineralization, trash, coils etc (valid points) are a completly different subject and not related to the intent of this post.

Oky Doky !!......Gotcha good buddy !!.....Jim

I would argue about this manufacturer being in the top 3 but that’s a whole different subject.
I put lots of hours in on this particular detector a few decades ago…..
This is like comparing apples to oranges because this unit has independent gain AND sensitivity controls and what they show here is just a small sampling of how they interact in the disc mode.
With 80 different sensitivity settings, 15 different gain settings and many different disc settings this shows a small sample of how they work together. Some are with the disc low and the other the disc is high . Most folks realize that as you turn up your disc you typically lose some depth as is shown here –this has nothing or little to do with how disc and gain interact but more with how higher disc causes a loss of depth or sensitivity. It also shows how a high gain works better with a slightly lower sensitivity….

This doesn’t show any relationship to where the discrimination setting affects gain instead it shows how the independent gain and sensitivity work together and how a higher disc affects depth.

The T2 and F75 gain can’t be adjusted so why would it matter what it is set at?

The trick is to set the unit up in a way that works for the user and that varies from location to location, hunter to hunter, type of hunting you are doing and type of target you are looking for. Run a T2 just like any other detector without a gain adjustment feature—set the disc according to what you want to discriminate out and then set the sensitivity accordingly (normally as sensitive as you can get) for maximum performance and depth. If its too noisey at a certain disc level turn down the sensitivity. If its not hot enough at a certain disc level turn up the sensitivity.

Hope this helps,

Mike

I would add:

Some detectors take a considerable amount of multi-adjusting to achieve max performance; whilst other detectors require very few adjustments....and can trump the complex detectors after all is said-and-done with their complex tuning procedures.

I'm seeing in this chart how discrimination effects depth ......Is this a byproduct of single frequency machines, or ? ........I have always been told that depth is not effected by discrimination on my E Trac , and it's even encouraged for reasons of masking ......Please explain the difference between the diffences on how discrimination effects multifrequency machines as compaired to single frequency machines , since there might be a difference .......Jim

Doesnt all detectors have coil shutdown with a disc target? Much like a sponge being squeezed as it passes over a target.... which will cause any to loose depth. That being so the more sensitivity you add the deeper the detector attempts to ID targets.... creating a larger volume of material to be processed and more shutdown.... even the Etrac.

Dew

I believe that the newest digital machines generally do not lose depth with added discrimination; this is a resultant on many early analog machines.

I've never experienced any loss on my F75 LTD. Basically, disc/notch out what you don't want to find, set the sensitivity for a silent background threshold, or a little chatter, and go hunt!

There is a degradation of audio with increased disc, especially on weak targets with delta-pitch tones, and for that reason alone I use minimal discrimination.

using a 14 month old T2 LTD 11''coil, a small c/nickle coin @55, a lead .177 airgun slug @43 in air test. Done by hand so a bit raggy.

Disc Sens .177 coin
0 60 5'' 11.5
1 '' 4 11
2 '' 3.75 10.5
3 '' 3.50 10
4 '' 3.25 9
5 '' 2 9
6 '' 1.25 8.50
7 '' 1 8.50
8 '' 1 8.25 Signals start to get louder, cut off abruptly.
9 '' 1 8.25
10 '' .75 8
15 '' 0 7
20 '' 0 6.25
20 99 3 10
20 90 1 9.25
20 80 0 8.25
30 60 0 6.25
40 '' 0 6
50 '' 0 10.50
Bp mode.
0 40 4.50 12+
1 '' 5 12
2 '' 4 11.75
3 '' 3.50 11.75
4 '' 3.25 11.50
5 '' 3.25 11.0
6 '' 3 10.75
7 '' 2.50 10.50
8 '' 2.50 10.50
9 '' 2 10.25
10 '' 2 10.0
15 '' 1 9.25
15 60 0 9.50
15 70 0 10.50
20 70 0 9.50
20 80 0 10.50
50 60 0 11
I don't understand what you mean when you say disc don't lose any depth. The figures are a bit rough but my test bed shows basically the same pattern,.... after a disc of 8 the signal tones get what appears a gain (louder) but it cuts off fast, as in,, it's there loud at full detection depth,,,, move the coil away a fraction no fade,,,, just gone.
50 disc seems to take it back to 2 disc, it chatters just the same.
Sorry about that, don't know why it's crushed all the columns up.



Edited 3 time(s). Last edit at 02/28/2011 10:28PM by Mal.

A big THANKS!!!!!!

Mal, It's a laborious process...lol...but worth it. If ya want to keep multi-column data lined up you need to use periods (.) as spacers......for example:

Disc........Sens........Depth
10..........50............9"

Mal. I took it upon myself to tidy up your results. If anything is not correct, you can copy and paste it into your post (which you should anyways) and fix it. I will remove your data from this post when you copy results back into your post.

Using a 14 month old T2 LTD, 11''coil, a small C/nickle coin @55, a lead .177 air-gun slug @43 in air test. Done by hand so a bit raggy.

IN GROUND TEST

...........................................Sens....43.............................55
Disc................................................177cal.......................Cupro/Nickle Coin.....(British 5 pence)
0 ....................................................5''.............................11.5"
1 ....................................................4...............................11
2 ....................................................3.75..........................10.5
3.....................................................3.50..........................10
4.....................................................3.25.......................... 9
5.....................................................2............................... 9
6.....................................................1.25.......................... 8.50
7.....................................................1............................... 8.50
8.....................................................1................................8.25................Signals start to get louder, cut off abruptly.
9.....................................................1................................8.25
10...................................................75..............................8.....................that's a .75 result, not 75
15...................................................0................................7
20...................................................0................................6.25
Disc....................................Sens.....................177cal..........................Cupro/Nickle Coin.....(British 5 pence)
20.......................................99........................3".................................10"
20.......................................90........................1...................................9.25
20.......................................80........................0...................................8.25
30.......................................60........................0...................................6.25
40....................................... ''.........................0...................................6
50.......................................''..........................0...................................10.50
Bp mode.
0.........................................40........................4.50"..............................12+"
1.........................................''..........................5.....................................12
2.........................................''..........................4.....................................11.75
3.........................................''..........................3.50................................11.75
4.........................................''..........................3.25................................11.50
5.........................................''..........................3.25................................11.0
6.........................................''..........................3.....................................10.75
7.........................................''..........................2.50................................10.50
8.........................................''..........................2.50................................10.50
9.........................................''..........................2.....................................10.25
10.......................................''..........................2.....................................10.0
15.......................................''..........................1......................................9.25
15......................................60.........................0......................................9.50
15......................................70.........................0......................................10.50
20......................................70.........................0......................................9.50
20......................................80.........................0......................................10.50
50......................................60.........................0......................................11
I don't understand what you mean when you say disc don't lose any depth. The figures are a bit rough but my test bed shows basically the same pattern,.... after a disc of 8 the signal tones get what appears a gain (louder) but it cuts off fast, as in,, it's there loud at full detection depth,,,, move the coil away a fraction no fade,,,, just gone.
50 disc seems to take it back to 2 disc, it chatters just the same.
Sorry about that, don't know why it's crushed all the columns up.


TerraDigger's results re-posted from "Teknetics T2 / A Gain Measurement Chart":

""Keep In Mind Indoor EMI Affects The Depth/Noise Results. Test Is Only To Show How Discrimination Adjustments on T2 Affect The Gain
(or something that acts like gain) Output""

AIR TEST

Model - Teknetics T2/Software version 6.5 (from 6.0 onwards version numbers make no difference in depth according to First Texas Products)
Coin Used - U.S. Quarter - Cupronickel
Coil - 5" DD
Sensitivity - 60
Tone Selection - 4

Discrimination Levels

0 - 9" depth reading (extremely noisy due to EMI & machines internal circuitry noise)
10 - 7" depth reading (approx 50% less noise than 0 disc setting)
21 - 6 1/2" depth reading (quiet)
30 - 6" depth reading (quiet)
40 - 6" depth reading (quiet)
49 - 5 1/2" depth reading (quiet)
50 - 9" depth reading (this is where another huge increase in Gain occurs, besides the zero setting. Same noise level as 0 disc setting)
60 - 9" depth reading (approx 50% less noise than 50 disc setting)
70 - 8 1/2" depth reading (quiet)
80 - 8" depth reading (quiet)

Observation - the Gain does not seem to follow a straight linear output as disc is increased. Notice that from 0-49 disc there is a 3 1/2" range in detection depth. From 50-80 disc there is a 1" range.

0r

If you remove the disc 0-9 results from above, there is a 1 1/2" depth range between disc 10-49 and a 1" depth range between disc 50-80.

The large gain increase at 50 and the 10-49 disc range has serious implications on how a user sets the discrimination.

Coin specifications used in both tests:

Value........5 pence British
Mass.........3.25 g
Diameter...18 mm
Thickness..1.7 mm
Comp........75%.Cu...25%.Ni

Value........5 cents U.S.
Mass.........5.0 g
Diameter...21.21 mm
Thickness..1.95 mm
Comp........75%.Cu...25%.Ni



Edited 19 time(s). Last edit at 03/02/2011 05:12AM by TerraDigger.

Thank you very much.

Also what was the Fe304 & GC reading in your coin garden soil for test, along with the Tone setting?

Thanks for the reply.



Edited 2 time(s). Last edit at 03/01/2011 09:48AM by TerraDigger.

The coin used for the test is a British 5p cupronickel 17mm x 2mm ID 55. Used as a hammered coin substitute.
The ground where I have the test bed is a particularly bad field due to mineralisation and nails, the oldest fraction of a coin from this field is part of a Tealby penny 1158/80.
The ground is .3 Fe four bars 65 GB.
What would you like to know,,,,,,,,,,, The setting with the lowest Sens and minimum Disc and deepest buried coin,,,,,,, then just turning the Disc up till it can no longer find the coin using the same settings, to ascertain the relationship between air and soil Disc effects. Or have I misunderstood.

Mal, perfect soil readings for me..............lol.............my soil here in Idaho reads .3 Fe3O4 and 48 GC. Thank you
And thanks for describing the coin used, I thought it was a canadian nickle.
I ran some air tests on my standard T2 duplicating your machine's settings/11" DD coil, and the depth results were a close duplicate of yours in standard mode. A fractional bit more depth on mine, probably due to it being air tested & the U.S. nickel having slightly more mass.



Edited 3 time(s). Last edit at 03/02/2011 05:40AM by TerraDigger.

Very good test Mal. Thx for putting forth the effort!

What I meant by my earlier comment may only be partially true; more testing is required. But I've never found a real world site that I could comfortably crank up my sensitivity above 90 so I always felt there was enough 'gain' left in the machine to reach an identical threshold (depth) given my commonly used (low) DISC settings. But I don't hunt with chatter preferring to crank up the detector volume and headphone volume.

I need to repeat some tests at DISC=20 as that seems to be the most 'desensitized' setting.

I found the 40-49 range to be the most desensitized (loss of depth) if that's what your indicating in your post. In both mine and Mal's tests using the standard non-BP mode.

I know what you mean, I can't turn the Sens up to the 90s either, there are so many variables, but as a ball park setting, if I'm using one tone and a Disc of 18/20 for the nails which is as high as I go, Sens settings of 80+ is needed to attain the same targets as say 2 tone Sens 50 and Disc 4, When a low Sens is required to combat surface small conductors.
A very unscientific post but you know what I mean,

Despite a small storm that passed through the area yesterday, we in SC have been in the midst of a drought, and that always results in a loss of depth in clean soil. So it is in my test bed...

Re: my F75 LTD:

I had difficulty IDing my 8" silver dime in CL or BP mode at my usual sensitivity levels of 10 and 50, DISC=3 and delta pitch. CL gave a good one way tone but was usually silent the opposite direction. BP gave 2-way iron grunts. Increasing sensitivities until a slight background chatter was present did not improve the tone nor the VID. Same with changing DISC; no effect, other than silencing the iron grunts.

The standard modes were silent on this 8" deep dime including when overdriven to excessive sensitivities.

My 7" deep silver dime presented another scenario and could be detected, and ID'd correctly in either mode at the low sensitivities listed above. Changing the DISC to 20, then to 50, did not appear to change the output of the machine in any discernible way. Without any masking present, the target audio and VIDs were identical to that seen using lower DISC.

I really love running the LTD with low sensitivities, high detector volumes and good headphones.

Interesting, food for thought,

Just curious.....what is the Fe304 and GC readings in your coin test garden?

Fe3O4 = 0.03
GB = 58
Best channel = 1