VDI Usefulness

[CanisiusHistGrad]

I'm brand new to metal detecting and have been using a borrowed Whites Prism III. I'd like to do more research before buying a more feature rich detector and would like your input on Whites' VDI. How useful is it to have the VDI displayed as opposed to relying solely on the tone of the target ID? Does anyone rely solely on the VDI to ID their targets? Help out a newb, share your experience.

 

[a4wdguy]

To rely solely on a VDI display to determine whether to dig a target or not would be a poor choice. Likewise, disregarding an input to the target identification equation is crippling yourself unnecessarily.

 

[GoldChaser]

a4wdguy is right on. And it depends on the "tone" you are referring to. Some detectors operate in and/or have an 'all metal' mode that usually just has one 'tone.' That means it is the same frequency but the length, quality and volume of the 'tone' changes depending upon the size, depth, and material make-up of the target. This will help you with identifying the size of the target and may provide a little information around whether it may be a hot rock, cold rock or possibly a rusted item. But it cannot tell lead from gold or aluminum, etc. Now there are some detectors that offer two 'tones' of differing frequencies (like the MXT in Relic mode) that will help differentiate iron from other conductors. And there are other detectors with 6+ 'tones' like the M6 (and MXT in "bug" mode) that have 'tones' of differing frequencies. This will provide even more information regarding the conductivity of the target.
What I am not sure of is if the M6 uses the same software for the tones as it does the VDI calculations. I seem to remember reading somewhere (can't find it now) that they may be two different systems. In any case, VDI numbers can jump around a lot. Deep targets will always show as "95 hot rock". They aren't hot rocks, obviously, so the VDI readout is misleading - you just have to be aware of it. Also, larger targets always show higher VDIs. A 2"x3" piece of rusted iron I dug up had a VDI of around +78 = silver range. Same as large aluminum. I have dug up bent pieces of rusted wire that showed VDIs from about -57 up to +74, depending upon the angle of my sweep, etc.
Sorry for the long winded response, but wanted to explain why the VDI readout can be unreliable, and to try to describe different 'tone' systems. That said, I like it. In my mind, the more information the better, as a4wdguy stated. I have the new SST and really like having the multiple (7) tones along with the VDI. Experience and judgment have to then be employed.

 

[CanisiusHistGrad]

I appreciate that you've taken the time to put together a response. Are the 6+ tones different enough that it would be reasonable to expect a person with some mild to moderate hearing loss to be able to differentiate between them? Mostly I have difficulty filtering out background noise - I would imagine good headphones are a must for me.

 

[GoldChaser]

Yes, good headphones are important. They can even help make up for those with hearing challenges.
And yes, you should be able to tell the tones apart. However, I have good hearing and do not have enough hearing-memory in order to hear a tone and instantly know which conductivity range it represents. I guess over time I could build that up, but for the most part I am just trying to differentiate iron tones (low tones) from the higher range of tones. That said, I am pretty good at differentiating the lowest two (most likely) iron tones and the highest (copper/silver) tone from the rest. It's just the middle four that I can't just hear the tone and know which range that it represents. Please note that I almost exclusively hunt for gold nuggets, so will dig almost everything except when I'm positive it's iron, so I really don't need to differentiate between all those intermediate tones, but just be able to tell them apart from the lowest tones. I can always look down at the screen if I want to get a closer idea of the conductivity reading. My recommendation is to find a good local White's dealer that keeps several of these detectors as demos and go over there and test them out yourself. They should also have some headphones you can test as well. This way you can make sure you are very comfortable with what it is you choose to buy. My dealer has even taken me out to parks to test the detectors on real, long-buried targets and to compare machines. That is why I will always buy from him. He also shares some really good techniques and experience with me. Sure I could probably save a few $'s on an auction site or big box store, but his added-value is well worth it. He has even taken detectors and coils back as trade-ins.

 

[Monte]

unless you learn it and use it, knowing that they can all have some strengths and weaknesses.

You have been using a borrowed Prizm III which has Discrimination 'segments' that also serve as Target ID segments. Target ID, on any make or model detector, will only be accurate if it has sufficient target signal. On the M6 and MXT Pro they show a three-level 'confidence bar' that hints to the TID reliability. A full-height bar suggests a good strong signal and the detector is 'confident' that the TID might be reasonably accurate. A half-height bar means there is less signal for certainty, and a quarter bar just means the signal response is weak and uncertain. This is a helpful function to compliment a Target ID reference as well as a VDI numeric read-out.

Target ID, such as the Prizm III's segmented Disc. reference or the more refined Target ID of an upscale model, such as an M6 or MXT Pro of VX3 (current production) or older discontinued models like the XL Pro or XLT, can be helpful as they will define or suggest a particular target class or range of targets. The VDI (Visual Discrimination Indicator) read-out is a numeric reading that can even better define a particular target, or target range, and be used to indicate how 'tight' the VDI numbers are Vs a more 'spread-out' or jumpy VDI response. Often, the more random VDI readings are from a more inconsistent target, like an iron object or an odd-shaped, multi-metal object. A tight-reading response is usually more associated with a smaller-size and more consistent make-up target, such as a silver dime or copper cent.

You didn't mention Tone ID, but I will add that some models use a Tone ID audio response to help classify some ranges or segments of conductivities. Like Target ID and VDI read-outs, it takes time to learn these functions, but I feel they are helpful. I rely on a VDI numeric read-out far more than I do a Target ID icon. also use Tone ID, of some sort, from time-to-time, but definitely not all the time Tone ID can be helpful, but there are may times when a single-tone audio can provide a much cleaner, cleared audio response than trying to fit in a particular audio tone range.

For example, on my XLT and VX3 I use Tone ID when I am mainly hunting for shallower targets, specifically coins. On the M6 and MXT Pro, there is a Tone ID option that has up to 7 Tones and it can be useful, but I only use it about 5% of the time, and never more than 10% because the single tone audio response is usually better and cleaner sounding, especially on mid-depth to deeper targets. I do use the Iron ID audio in the Relic mode with the MXT Pro, and I also rely on the VDI numeric read-out, but not the TID, just as I don't use the TID in the Con & Jewelry mode. I prefer the versatility of the VDI reading.

The Prizm series was changed to the Coinmaster series a few years back, but I would encourage you to consider an up-line model, and strongly suggest the M6. It provides ample field performance and for typical coin hunting needs, and if you add a 6

 

[CanisiusHistGrad]

The Prizm series was changed to the Coinmaster series a few years back, but I would encourage you to consider an up-line model, and strongly suggest the M6. It provides ample field performance and for typical coin hunting needs, and if you add a 6

 

[OregonGregg]

I believe they have been out 6-7 years now.........but correct me if I am wrong. However, Monte is 100% right when he suggest that you up it a bit and go with a M6. I have a MXT Pro and earlier this year back in June Monte was in my area and got to do a Ghost Town hunt with him. Boy did he teach me a lot of stuff, anyhow he had a new M6 with him and I ended up buying it. What a great machine ( its the MXT less the relic and prospecting modes.) Had I realized what the M6 was I prob would have gotten that instead of my MXT Pro. ( I basically use my MXT Pro the same as my M6) I live in Eastern Oregon and can hit Ghost Towns in ID,OR and NV and I find myself grabbing the M6 now more then the MXT Pro. The Eclipse 5.3 coil stays on 98% of the time. For the hunting I like to do I hardly use the 950. Also if you can find a dealer that gives you a good price on a new one before Aug. 31st You can get the bonus bucks deal and get $100 off towards another coil. See whites web site for details. In the last two weeks with the M6 I have found a Shield Nickel, two V nickels, a merc dime and a barber quarter. I really like the M6. For the Hunting that I like to do, iron/trash infested ghost towns etc the M6 is a great machine for that with the 5.3 coil. I can hear Monte saying it now that "there is no one perfect metal detector" Had they put a backlight on the M6 like the MXT Pro, for what I like to hunt, it would have been darn near perfect.

 

[GoldChaser]

The M6 isn't showing up on the White's website any more. At least my version of the website (western region).

 

[a4wdguy]

It's on the factory's website. One of three detectors available under the "E-series" heading. Here's the link: White's Product page

Here's the direct link to the M6 on White's website: White's M6 - buy it now and get $100 bonus bucks!

 

[GoldChaser]

That's funny. My version of the White's website (again, I'm in the western region) only shows the MXT Pro and the MXT on that same page.
The website also promotes Jimmy's SST, perhaps that's why.

 

[a4wdguy]

Now that you mention it, the SST (which I never looked for) doesn't appear on the site we Easterners have. Who'da thunk they'd be so sneaky?

 

[Nauti]

There is a fundemental problem with both visual and tone id.Each target is assigned both a visual and tone response by the manufacturer under factory conditions.When out in the field where a target can be subject to many variables,the tone and vdi response becomes nothing more than a best guess by the software which is not very accurate.
Unfortunately,and this still holds true even with todays technology,if you want to find more good stuff you have to dig more bad stuff.

 

[kshollywood]

On all detectors the vdi numbers are off the deeper the target. Use tone first, then vdi.

 

[nw1886]

There should be no problem there if you understand it....and after experience, having "your own circuitry" compensate. Every machine on the planet is like this (to some degree) and there is a heck of a lot more to a signal than either "strict" audio or "strict" VDIs'.
You just "know" when it's worth investigating a "half promise" (with either audio or VDI).....and it sure feels good to dig them and have them produce!

 

[Phillip_in_NM]

OK, since we're talking VDI numbers and the M6 is being discussed a lot, I have to ask an unusual question: Does anybody else get weird things happening on their M6 with a vdi of 74? For whatever reason, on some targets (only with a vdi of 74) I will get a solid, unchanging lock on 74, but two distinct tones. This has happened to me probably ten times - almost always with remarkable results. This condition led me to my first trade token, a gold cufflink, a silver and gold pendant and a pewter dragon. 99% of the time I get a vdi of 74, I get one tone and dig a penny, but that 1% where I get the two tones, WOW, I never know what delightful thing will pop out. That's why I NEVER, under any circumstances, pass up a vdi of 74. Anybody else experience anything like this?