Metal Detecting Blog

Review of the Garrett AT Gold for Relic Hunting in Georgia

Tue, 17 Jan 2012 17:49:14 -0800

The Garrett AT Gold Metal Detector for Relic Hunting. Watch Video of this hunt below

After receiving my Garrett AT Gold detector just before Christmas 2011, I quickly went to an area where it has the hottest ground I can find in Oregon that only Pulse Induction detectors work well on. The AT Gold performed better there than my Garrett Scorpion and did better in Discriminate mode than in all metal. Now knowing the limit of my AT Gold on crazy hot iron infested ground I was ready to test it on some Civil War Relic Hunts in Georgia on my Christmas visit there.

I went to several of my usual spots near the Battle of Gilgal Church which still yielded some nice relics in the past. As targets were getting scarce I had plenty of time to see how the Garrett AT Gold performed in the hot Georgia red clay. Although this ground was not as hot as ground I have encountered in California and Oregon it did have its hot pockets to contend with. I found with the Fast Track ground balance function worked quite well and fast at the press of a button and about 4 pumps of the coil it was done!

I did this fairly frequently in the changing ground where this Battle and encampments took place. The ground ranged on the VDI scale from a low of 35 to a high of 84. I also came across pockets of large pieces of quartz rock atop of a hill where a Confederate trench was constructed which contained a good deal of iron minerals which set off the detector. As per my test in Oregon revealed, I set the AT Gold in Disc mode and scanned the quartz rock and got no signal telling me that the quartz were hot rocks. I know that there were no gold in this quartz as there is no history of placer or load gold in that particular area plus I had tested it years ago with mortar and pestle.

Now knowing that the AT Gold performed very well in Georgia while hunting almost exclusively in the all metal mode except testing hot rocks in disc mode, I had more confidence to find those small and missed relics from previous hunts. And on my first swing at site number 2 I found 3 percussion caps in a square yard area just about 15 feet from getting out of my car. In this previous site I had found a US button from a soldiers uniform, I had high hopes for more. However I did not find anymore of those but I did find several more percussion caps as well as a few shot bullets and a small pistol bullet. No target was deeper than 4-5 inches.

Perhaps the reason I found so many percussion caps using the AT Gold this trip might be because they are small and made from brass and are low conductors, which makes it ideal to find them using the higher frequency of the Garrett AT Gold, operating at 18 kHz. It sure did bang on them hard and with crisp audio. A detector operating at 7 kHz or lower and in the discriminate mode might have missed these small caps or signaled them as iron, hence the possibly of them not being dug previously.

My settings on the AT Gold that I used varied as I was testing the machine on as many possibilities I could come up with. I usually hunted in the all metal mode sensitivity at 7 of 8. Threshold at 00-05. I tested with iron audio on and off and it worked well, but must one must get use to it as a small low conductive item can "sound" like iron, you must sometimes look at the meter to tell you what VDI number it shows. If it shows a higher number than you have set as your highest number for the iron audio then it is possibly not iron even though you might here the slight iron grunt as it still might be within the 1-40 iron range. It is good to dig all targets to get used to what the iron audio is telling you for your first few hunts, then you will more confident later to judge whether the target is worth digging as per what the AT Gold is telling you.

Regarding the Ground Balance Window feature while Relic hunting I found it to smooth out the small pockets of hotter red clay that are present while scanning without the need to ground balance frequently. I had it set on the stock setting of 2 mostly. It defiantly does work as is useful. I did some further testing on this feature when back in Oregon while nugget hunting and I found that it seems like a disc mode mixed with an all metal mode when engaged. It did seems and bit more noisy as it was trying to adjust to the ground in the window I set it at. I cut it off totally for the first time and it was a bit more stable in ground that is very consistent in it's ground balance settings. It operated like a normal VLF without the window feature.

I did find my first gold nugget on that trip and it was the smallest nugget I had ever found at, I'm guessing, a .05 grams, Unfortunately I dropped the nugget while trying to get it out of my camera bag to show my buddy, it went back into the river it came from. Oh well…more nugget hunting reviews of the AT Gold coming in the future. I did not get to totally submerge to AT Gold in the river to test out it's full water proof to 10 feet feature, but I did get it wet a bit and had no problems at all. I was quite confident being around the river while detecting with it.

In conclusion, I found the Garrett AT Gold a pleasure to use while Relic Hunting and it was light enough to swing all day long. It is a very deep machine from what I can tell, the ground balance features work as they should and I never had a problem with the ground being to hot to hunt in as the detector had all the adjustments necessary to deal with it. I finally found my favorite high frequency metal detectors for Relics and Nuggets.

Try one out folks, If you like the Garrett AT Pro, the AT Gold, having a true all metal mode, is a fantastic member of the Garrett AT Series detectors.

Tags: Garrett AT Gold for Relic Hunting, Best Metal Detector for Relic Hunting, Garrett AT Gold Review, Mashdetectors for Relic Hunting

Watch the video below of me using the Garrett AT Gold in Georgia during a Relic Hunt

The New Garrett Gold Prospecting Metal Detector - AT Gold

Sun, 4 Sep 2011 23:10:38 -0700

By: Alan Mash

The long awaited new gold prospecting metal detector from Garrett is here! The AT Gold!

I have been waiting for Garrett to update its Scorpion Gold Stinger for awhile now and they have done it with a bang. The is in the new family of detectors, the AT detectors. (All Terrain).
This machine is in compliment to the new AT Pro that Garrett released last year.

Here are the specifications of this new Nugget Hunting Metal Detector:

• Target ID Cursor Segments - 20
• Iron Discrimination Segments - 40
• Search Modes - 3
• Sensitivity/Depth Adjustments - 8
• Electronic Pinpointing - Yes
• Frequency - 18 kHz
• Audio Tone ID Levels - 3
• Standard Searchcoil - 5" x 8" ( 14x20cm) DD PROformance
• Length (Adjustable) - 42" to 51" (1.06m - 1.29m)
• Total Weight - 3.03 lbs. (1.4 kgs.)
• Batteries - 4 AA (included)
• Warranty - 2 Year, Limited Parts/Labor

The AT Gold operates at 18 khz for high sensitivity to very small gold nuggets. One of the new exclusive features Garrett has built into the machine is the Ground Balance Window. If a detector ground balances at a certain number such as 65, the AT Gold balances in a broad window. Example is when the AT Gold ground balances at 65, it actually ground balances at a minus 2 AND a positive 2. So the entire ground balance window will be from 63-67 at the same time. This results in less ground balancing and less noise from iron pockets that were outside the normal 65 balancing.

Another key feature for electronic prospectors is the high resolution iron audio which is the same as the AT Pro with its 40 segments of discrimination, but an added feature is the low tone iron grunt while operating in the threshold based deep seeking all metal mode.

While hunting and you come across an iron nail it will alert you with an iron grunt audio as well as a target ID number, so you can move on to the next target. The more ground you cover the more likely you will find a gold nugget.

One of the best features of the AT line of metal detectors is its water proof to 10 feet depth. This will open up an entire new area for prospectors looking for some of those out of reach gold nuggets that only could have been reached in the past by the Infinium LS for gold prospecting machines.

Other beach or water machines could give it a try but the AT Gold’s high sensitivity will beat these other water proof machines to the small gold as well as the Infinium’s sensitivity compared to regular beach/water detectors. Quite a combo punch on gold nuggets with those two detectors for finding gold. A water proof Pulse Induction detector and a 18 khz water proof VLF...that’s what I’ll be using in the gold fields!

I will have my hands on an AT Gold very soon and I will give it a work-over in the goldfields and release a review for the AT Gold, hopefully with some new gold nuggets in my poke. Stay tuned folks, It appears Garret has put out a winner here...time to show the gold!

UPDATE Dec 2011: I now have my hands on the new Garrett AT Gold and so far I am very impressed with it. I’ll just say this, it is VERY sensitive to small gold nuggets! How small? I can pick up some of my .05 gram gold nuggets with it at about 2+ inches with the nuggets sitting on top of hot mineralized soil...stay tuned; I’ll have full reviews up soon with video after I take it out in the field!

Update January 2012: I now have online an article review of the Garrett AT Gold while Relic Hunting in Georgia accompanied by a video of the event. So far the AT Gold is a very powerful Relic detector and while utilizing the iron audio grunt in all metal it was a pleasure to use to sniff out those unwanted iron targets. Read more here...

Tags: Review Garrett AT Gold for prospecting nugget hunting for gold nuggets Gold Prospecting Metal Detector

The Best Metal Detector for Coin Hunting Ever Designed: The Garrett GTI 1500

Tue, 31 May 2011 22:20:20 -0700

By: Alan Mash

Why is the Garrett GTI 1500 the best metal detector for finding coins in the world? It is simple, because of the Imaging features. Imaging and Imaging, a Garrett exclusive. Other wise known as Treasure Vision.

It has been around awhile actually...since 1997. It also is in the Garrett GTI 2500 which this machine differers from the 1500 in that it has an All Metal Mode. It is a little heavier than the 1500 which why I say it is better than the 2500 for coin hunting although they are identical in the discrimination mode.

Why is the Imaging so important in coin hunting? It has 5 different sizes in its display after hitting a target. Most coin sizes are size B. Sometimes you will hit a coin spill and the multiple coins will size larger than B, but as you know these targets must be investigated as they will register in the upper scale of any machine as far as conductivity is concerned.

See the size graph on the detector screen on the right...it is color coded and black pixels will show up inside the color graph when a target is hit. If the target is size E, pixels will fill all sizes indicating it is a size E target. The graphics on the top of the display show target evaluation as to what it might be. If you hit a size C target, look up at the graphics list and also the target conductivity. If you get a C size target and its conductivity displays an 8, then you most likely have a screw-cap.

As you see from the graph all coins will be size B. Want some coins? Dig all size B targets. A 12 oz can will most of the time be a size D and conductivity around 8.5 - 9 on the GTA scale. (graphic target analyzer scale) A coin popping beast this Garrett GTI 1500 is.

How deep will it detect a coin? With the stock 9.5 Imaging coil it will detect at respectable depths. I have found on both the 1500 and the 2500 that I crank the sensitivity up to around 10.5-11 (12 max) you will get better depth but can be unstable around a lot of electrical interference. A smoother operation set the sensitivity to around 6 - 7 out of 12 with almost an insignificant loss of depth.

Put the 12.5” Imaging coil on this machine and you will get another 2.5 - 3 inches + of depth and the Imaging is deadly on this coil. With this coil expect depths close to MInelab’s universal metal detectors like the Explorer and Safari. They come stock with an 11”DD coil and multi-frequency and cost twice as much as the GTI 1500. Stock machine to stock machine the Minelab’s will beat this 1500 on depth. To equal the playing field add the big 12.5” Imaging coil and go at it. You won’t be disappointed. But the Minelab’s do not have Imaging, enough said.

Whites V3 has a type of sizing feature that seems to work ok. I’d have to say if I had a choice for coin hunting however the Imaging of the 1500 vs the size feature of the V3, I’ll take it any day over the Whites. Why? The Garrett is easier to use, another Garrett exclusive on all their metal detectors.
The White’s V3 is a wallet numbing $1800.

The Whites is a great machine, but is very complicated. Kind of like Windows vs a Mac. Macs are easier and more user friendly. Both work. But I’ll get better results with less headaches and I will spend less money with the Garrett GTI 1500. And dig just size B targets? How easy is that?

A coin hunting metal detector at its finest the Garrett GTI 1500. It is what it was designed to do!

To see the GTI 1500’s little cousin, which has Profiling technology, click here: Garrett GTP 1350. It will show the size profile of a target, which not as detailed as the 1500, but it also is a coin magnet.

Tags: garrett GTI 1500 coin hunting imaging coins coin shooting best coin detector finding coins best metal detector for finding coins. best metal detector for coins best coin hunting detector

Review of the Garrett Infinium for Hunting Gold Nuggets

Tue, 15 Mar 2011 20:56:25 -0700

By: Alan Mash

The Garrett Infinium is a pulse induction (PI) metal detector and differs greatly from the standard VLF machine that is more frequent and abundant in the metal detecting industry. It is unique because the iron mineralization that it comes across is mostly ignored. Just the fact that pulse induction in general has this ability already puts you ahead of the game when you search for gold nuggets.

A standard VLF (very low frequency) detector itself can be built for the gold fields are still very noisy in hot iron infested soil, even if it has an aggressive ground tracking circuitry. When I started with the Infinium for the nugget game, I noticed a huge difference in my ability and mental process as my ears were not bombarded by ground noise through my headphones which lead me to detect longer. Being able to detect longer also increased my odds of coming across some gold nuggets that my detector will respond to.

I detected one day for 6 hours before I stumbled upon on a 1/4 oz gold nugget. My body was tired as I walked a few miles while working the area with my machine, but my ears and my mind still sharp after detecting that long, hearing just a nice emerging tone that never wavered as the Infinium came upon a nice piece of gold. That was refreshing as my switch to pulse induction seemed to be paying off.

My Infinium handled every bit of hot iron infested ground mineralization that it came accross. A VLF machine is so affected by these extreme minerals that you might not hear the nugget under the coil as it could just be ground noise or it could be a desirable target. It can be hard to discern sometimes with a lot of audio signals coming at you in the headphones with a VLF. It can be done with many hours of practice, but a pulse induction detector cuts the learning curve time down a bit so you can concentrate on the terrain features and looking for gold.

Equipped with mono coils the Infinium LS (land and sea) has handled the hot soil very well and I rarely needed to remove them and switch back the DD coils, the DD’s handle hot ground a bit better, but are little less sensitive to small gold nuggets. When I do I use the DD coils, it was for old mine shaft walls looking for ore veins or small pockets of gold left behind by the past miners who dug the tunnels.

This machine is very powerful and has great depth at targets from about one gram in size and larger. Smaller gold are still detectable, but depth is lost, since the elements are very small. My smallest piece of gold was .3 grams at 1.5 inches and another piece weighing .4 gram at 2.5 inches depth. As you can see the Infinium snags these little nuggets, but other manufacturers of metal detectors such as the Minelab GPX Pulse Induction series machines will pick sub .1 gram gold nuggets. But you will pay $5000 for these machines. If you are on a budget, the Infinium is the detector for you.

I paid $1062 for my Garrett Infinium and I paid for it with gold nuggets from Northern California in 3 months with it. I would say that if I give a percentage of increasing my chances for finding these rare minerals in nature by switching to pulse induction, and with the Infinium in particular, I would say a 50% increase in odds over a VLF machine in finding gold nuggets.

The Garrett Infinium is a great bang for the buck while using it for electronic prospecting. Gold is usually found with a lot of iron near or around it. This machine will help you more easily to find it in its alluvial and elluvial form and even if you come across it in its natural state as in the pocket or vein, this machine will sniff it out.

Tags: How is the Garrett Infinium for Prospecting Garrett Infinium for Nugget Hunting

Metal Detector Field Test & Review - The Garrett AT Pro

Sat, 5 Feb 2011 19:14:08 -0800

By Chris Gholson

Anyone that has been involved with metal detecting for any length of time will have undoubtedly heard the name Garrett. Garrett has done wonderful things for the industry in four decades by supplying quality detectors and through their efforts to help promote the hobby. Garrett products have been responsible for finding millions of dollars worth of ancient coins, relics, jewelry and gold nuggets, and are revered by treasure seekers.In addition to the hand-held products, Garrett produces a range of detectors for use in security screening, crime scene investigation and for military de-mining operations.
One of the newest additions to their consumer line is a detector known as the AT Pro. The Garrett AT Pro is a VLF detector, which operates at approximately 15 kHz and is outfitted with a waterproof 8.5" x 11" elliptical Double-D coil. The machine weighs in at roughly 3.2 pounds and is powered by four AA batteries. It features an updated panel with an LCD screen and all pushbutton controls.But what really sets this machine apart is its versatility. It is a true multi-purpose detector that has the ability to locate all types of buried treasure-coins, relics or gold. And with its unique All-Terrain design, this machine can be used just about anywhere.The entire detector can be submerged under water to a depth of 10 feet! With this level of weatherproofing, the ATPro is an excellent choice for streams, ponds, or in shallow water.The ATP includes Garrett’s exclusive Target ID technology and patented discrimination features. It offers six detection modes, which can be adjusted using the MODE button-three STANDARD and three PRO.
The Standard detection modes include: Custom, Coins and Zero. The Pro modes also include: Custom, Coins and Zero.The difference between the Standard and Pro modes has to do primarily with a target’s audio response. In all three Standard modes, the detector provides a full-strength binary audio response regardless of the target’s size or distance from the coil. In other words, while hunting in any of the Standard modes, the detector will make a beep when passed over a metal target. The pitch will vary depending on the conductive properties of the target, but it will be just a beep.The Standard modes offer quieter, more stable operation and may be a good place for new users to start while familiarizing themselves with the detector.However, to truly unlock the power of the ATPro, the user will want to explore the Pro modes.
The benefits of these modes include the ability to hear and determine a target’s approximate size and depth via the Proportional Audio and Tone Roll Audio.Pro mode also offers faster recovery speeds for separating targets that are in close proximity. The advanced audio features of Pro mode are intended for skilled users who wish to hear the signature of targets versus the simpler target response provided in Standard. Basically, the Pro mode will allow you to hear targets as they really are.For example, if there is a coin near the surface, the detector will produce a loud signal response. If we take that coin and bury it at six inches, the signal produced will be weaker, thereby telling the operator that the target is a reasonable distance away from the coil. Whereas in the Standard mode, the detector will give the same type of signal response whether the coin is near the surface deeper.As mentioned, there are six operating modes to choose from. The ZERO Mode is essentially an All-Metal mode. There will be no discrimination and all metals will be detected.
This is a good option for relatively clean, trash-free ground.The COINS mode can be used to find most types of coins and jewelry, while eliminating many trash targets like iron and foil. In this mode, the discrimination level has been preset to 35 and one notch that is associated with foil has been excluded. Pull-tabs have not been eliminated because they have properties similar to small coins and jewelry. This mode will be a good choice for those that like to hunt parks, playgrounds, or perhaps along the beach.The CUSTOM mode has been left open for the user to customize.
The factory preset for this mode is the same as ZERO. Any changes or adjustments made in CUSTOM will be retained after the detector has been switched off. Changes made to the ZERO or COINS modes will not be retained.The Digital Target ID system found on the ATP provides a specific value to help the user identify targets more accurately. Unknown targets are identified in the LCD with a number. This number is a representation of the target’s conductive properties. Numbers closer to 1 are the most ferrous; numbers closer to 99 are the most conductive. The Digital target ID number can be used in conjunction with the Target ID Cursor, which is found just beneath the Target ID Legend.The Target ID Cursor will move along the Target ID Legend and settle on the place that best represents the target found. Ferrous targets show up on the left half, non-ferrous targets that are lower in conductivity will show in the middle, and highly conductive targets will show on the right half. The Digital Target ID is more precise than the Target ID Cursor, however, when used together, it is fairly easy for the operator to get a general idea of what type of target has been detected.
Another way for the operator to quickly determine the probable identity of a target is by listening to the audio tone. The ATPro is equipped with a Tone ID feature that produces three distinct tones based on a target’s composition and conductivity. Low tones indicate ferrous items, such as nails, wire, boot tacks, etc. Medium tones indicate small or thin non-ferrous items. Including gold nuggets, foil, small jewelry, and some hammered coins. High tones indicate non-ferrous targets with medium to high conductivity, such as most coins and larger jewelry.The ATP can be ground balanced manually and automatically.
Ground balancing is a crucial part of detecting and must be done every time the machine is turned on. Sometimes, if conditions are severe, it may be required several times a day. Persons that do not take the time to ground balance will leave good targets behind.The automatic ground balance procedure is quick and was my preferred method. To balance, simply find a clean piece of ground free of metallic targets. Push and hold the GND BAL button while pumping the search coil towards the ground. If the machine is out of balance you will hear a noise when the coil is lowered or pulled away from the ground. Continue to hold the button until there is very little change in audio when the coil is moved. In some cases, the manual setting may achieve a more precise balance, but it is not recommended for new users.
The ATPro has eight sensitivity settings shown on the LCD. I recommend using the highest sensitivity setting, as this will allow smaller and deeper targets to be found. However, the level used will ultimately be determined by the conditions present in the area. High settings can be used when hunting ground with low mineralization and electromagnetic interference (EMI). Lower settings may be required if the ground mineralization is severe, or there are high levels of EMI.If you find the detector is behaving erratically, try re-ground balancing. If this does not alleviate the problem, try lowering the sensitivity. If this still does not solve the problem, you may need to adjust the frequency.
The ATPro has the ability to slightly alter its operating frequency to help combat noise caused by power-lines, other metal detectors, electric fences, etc. There are four slightly different frequencies to choose from. These adjustments are small and will not affect detection performance.As far as discrimination goes, the ATPro has plenty of it. It features a high-resolution iron discrimination adjustment called IRON DISC. This feature is adjustable from 0 to 39. Low settings offer less iron discrimination, while high settings will eliminate more iron.
The user should never apply more discrimination than is necessary; otherwise the detector may mask a good target that is in close proximity to a bit of iron.In addition to the high-res Iron Discrimination, there are also 12 "notches" available This is called Notch Discrimination and can be used to eliminate trash targets. Any combination of these can be switched on or off. We will not discuss them in detail simply because I feel they should be used with caution.
Turning off a notch in the wrong place could cost the user a nice piece of gold. I found this when passing a nugget across the coil and intentionally hitting the ELIMINATE button. When I ran the nugget across again there was no target response - the nugget had been eliminated! For gold prospecting, I would recommend that none of the notches be eliminated. Instead, I found myself relying more on the IRON DISC.
With this I could run at fairly high levels (25-30) with very little risk of ignoring a nugget.In order to test the gold finding capabilities of the ATPro, I took it deep into the mountains of central Arizona. I chose this area because I had found gold there in the past, and because much of the ground was shallow with little trash. I started off in a mid-sized wash that meandered through the hills for nearly a mile with exposed bedrock full of cracks.I opted to start in the Pro Zero mode first. I increased the Sensitivity to its maximum level and began the ground balance procedure. I quickly discovered this setting was too high and could not cope with the abundant black sands and hot rocks.
After dropping the sensitivity to four and re-ground balancing, the ATPro ran smoothly. EMI was not a problem, so there was no need to adjust the Frequency.My first target came within five minutes. It produced a medium pitched signal and a Target ID of 40. My excitement grew when I increased the IRON DISC to a 25 and the target still rang true. Fortunately, I didn’t have to dig much of a hole before discovering it was only a .22 bullet. At least I knew all was working well with the unit.The next two targets I found were a bit out of the ordinary for a remote location. I swung the coil upwards towards the bank and got a loud, high-pitched signal. While attempting to pinpoint it, I picked up an equally strong signal about five inches away. Neither was affected by the IRON DISC and both gave high Target IDs, ranging from 75-80.The ATP told me they were coins, but I had a hard time believing there were coins this far from town.
After digging them out I found the ATP had not lied. One was a 1976 penny and the other a 1981 dime.I walked nearly a quarter mile more of the wash and only passed over the occasional target that was obviously iron. These signals gave a low Target ID, usually in the 20’s, and would only trigger a broken signal or no signal at all. I dug a few of them just to be safe and found all were nails or fragments of iron.
I was considering moving to new spot when I received a mellow, but definite signal from a piece of bedrock. It was not strong and I believe if I had been swinging the coil any faster I would have missed it. It gave a medium pitched tone with a Target ID that wavered between 35-40 and was not affected by the discriminator. Things were looking positive, but I knew it could be another bullet.The rock was fractured and it was difficult to determine which crack the signal was coming from, so I made use of the PINPOINT feature. This allowed me to stop the coil directly above the target without losing it.I chipped away until there was nothing left but broken bedrock and sand. Finally, I spotted the source - it was indeed a nugget! Although the piece weighed nearly one gram, and had only been concealed by an inch or so of material, it did not give the strong signal I would have expected. The only explanation I came up with was that it must have been turned on edge.I found the ATP a pleasant machine to hunt with.
Some of its strong points were: easy operation, light weight, automatic ground balance, highly versatile, and extremely weatherproof. The ATP is a true All-Terrain detector that can be used on land, in the water, in the mud, or even snow.I did not have the opportunity to test it underwater, but have been reassured the entire detector can be taken up to 10 feet deep, providing the supplied headphones are not submerged..The new AT Pro is a unique detector with something to offer every hunter. It can be used for all types of detecting and can be taken just about anywhere.At only $699.95, it offers versatility and performance at a reasonable price. It comes with a full 2-Year Warranty and is made right here in the USA. For more information, visit www.garrett.com, or call them at (972) 494-6151. Don’t forget to mention that you read about it in Lost Treasure Magazine!
From page 56 of the March, 2011 issue of Lost Treasure
Copyright © 2011 Lost Treasure, Inc. all rights reserved

Tags: How is the Garrett AT Pro for Beach Surf Relic Hunting Prospecting, Garrett AT Pro Review

Metal Detectors Explained

Sun, 30 Jan 2011 10:25:34 -0800

By Peter Sibierski
Metal detectors are devices specially designed to detect metals that lie deep in the water or ground. When it was invented, it is specifically designed for screening or security purposes and to locate mines. There is a lot of industry which uses metal detectors such as food processing, textiles, pharmaceuticals, chemicals, packaging and plastic industries. It is important to check the foods for metal debris to avoid food poisoning. Those metals debris can be broken down to pieces on the machinery in food processing industry. On the other hand, you may find a lot of people that use metal detectors in hunting for treasures and old coins that are electronically driven. So, you might wonder how this thing work to detect metals that are hidden or how metal detector that is hand held work. So let's take a closer look at these detectors to know how they work.
Metal Detectors: How Do They Work?
Generally, metal detectors work on the fundamental principle that when electric current pass through a loop it will produce a magnetic field. One of the basic parts of a detector is an oscillator; it will produce the alternating current. Magnetic field is produced when an alternating current or electricity pass through the transmittal coil which is present in metal detectors. So, when a metallic object or a conductor is present close to the coil, it will generate a current in the object that will produce another magnetic field on it. There is another coil in the loop that can be found in detectors that is called the receiver coil that can detect magnetic field changes because of the presence of a metal or a metallic object. The latest metal detectors use these technologies; VLF very low frequency PI pulse induction and BFO beat-frequency oscillator. Let us discuss about these technologies:
Very Low Frequency (VLF) Technology
The most common technology used in metal detectors is VLF. There are coils in sets of two which is the receiver and the transmitter coil. The coil where electric current is sent and creates magnetic fields which constantly push down to the ground and pull back is called the transmitter coil. Magnetic field gets generated by the metal detector which reacts in any metallic or conductor that passes on it. When it encounters the object, the electric current and the magnetic field is formed around the conductor.
In reciprocal, the receiver coil is protected from the influence of the magnetic field which the transmitter coil produces and it is only affected by the conductor and /or the metallic object's magnetic field. The electricity that runs on this receiver coil produces a magnetic field that is weak when a conductor gets near the metal detector. In turn the coil will amplify and send the frequency of the electricity that has the same frequency with the magnetic field that comes from the metal to make analysis in the control box. Through this, the metal detector that works on VLF (very low frequency) will be able to determine disparity among the kinds of metals, the depth of the position when being detected.
PI Technology
A single coil is used in the PI technology (pulse induction) that is feasible on both transmitter and receiver. However, it is also possible to use 2 to 3 coils. Metal detector that works in this kind of technology can send a short burst and /or pulse of current in the coil that will generate a shorter magnetic field. In every pulse, the generated magnetic field will reverse the polarity and will eventually collapse. Electrical spike can be created and will last in very short period. When the magnetic field, pulse and spike collapses, a known current called as reflected pulse will occur and into the coil it will run. This reflected pulse can only last in seconds.
The reflected pulse can last in a longer period when a metallic or a conductor will get contact with the metal detector. The reason of this is caused by the opposing magnetic field that is produced by the metal detector. Metal detector is a device that has an integrator which contains a sample circuit that can be monitored closely on every spike. The thing that convert the signal, reads and amplifies will convert the signal into a direct current. The connected audio circuit when getting the right amount of electricity will produce tones that indicate a presence of a metallic object.
BFO Technology
The beat, frequency oscillator is like the VLF (very low frequency) that uses two wire coils. The first coil of the device can be found in the control box, and in the search head lays the second coil. The first coil which can be found in the control box most of the time is smaller compared to the second one in the search head. The two coils on the other hand, stay connected in the oscillator that sends out number of thousand electric pulses per second. When the pulse passes through every coil radio waves can be created and the receiver that can be found in the control box collects them all.
After this you will hear clear tones like the radio wave frequency which is created by the receiver. The current of electricity that is moving in the coil in the search head will create a field of magnet that creates a new field of magnet around the metallic object as the metal detector passes over the metals. The creation of radio waves from the search head coil is being interfered by the magnetic field created by the metallic objects. This produces a change of tone in the receiver this changes can helps in detecting the object in being targeted.
There are certain types of metal detector made through this kind of technology that we can see in our everyday life. These metal detectors can distinguish the difference between objects and know the place that they are in and not just detect the metallic target or objects with electrical conduction. We hope this metal detector article can give you the answer to your common questions with regards to how these machines and mechanism works.
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Tags: Explaining Metal Detectors How Metal Detectors Work

Gold Nugget Hunt in Northern California

Thu, 4 Dec 2008 18:54:32 -0800

Well folks, Dredging season is over in California, as I pulled my dredge out of the Klamath River on Sept. 28th. I found lots of good flood gold most of it fine stuff with some small flakes. But no nuggets....
So since I was done dredging I decided to get out the GTI 2500 and try again to find some nugs, after 12 or so disappointing nugget shooting trips I decided to go far up Thompson creek about 7 miles up in the forest from the Klamath. I knew there was a gold mine up that way.
After parking I walked 1.5 miles before even detecting to find area near the mine which is on private property, so finally saw some diggings and decided to detect while still on BLM land.

Long story short....I FOUND ONE! WOOHOO!
As you see in the first pic, I got a signal in a crack in exposed bedrock that was shooting up out of the creek. It came in at #7 on GTA scale...I got excited, could be a bullet or nugget...figured it would be bullet..but nooo!, it was a 0.6 DWT nug.  First thought in my head was ...finally got one again with a detector...geez that took awhile...ahh but is sweet.
I like to use the 9.5 coil instead of the 10x5” DD coil, it is much noisier and hot rocks drive me nuts but the 10x5” DD coil is not very sensitive to small nuggets unless the detector has a higher frequency. The GTI 2500 probably would have heard this one with the DD coil but anything smaller might not, but it handles hot ground MUCH better.
The crack that I cleaned out with screw driver to locate my target. The nugget was at 4 inches, exactly what the GTI depth scale said it was at size A.

Tags: Hunting for gold nuggets in California

Relic Hunt

Wed, 10 Oct 2007 10:00:43 -0700

These were found near the Battle of Gilgal Church. This was part of the Atlanta campaign of the Union invasion of the South. This was a short but bloody battle of one day. But many days leading up to it for building defences. Not much left at this site but I still seem to get get a few goodies. The 10x14 coil you see in pic help me with the mineralization of the area as my detector was running so smooth with this DD coil, I could crank the sensitivity all the way up. Stay tuned...

Gold Nugget Day in Georgia

Thu, 20 Sep 2007 10:00:26 -0700

I was detecting at an old Gold Mine in Georgia looking for some Gold nuggets. And I didn’t expect to find this beauty. It is 7.2 grams. Just under a 1/4 OZ. of Gold. I found it on the edge of a creek down on bedrock about 5 inches. I have only found one more nugget since then but it is tiny weighing 0.3 grams found at 1/2 inch. Both found with a Garrett GTI 2500.

Stay posted, I hope to find more!