To discriminate or not

[Willee - Texas]

Will using discrimination decrease the sensitivity or depth like on some other detectors?

 

[Larry (IL)]

Will using discrimination decrease the sensitivity or depth like on some other detectors?

I don't think it does Willee, at least it shouldn't. Since the CTX does not have an all metal search mode, I think you are hunting in Discrimination mode full time whether you have an open screen or not. When using discrimination, you are rejecting the audio response of a target, not the target itself, so in other words, you have 1500 notch audio filters.

The rejected audio pixels may affect the audio response of the accepted targets though and if you do use discrimination, don't cut yourself too thin on the accepted target range. An open screen will give you the best audio response on all targets and lets you make a better decision whether to dig or not. That is where dual screens comes in handy, one discrimination pattern and an open screen with the push of a button.

I hunt with a lot of discrimination to give my mind a break and check suspect targets with the open screen pattern and a side step 180 degrees.

 

[amberjack]

I been using combined mode for 4 years and so I been hunting with 5 tones and a open screen and dirt hunting is zinc and up, beach everything.

I use an open screen 99% of the time I set the Hz of the tones 4 years ago and haven't changed them.

point is after time really don't even have think the tones pull me up.

its not perfect but it works pretty good.

I think like Larry said you notch stuff out you will miss stuff.

but its kool I don't mind hunting behind notchers

AJ

 

[GKMan]

Sorry a little late to this thread. There was a lot of good responses and perspectives.

Since the CTX first came out and before it with my Etrac, Explorer and then way back in my Sovereign days I ran as little discrimination/notching as possible. I was taught early on from undoubtedly the most successful detectorist I know that you shouldn't discriminate since you may simply be missing something. Of course technology has changed and hopefully improved over the years but still I can't imaging detecting using a discrimination pattern. My feelings are based on what I have used so long rather than saying it really is better to run open than not. I think I would feel pretty darn lonely out there not hearing practically everything the detector was trying to tell me unfiltered by discrimination.

Honestly, the thread has made me want to load up a couple of the patterns and just revisit discrimination after so many years.

 

[amberjack]

my old friend disc

he is ok but only in small doses !

AJ

 

[spede777]

yes

 

[Johnnyanglo]

I've done a similar horizontal test with iron nail perpendicular to the swing axis and separated at various distance from a penny, using the E-Trac and CTX.

What I found for the CTX is that at a horizontal separation of closer than 1" the TID falls into the DISC'd area (you get the red cursor. In other words, when the penny/nail are 3" apart the TID reads 15-39 (Fe-Co), only a bit negatively pulled into iron (penny air tests at 12Fe). But as the nail gets closer than 1" apart the nail drives down the TID into the iron at ~28Fe.

Comparing the results above with an Open Pattern (no DISC) with the CTX the TID result is very similar as the DISC'd pattern. The cursor bobbles around 28Fe to 30Fe closer than 1" apart. If the sweep height is anything above a scrub (<1/4") over the coin/nail when within 1" of each other the audio will always be either nothing (due to the DISC'd area) or a Low Iron tone (in Open Screen). In either case you wouldn't dig the coin as it looks like IRON (and sounds like iron).

What does that mean? It means if you are using a Ferrous tonal pattern in fields of iron, like TTF/4TF (18Fe-35Fe is low tone in TTF and 31Fe-35Fe is low tone in 4TF), the coin in iron will have a TID that says "don't dig me" and an audio that is silent (falls into the DISC'd zone) or in Open Screen a low iron tone with the CTX.

Is that a good idea? Not really. The CTX audio is telling you nothing but iron is there (or remains silent as the DISC eliminates the audio). You have no chance of getting the non-ferrous coin deeper than 1/2" in fields of close iron. Even when an iron nail is 3" away horizontally from the coin - and the coin is more than 3" from the coil, the TID cursor will still record ~29Fe (iron). Understand that in a field of iron it is likely that some elongated iron pieces are closer than 3" apart from your target coin, and the coin is likely to be deeper than 3" down.

Now, if you switch from ferrous (TTF/4TF) to conductive, such as: TTC/4TC/MTC, the down-averaged coin is still going to happen in both open screen and DISC'd patterns. Two-Tone Conductive or Multi-Conductive will not respond with iron audio though (in Open screen), and this is important. The 29Fe value will respond with a high tone in TTC (26Co -50Co is all High Tone no matter the Fe value in TTC, and high tone from 39Co-50Co in 4TC).

What is the point of all this? In fields of iron nails and iron junk when hunting for non-ferrous targets - don't use DISC unless you need it to silence wrap-around high-tone blips from pointy/bent elongated iron (you'd DISC out only near 01-02Fe in this case). Let the CTX speak.

Now iron nails will respond with a high tone too in TTC/4TC/MTC but interestingly when non-ferrous coins are affected by close proximity to iron the Co-value wanders up the scale (or jumps up). That means the 11-38 penny will jump to 20-41, 28-44, 30-45, etc., the more iron is averaged into the coil swath. Unless the iron is flat and large (to be sufficiently conductive) it is only the coin that has that signature. So, in fields of iron you are not worried about the TID Fe-value, it will probably be very high (high iron, like 28Fe+). You are looking for the Co-value that is in the high conductive range. That is your coin amongst iron trying to let you know it is there (if you are aware you will answer its call by digging it up).

Yes, all the tones in TTC/4TC/MTC will be variations of High-tone, even the nails. But in 4TC/MTC the high-tones will be differentiated more because the audio is Med-Tone for Co-values 26Co-38Co, where iron lives. So, best use 4TC or MTC and look for the deep coins in iron that still register High-tones and don't bother worrying about how high the Fe values are, they don't matter in this case.

Note: If you have the E-Trac instead of the CTX, the perpendicular nail reacts similarly. Your cursor will be down-averaged too and the audio will disappear if you've DISC'd out the high Fe values (which is commonly done to silence iron). You won't get the red-cursor that the CTX gives you, the TID cursor just goes away with the E-Trac in iron. There is a slight difference between the E-Trac and CTX: with DISC being used to silence iron the E-Trac nulls (no audio) a bit sooner than the CTX as the nail approaches the coin. It's a small difference.

For both detectors when using the same DISC'd patterns just realize that the audio is going to be gone (silent) for any coin-iron combo in real soil conditions where the coin is deeper than say 2", which is most of the time with older coins. If you are listening for the High-tone sound with DISC set - you probably aren't going to hear anything. You won't know you missed that sliver coin at 6" either because it had no audio report.

The larger difference is that the E-Trac TID cursor is gone almost immediately (when <3" apart) whereas the CTX keeps the TID cursor jumping about (in the DISC'd area), even when the nail is placed on top of the coin. Being able to follow the cursor into the DISC'd areas was an improvement over the E-Trac, but the E-Trac can be setup without DISC and you've solved that problem.

Moral of the story ... don't use DISC'd iron settings when looking for coins around nails. You'll lose the audio tone in TTF/4TF and lose the TID cursor (E-Trac) or only have the red-cursor (CTX) to guide you, which isn't good. Use 4TC or Multi-tone Conductive and you'll get the High-Tone audio (if no iron DISC used) and you'll get the TID cursor on the screen. Just look for the higher conductive Co-values as that is likely your non-ferrous conductive target (coin) in the iron fields (and try and ignore the Fe-value - they don't mean the target can't also be a coin).

-Johnnyanglo

 

[kittlitz]

Now that was a post! Thanks for the info, Johnnyanglo. I wish there were a way to bookmark posts on this forum.

-Ken

 

[metalpopper]

But the ctx (and other detectors) do 'make that zone silent' !

What you're not understanding, is the practicalities of metal detectors, and the 'dynamics...realities...physics.....call it what you may' of how metal detectors work.

Any detector, when swept over the ground, sees soil, cowsh?t, and coins etc.

At every sampling-second of the electronics's acquisition, it produces a number relative to the SUM of what it is seeing; but that sum is a progressive sequence of measurements.....

Imagine a target, of stationary value 10....you sweep towards...over...and past it.

It then acquires a sequence of samples...2, 4, 7, 10, 10, 6, 5, 3.....

Now the circuitry 'integrates' those samples...sums them, I.e. = 47.

It shows the resulting vdi and blob on the screen at point related to the peak 10.

Now you block out 10.....but that's not the 'full picture'.....so you still will hear those 'elements' not suppressed by just 10.

So a zone of silence needs to be 'wider' (numerically) to improve its effectiveness.

The drawback to that, is it detracts from the audio produced by numerically adjacent targets etc.

So what I'm trying to say, is that you can/do silence a 'number', but targets are made up of many numbers....of which only two are shown.....hence the iron-mask method as compared to individual cell method of tackling iron discrimination.

The subject could fill a book.....my attempt here is but a 'comma's' worth.

Matt.

 

[metalpopper]

Spot on explanation Larry......Matt