Category Archives: metal detectors

Diver uses JW Fishers PT-1 pinpointing magnetometer to locate buried steel plates and beams. Inset: Steel beam found with PT-1 magnetometer.

Engineers & Archaeologists
Use Marine Magnetometers

Diver uses JW Fishers PT-1 pinpointing magnetometer to locate buried steel plates and beams. Inset: Steel beam found with PT-1 magnetometer. 

  Oceanographic engineers and marine archaeologists are among a broad range of users employing magnetometers in their underwater search, salvage, and construction operations. Magnetometers are super sensitive instruments that detect iron and steel at a much greater distance than conventional metal detectors. These devices assist in array of tasks which include; hunting for shipwrecks and artifacts, locating and tracking deeply buried pipelines, looking for lost tools and equipment, tracking down weapons and explosives, pinpointing the position of anchors and moorings, finding sunken vessels and submerged vehicles, and much more.      Q & S Engineering, based in San Diego, provides consulting and engineering services in the environmental, geotechnical, and oceanographic fields. Their core specialties are site assessment and remediation, marine sediment and groundwater investigations, marine ecology and biology studies, and geophysical surveys using side scan, multibeam, and high resolution seismic sonars. Recently Q & S was contracted to assist in a Latin American project involving the deconstruction of a large steel pier. One of the job requirements was; all steel, surface and subsurface, must be removed from the area. Since the pier was old and in a state of disintegration, pieces had fallen off and become imbedded in the ocean bottom and under the beach sand. Q & S engineer Conrad Leslie contacted JW Fishers Mfg, a company specializing in underwater search equipment, to determine which tool would be best to locate the missing pieces. A conventional magnetometer was not an option because its extreme sensitivity would make it difficult to pinpoint individual pieces in close proximity to the huge steel pier. Underwater metal detectors were ruled out as their limited range would not allow them to detect the metal parts if they were buried deep in the sand. The device recommended for the job was the PT-1 pinpointing magnetometer.  This instrument was powerful enough to detect pieces of steel buried up to 16 feet in the bottom, yet could also isolate single small pieces even when close to larger ones. Leslie reported, “Unfortunately bad weather during the two week period we were there restricted diving operations, but when  the weather let up divers searched the area from the beach as far as they could safely walk with a 5 foot surf. The PT-1 proved very effective in locating buried steel sheets and beams, and even those close to the pilings. The whole team was very impressed with how well the magnetometer performed.”    Another group having success with the pinpointing mag is North Carolina’s Department of Cultural Resources (NCDCR). The agency was established in the early 1970s with a varied mission that includes preserving the state’s historical and cultural resources. Nathan Henry, Assistant State Archaeologist and Conservator, reports the Underwater Archaeology Branch is currently involved in a high profile project mapping and excavating the wreck site of Blackbeard’s flagship, Queen Anne’s Revenge. One of the instruments the team is employing is the PT-1. The magnetometer’s ability to pinpoint artifacts in areas strewn with many iron and steel targets is a key advantage in this environment.  It is the ideal tool to locate all of the ferrous objects on the site including anchors and chains, cannons, cannon balls, ship’s stoves, and iron hardware used in construction of the vessel.  The first anchor from the Queen Anne’s Revenge has already been raised from the muddy bottom where it had by laying for the last 300 years.    Global Infrastructure LLC provides offshore and inland subsurface services for the energy industry including inspection, construction, maintenance, and repair using multipurpose vessels, diving systems and ROVs. One of the areas in which they specialize is pipe cleaning and repair. Facilities from offshore oil rigs to inland gas companies rely on their piping systems. Typically these systems extend over many miles and run under oceans, lakes, and rivers. Before a line can be serviced, it must first be located. Often the exact position of these lines is not well known and finding them can be a time consuming task. In addition, it is not unusual to have several lines running along the same path. To assist in quickly finding and pinpointing them, Global has acquired a PT-1. “The magnetometer works well and makes the job of tracking these pipes much faster and easier”, reports project manager Adam Vandenhouten.     A few of the many other organizations using Fishers magnetometers are Algosaibi Diving and Marine Services in Saudi Arabia, Indiana University Office of Underwater Science, Gray Diving Services in Australia, Great Lakes Exploration Group, Cosmos Agencia Maritima in Peru, DUC Diving in Holland, University of West Florida Archaeology Institute, Alpha Logistics in Tanzania, Bekk Solutions in Hong Kong, and Weber Marine in Louisiana.          

 

Fishers PT-1 pinpointing magnetometer

The PT-1 pinpointing magnetometer is the ideal tool for iron pipelines and steel armored cables. The PT-1 has both audio and visual readouts. Included in the kit are land and underwater earphones, along with AC & DC battery chargers. The rechargeable batteries power the PT-1 for 15 continuous hours.  Hard carry case is optional.   The PT-1 not only tracks pipes and cables, it will also locate anchors, chains, dredge heads, weapons, explosive devices and any other ferrous metal object within its detection range.

PI (Pulse Induction) versus VLF (Very Low Frequency) SAND SHARK versus TIGER SHARK

Underwater Detectors

by Rusty Henry, Service Manager

PI (Pulse Induction) versus VLF (Very Low Frequency)
SAND SHARK versus TIGER SHARK
 

Maybe the title of this article should just be SALT WATER VERSUS FRESH WATER! The problem with that, however, is its very seldom a “cut and dry” decision.

The obvious answer, if money were no objective, is to own both a SAND SHARK and a TIGER SHARK and have the best of both worlds. However, I know what it’s like to have to buy tires and groceries and pay bills at the same time, so I am going to try to help any perspective customers to narrow their choice down to a single machine.

The more obvious advantage of the TIGER SHARK is its increased versatility due to its superb discriminate mode.

Even though the SAND SHARK is strictly an all-metal detector, it has a distinct advantage around (or in) salt water due to its superior stability.

However, I have seen guys do remarkably well with the Stingrays and Tiger Sharks at the ocean and on the other hand, some PI users (by ignoring the blip-blip signals of nails, wire, hair pins, etc.) can still clean up at a fresh water lake!

Before making a decision based strictly on salt water searching versus fresh water (or land) searching, perhaps we should look at some of the more subtle differences between Pulse Induction (SAND SHARK) versus VLF (TIGER SHARK).

The first thing that comes to mind is the ability of a VLF machine to respond to tinier metal objects than the PI is capable of. Therefore, if finding very fine gold chains, or perhaps a gold stud from pierced earrings or a tiny little gold charm from a charm bracelet is a high priority, then you are definitely leaning toward the TIGER SHARK.

Before jumping to a final decision based on that, let’s consider the area you might be searching for these items. If you live in the Midwest, where there are many fresh water lakes and the only time you have an opportunity to search at the ocean is on an occasional vacation, then your decision is an easy one—the TIGER SHARK. But what if you live right on, or very near, the ocean and have the opportunity to search there often, especially down in the wet sand at low tide and especially after a good storm.

When it comes to working successfully down in the wet sand at the ocean, the new SALT WATER MODE of the TIGER SHARK can significantly improve its performance in that area. However, it still can’t compare to the stability (and consequently – success) of the SAND SHARK when searching down near (and especially in) the salt water. This is because wet salt is conductive and a VLF unit which transmits from one set of windings and receives from another is adversely affected. The PI unit which “pulses” and receives from the same set of windings is not affected by conductive salts or mineralization.

Even though the SAND SHARK is not capable of competing for the absolute tiniest of metal targets (especially with the 10½” coil) any normal-sized ring or other piece of jewelry is no problem. Certainly this also includes all coins, but we all know that “coins are just something to keep you interested while you’re looking for the next piece of jewelry.” Also, keep in mind that before Tesoro’s original Stingray VLF, no one was finding fine gold chains with an underwater unit anyway.

To carry this one step further, how much good is it for the TIGER SHARK to respond to even tinier metal targets, if when working in or near the salt water there is so much noise from the conductive salts that these targets get masked out? You can always lower the sensitivity of the VLF models to get more stability but then that will cause losses as well due to loss in depth.

Another way of putting this is that the PI unit may appear to have less depth and sensitivity initially, but when you consider that it is able to retain all of this through all types of ground and conductive salts, the end result is many times an increase in depth overall when compared to the VLF in these adverse conditions.

I have found very small, thin (pinkie finger and birthstone-type) rings down in the wet sand at low tide with my SAND SHARK and many items that I know I would have not found if trying to control a VLF unit in that environment. I have even used a Pulse Induction-type unit successfully in a gold nugget searching situation taking advantage of the fact that it is not bothered by the otherwise troublesome mineralization, but I’ll admit that I did not find any matchhead-sized nuggets or smaller…only about pea-sized (about 1 dwt.) and larger.

The added weight and clumsiness of an underwater metal detector as compared to good top performing lightweight land-based units has never made using an underwater detector that attractive to me for either nugget hunting or coinshooting. Most detectorists will opt for a good lightweight (and usually less expensive) model for the land hunting or searching in the dry sand “blanket area” on the beach and use their underwater unit primarily in the water. But, if you have been considering a submersible metal detector, I will say that whether it be a Pulse Induction or Very Low Frequency unit, an underwater detector is the easiest detector there is to pay for over and over in finds. The TIGER SHARK would definitely come closest to being an “all-around” detector and the obvious choice away from the ocean. However, for extended salt water use, I simply have to recommend the more specialized SAND SHARK.

It is my sincere desire that anyone, after reading this article, will not be disappointed with their choice of either of these units and be happy and successful taking advantage of the strong points of that respective underwater detector.

Can You Choose the Right Detector? Tesoro Metal Detectors

Can You Choose The Right Detector?

by Jack Gifford

 

Many articles have been written on “How to choose the right detector.” Some of them seem designed to steer you into a particular detector that may not be right for you. Most are genuine attempts to explain how to pick your “right” detector. It’s very easy for a potential metal detector buyer to become confused by all the contrasting claims made in advertisements and catalogs. If this buyer also happens to be new to the hobby of treasure hunting, his task of choosing the right detector to suit his needs can be very difficult indeed. Many would-be TH’ers end up buying an instrument that is poorly suited to their needs because a friend has the same kind or because a dealer prefers selling that model or for a variety of other reasons. For the most part, this can be avoided if the buyer takes a little time to “sort things out” before he makes his purchase.

It is doubtful to me that there really is just one “right” detector for you. There are many good brands on the market, and there could be any number of detectors that would satisfy your needs and budget. It seems more important to avoid buying the “wrong” detector—one which is unsuitable for your needs. The process of avoiding the “wrong” detector is much the same as many articles have outlined for choosing the “right” detector but with a little different emphasis on some points.

The experienced TH’er who has been active in the hobby is much less likely to purchase a detector that doesn’t fill his needs than the first time buyer. The reason is simple; he has more knowledge of the industry, the terminology, the manufacturers, and the state of the art. The first time buyer can lessen his chances of buying “wrong” by being patient and by learning some of the things the experienced hunter already knows.

Don’t be in a hurry to buy, even if you have a chance to pick up “a real bargain.” I was introduced to an older gentleman several years ago, who, as soon as he found out I was in the metal detector business, began to tell me about the bargain he just picked up. “It’s real big, has three coils, and a suitcase to carry it all in. I got it all for only $250,” he said. Then he asked “That’s a pretty good deal, isn’t it?” When I questioned him, he didn’t know whether it was a BFO or TR, didn’t know if it discriminated or not, and didn’t even know if it worked. Turns out, he could have bought a then modern TR Discriminator for the same price he paid for a “dinosaur” (an extinct species). I didn’t have the heart to tell him the truth because he was so proud, so I just said, “Sounds like a heck of a deal to me.”

Any prospective TH’er wants to get a “beeper” and “get out there.” Avoid the urge to buy until you are ready. Take the time to find the answers to at least these three questions before you even consider buying a detector: 1) What kind of hunting will you be doing and where? 2) What type of machine fits these needs? and 3) What is the price range of such machines? Honest answers to these questions will take some research and learning on your part, but it will put you on almost equal footing with the experienced TH’er, and more important, it will be fun.

To learn the answers to these important questions, you will need to pursue many sources of information. The most honest source of information will be the magazines dedicated to the treasure hunting hobby. These magazines cannot afford to cater to one manufacturer’s interest because they would lose the advertising revenues of the other manufacturers. There are many good books on the market which I would consider “generic” but there are also many others which, while containing some basically good information, may also heavily push a particular brand. In fact, some metal detector companies own or have a vested interest in publishing companies which print treasure-oriented books. If it appears that a book is favoring a particular brand, be aware that you are reading a sales brochure. Most cities have a treasure hunting club, and this can be a super source of information since most treasure hunters love to talk about their hobby. Most independent dealers can also provide answers to your questions and can be another valuable aid to you.

While we don’t intend to give you a “check the box” guide to answering these important questions, a brief word about each is in order. Firstly, you must determine whether you would prefer coinshooting, relic or cache hunting, nugget hunting, or prospecting. You must also determine the feasibility of this type hunting in your locale. Hunting Civil War relics in Mississippi makes a great deal of sense, but what if you live in Montana? Your locale will also have much to do with your next question because of its mineralization level. Perhaps you live in a high mineral location but will use your detector only on your vacations in Florida where the mineralization is low.

Once you have determined your most likely treasure hunting style and location, you are ready to determine the proper detector type to use. Your choices are basically these: 1) General Purpose VLF/TR/Motion Discriminator, 2) Nugget Hunting VLF/TR, 3) Nugget Hunting VLF/TR/Motion Discriminator, 4) Pulse, 5) Two Box TR, and 6) Waterproof Detector. You will have to determine the type best suited for your needs, but that is pretty easy to do. The General Purpose detector pretty much does it all, but it doesn’t have the gain and stability to do an effective job of serious nugget hunting. A good VLF/TR Nugget Hunter does a good job at nugget hunting but is worthless as a coin shooter without a discriminate mode. A Pulse detector cannot discriminate but is hard to beat on a salt water beach. The 2 Box TR can only find very large caches or mineral veins but can do so at extreme depths. And while waterproof detectors make underwater hunting easy, they are typically much heavier than land based detectors. You will need to determine which type is most suitable for your needs.

Finally, once you choose a detector type that will fill your needs, you are ready to determine how much you should spend. Many “How to Buy the Right Detector” stories have stressed very early to set your spending limit and not to exceed it. I believe this approach is a very good way to increase your chances of buying the “wrong” detector. If your treasure hunting preference is coin-shooting for the old ones in the parks of Lake Tahoe or Colorado Springs, you are going to need a motion discriminator. Motion discriminators are complex and expensive, but many companies build their top of the line models with bells and whistles which are not truly necessary. Why pay $800 and up for a detector that can’t do anymore for you than one which may cost only $400. By the same token, if you only plan to use your detector at the beach on your yearly vacations and mostly to “give the kids something to do,” why spend $500 for a detector when a $189 Compadre is more than you need? Spend the extra $321 on Mama. She’ll love you for it. Or if prospecting is your game, the extra cost of a nugget hunting detector is going to be necessary.

Check the price ranges of the various manufacturers’ models for detectors that will fulfill your requirements. Determine what features are available and what they cost. Then see if you can narrow your choice to a particular price range that will give you the performance you NEED and the features you WANT.

Remember that no matter what type or brand detector you eventually choose, you will need to spend a lot of time with it to really get the best performance from it. The amount of time you plan to spend using your detector should play a large part in your budgetary considerations. If it’s a vacation toy, don’t spend any more than necessary. If it’s an every weekend obsession, get the best unit you can afford.

Now you are ready to get serious about selecting some particular models from the many manufacturers for some serious consideration. By now, you can probably judge whether a “bargain” in a used detector is really a bargain or not since you should know how to judge whether it meets your needs. Again the time and money you have spent reading the treasure hunting magazines has been a good investment, because now you have a pretty good idea of who the significant manufacturers are, and you may already have a “gut feel” for who “means business” and who “blows smoke.” If not, that’s the next order of business.

All manufacturers like to think they build the finest metal detectors, and they aren’t bashful about saying so, myself included. Most of the detectors from the major companies are good, but how can they all be “the finest”? Deciding which brand to purchase is not easy because all you usually see is the marketing razzle-dazzle. Slogans are easy to think up, claims are easy to make, and promises are easy to break.

You need to get beyond the claims and mottoes in the advertisements and try to determine if the detectors are capable of meeting your needs. Send for catalogs or data sheets from all the manufacturers that you feel you may be interested in. These catalogs are also sales tools, just like the ads, but they should have more technical information than the ads. Try to compare the manufacturers’ models that meet your needs and price range. List their similarities and differences. This will help you determine if you really have confidence that these particular models are for you.

Now you need to compare the units you feel confident about. If you have a local dealer, perhaps you can try them all in person. If not, do not automatically eliminate those that you can’t try yourself. Remember, also, that your local dealer may just push the unit he likes best or makes the most money from, so don’t hurry and don’t be hurried. If there is no local dealer where you can see a unit, ask the manufacturers for additional information about the particular models you are interested in. Ask them questions about their detectors and how they will meet your requirements.

Compare the product reports in the magazines for the detector you are interested in. These reports can be very helpful if you judge them properly. Do they make original, meaningful statements about the product or does the report borrow heavily from the manufacturers’ buzz words and phrases? Do they say how well the detector works, or do they tell you how to work it? You can tell from the way the report is written whether the detector was really impressive or just adequate.

Compare the manufacturers’ willingness to answer your questions, compare dealer recommendations, compare what others are using in your area, and compare the technical content of the manufacturers’ furnished materials. By now, you will probably find yourself tending to favor one particular brand or model over the others. Be patient just a little longer, though and learn all you can about the particular model you favor. If you are counting heavily on the recommendations of a friend or dealer, do they use this model for the same hunting conditions that you intend to use it for? Is this model designed for the task? Is it an up-to-date design? Is it versatile enough to adapt to other uses if your hunting preferences change?

Now that you are reasonably settled on a particular detector, you need to decide where you will purchase it. This seems like a small point, but you should be just as confident of your dealer as you are of your detector. A good local dealer will answer all your questions before and after the sale, he will show you how to use your detector, and he can provide you with a lot of helpful information about treasure hunting in your area. They will check out your machine when you take delivery, and some even do a little service work for minor problems or furnish loaners if you need to return your detector to the factory. However, just because he is local doesn’t mean he will provide these services or even that he is knowledgeable about detectors. Check him out.

If you don’t have a local dealer, some of the larger mail order houses offer a trade-up plan in case you are dissatisfied. Since they can’t offer the personal service of a local dealer, they generally discount their prices somewhat. Some manufacturers will retail from the factory if they don’t have a dealer close to you, but don’t expect them to discount. To do so would alienate their dealers and would be corporate suicide.

Decide how your interests would best be served and choose a dealer that you feel comfortable with. Satisfy yourself that you can rely on your dealer after the sale as well as before.

Now, after you have purchased your “beeper,” don’t expect instant success. Read and study the instruction manual and work with your unit as much as possible. Regardless of the brand or model you have chosen, it will require patience and work on your part to fully understand what your detector is telling you and to achieve the results that it is capable of. When it does “all come together,” it will prove to have been more than worth the effort.

Metal Detector Terms Part ii

Faint Signal: A sound characteristic of metal detector targets that are sometimes deeply buried or very small in size.

False Signal: An erroneous signal created by over shoot, ground voids or highly mineralized hot rocks. See also Back-Reading.

Faraday-Shield: A metal foil wrapping of the searchcoil windings or metallically painted searchcoil housing interior for the purpose of eliminating electrostatic interference caused by wet vegetation.

Ferrous: Descriptive of any iron or iron bearing material.

Ferrous Oxide: An oxidized particle of iron which generally becomes nonconductive and makes up the natural negative ground mineral matrix. Hematite, which is also iron oxide (Fe203) will respond as positive or metallic. See also Black Sand.

Frequency: The number of complete alternating current cycles produced by the transmit oscillator per second. Measured in cycles per second. VLF Very Low Frequency = 3 to 30 kHz; LF Low Frequency = 30 to 300 kHz;MF Medium Frequency = 300 to 3000 kHz; HF High Frequency = 3 to 30 MHz.

Frequency Shift: A feature which suppresses the audio interference (cross-talk) between two detectors using identical transmit frequencies in close proximity.

DetectionNet Metal Detectors

Eddy Currents: Small circulating currents produced on the surface of metal by the transmitted electromagnetic field. These currents then produce a secondary electromagnetic field which is then detected by the search coil receiver windings resulting in inductive imbalance between the windings.

Electromagnetic Field: An invisible force extending from top and bottom of the searchcoil created by the flow of alternating oscillator frequency current around the transmit winding. See also Detection Pattern.

Electronic Pinpointing: An automated detuning feature which narrows signal response for the purpose of target pinpointing.

Elliptical Coil: A searchcoil with an ellipse shape. This coil can be either concentric or widescan type.

Ground Balance: A state of operation using specialized circuitry to ignore the masking effect that iron ground minerals have over metal targets.

Ground Balance – Factory Preset: A feature which eliminates the manual ground balance control and its adjustment from the operator’s setup procedure. This adjustment is performed internally by the factory to optimize operation over an average range of nonconductive soils.

Ground Balance – Manual Adjusted: A feature requiring a manual control adjustment procedure to neutralize the effects of negative minerals in the search matrix.

Ground Balance – Self Adjusting: A feature which senses change in ground mineral content and continuously readjusts the ground balance while in operation. Sometimes called Ground Tracking or Automatic Ground Balance.

Ground Filter: Complex circuitry found in motion-type detectors which separates mineral signal from the metal signal allowing it to be further processed by the discrimination circuitry.

Matrix: Refers to the total volume of ground penetrated by the transmitted electromagnetic field, which may contain varying amounts and combinations of minerals, metals, salts and moisture.

Metal: Metallic substances such as iron, foil, nickel, aluminum, gold, brass, lead, copper, silver, etc.

Metal Detectorist: A person operating a metal detector in the field. This name is preferred by many over Treasure Hunter.

Meter: A detector component that provides visual information to aid in target identification. Meters feature either an LCD or needle indicator which may display intensity of signal, target depth, target identification, type of metal, or battery condition.

Mineral-Free Discriminator: Any metal detector that can reject or ignore trash metals while simultaneously balancing ground mineralization.

Mineralized Ground: Any soil that contains conductive or nonconductive components.

Mode: A condition of operation, selected by the operator, for specific desired function(s).

Motion Discriminator: A detector type that requires searchcoil motion to activate its simultaneous ground balance and discriminate functions. See also Mineral-Free Discriminator and VLF/TR.

Hand Held: A metal detector configuration whereby the operator holds a shaft or handle which supports the searchcoil and control housing. Also called pole mount.

Head: See Searchcoil.

Hz or Hertz: Cycles per second. See also Frequency.

Hip Mount: See Body Mount.

Hot Rock: A rock which contains a higher concentration of nonconductive ground minerals than the surrounding matrix to which the detector is balanced. A metallic (positive) response will be heard in the motion and non-motion modes and a null or negative drop in threshold is heard in the all-metal, ground balance mode over these rocks.

Isolator: A nonmetal stem which attaches the searchcoil to the control shaft eliminating metallic interference in the detection pattern. On some detectors, the entire lower shaft is made of a nonmetal substance.

kHz or Kilohertz: 1000 cycles per second. See also Frequency.

LCD or Liquid Crystal Display: Used on a metal detector as a graphic visual indicator same as a meter/needle indicator.

LED or Light Emitting Diode: A semiconductor which produces an illuminated visual response.

Loop: See Searchcoil.

 

Metal Detector Terms Part i

Metal Detecting Terms. metal detector Coin Depth Indicator: A visual indicator used in conjunction with calibrated circuitry to indicate depth of buried coins in inches or millimeters.

Concentric: A metal detector searchcoil configuration using one or more transmit and one receive windings having unequal diameters aligned on a common center; most recently arranged on the same plane and called coplanar concentric.

Conductive Salts: One of the major mineral types which make up the positive ground matrix. Wet, ocean-salt sand produces a positive rise or metallic type response on an air tuned threshold.

Conductivity: The measure of a metal target’s ability to allow eddy current generation on its surface.

Control Housing: A metal or plastic box which holds circuit boards, indicators, meter, controls and power supply.

Convertible/Combination: A metal detector configuration allowing versatility in operator handling, i.e., hand held to body mount.

Coplanar: Any searchcoil configuration in which transmit and receive windings occupy the same level or plane.

Crystal Controlled Oscillator: A transmit oscillator employing a crystal to maintain stable output frequency.

Depth Penetration: The greatest measure of metal detector’sability to transmit an electromagnetic field into the soil matrix and produce a target signal.

Detection Pattern: The densest or strongest region of the searchcoil’s electromagnetic field where detection occurs. Its shape is balloon and changes in size directly proportional to target surface area.

Detuning: Adjusting the audio threshold into the null or less sensitivity tuning zone. Also a method of narrowing a target signal width manually for precise pinpointing. This is accomplished by retuning to audio threshold over the target response area.

DISC: See Discrimination.

Discrimination: Adjustable circuitry which ignores or nulls audio responses from a specific conductivity range allowing positive responses to be heard from metals higher in conductivity above the discriminate control setting. Designed primarily to eliminate audio response from trash metals. See also Motion Discriminator.

Double Blip: A signal characteristic common to elongated ferrous targets such as nails or coins lying close to the surface detected in the All Metal no-motion mode.

Double D or 2 D: See Wide Scan.

Drift: A loss of threshold tuning stability caused by temperature change, battery condition, ground mineral content or detector design.

Air Test: A test performed by moving various sized metal samples beneath the metal detector searchcoil to check the detector’s features and target response. This test is not an accurate indicator of ground depth penetration capability.

Alkaline: A type of battery able to sustain longer periods of current drain with greater storage life when compared to the standard carbon-zinc type.

All Metal: Any operating mode or control setting which allows total acceptance of any type of metal targets. Usually associated with the Ground Balance mode.

Audio ID: See Tone ID.

Audio Response: See Target Response.

Auto Tune: Circuitry which continuously retunes the detector’s threshold to the initial manually tuned audio level. The retuning rate following target rejection or drift can be preset or variable.

Back Reading: A false signal, when operating in the discriminate mode, caused by a rejected target coming within one inch of or contacting the searchcoil bottom.

Bench Test: An air test to determine at what approximate discriminate settings various metal samples are rejected or accepted. The test is conducted in a non- metallic area.

Black Sand: One of the most extreme components of nonconductive, negative ground minerals. Also called magnetite (Fe304) or magnetic iron oxide.

Body Mount: A configuration whereby the control housing is separated from the control shaft and fastened to the operator’s body lessening arm fatigue and expanding usability for shallow water hunting. Also known as hip mount.

Cache: Any intentionally buried or secret hoard of valuables.

Carbon-Zinc: The most common standard dry cell battery type.

Coil: See Searchcoil.

Metal Detector Terms Part iii

Neutral Ground: Soil that has no nonconductive or conductive mineral properties. Lacks mineralization using a metal detector.

No-Motion: Refers to any mode of operation that does not require searchcoil motion to trigger target response. Also called non-motion.

Notch Accept: Operation whereby all target responses are “tuned-out” except those the instrument is adjusted to accept in the notch “window.”

Narrow Response: A target that produces an audio response so short that pinpointing is almost not needed.

Negative Ground: Soil that contains non-conductive minerals which have a negative or nulling effect on an air-tuned threshold.

Ni-Cad or Nickel-Cadmium: A rechargeable type of battery cell.

Non-Ferrous: Not of iron. Metals of the precious class (i.e., gold, silver, copper, etc.)

Notch Discrimination: Filtering circuitry which allows a “window” of desirable targets to be accepted within the entire rejection range of unaccepted targets, i.e., rejecting nails, foil and pulltabs while accepting nickels and gold rings of the same conductivity. This circuitry can also be adjusted to reject all metal targets while accepting only a specific conductivity range.

 

Notch Width: A finite discrimination range of target conductivities (“window”) at the chosen notch level.

Null: The zone just below audible threshold in metal detector tuning. This also refers to the momentary drop or quiet response of threshold sound as the searchcoil passes over a discriminated or rejected target.

Notch Level: A control used to select the target level or target conductivity which the notch filter will act upon.

Notch Reject: Operation whereby all targets within the notch width at chosen notch level will be “tuned-out.”

Overlap: The amount of searchcoil swing advance not greater than the searchcoil’s physical diameter.

Overshoot: A common false signal heard as the searchcoil passes over a rejected target when using a no-motion All Metal mode in conjunction with automatic retuning. Excessive tuning restoration pushes the audio above threshold level creating a positive response at the edges of target detection periphery.

Phase Response: The length of time between eddy current generation sustained on a metal’s surface and the resultant secondary electromagnetic field effect on the searchcoil’s receive winding. Related to target conductivity.

Pinpointing: Finding the exact target location with respect to a searchcoil’s designated center. Accomplished by interpreting the centers of audio response width in perpendicular directions or scans. See also Detuning.

Positive Ground: Soil which contains conductive minerals or moist salts which have a positive or upward effect on an air-tuned threshold.

PI or Pulse Induction: A mode of operation where the transmitter circuit pulses an electrical current into the ground be fore it quickly shuts down. The eddy cur rents dissipate immediately from poor conductors such as wet salt sand and ground minerals. Metals hold eddy cur rents because they are better conductors. When the receiver circuit comes on, it picks up the returning signal from metal; the eddy currents in the ground minerals have already disappeared.

Quick Response: A short time period between metal sensing and peak audio/ visual indicator indication usually associated with all frequency ranges of TR detectors.

Rejection: An indication of target nonacceptance by a null in threshold or broken sound while operating in a discriminate mode.

RF-Two Box: A radio frequency detector having its own transmit and receive windings separate and in an orthogonal configuration. This detector is capable of deep large object detection while naturally ignoring small targets such as nails and individual coins.

Scan: Refers to 1) the effective searchcoil detection width or 2) searchcoil movement over the ground.

Scrubbing: The searchcoil is pressed and held in contact with the ground while searching to maintain even audio threshold. With newer detectors, this technique is used to gain depth.

Searchcoil: A circular (or other shaped) plastic housing containing single or multiple transmit and receive windings (wire coils) in a specific configuration. A searchcoil emits and receives signals from the ground and metal targets. Also called loop, coil or head.

Searchcoil Cable: An electrostatically shielded cable of conductors (wires) which convey signals to and from the searchcoil and control housing.

Sensitivity: The capacity of a metal detector to perceive changes in conductivity within the detection pattern. Generally, the more sensitivity a detector can smoothly provide, the more depth it will achieve in sensing targets.

Signal: An audio response or visual indication alerting the operator that a target has been detected.

Signal Width: The total distance of ground an audio signal is sustained during search- coil travel or scan.

Silent Search: Refers to detectors capable of producing a target signal while operating below the threshold audio. Also called silent operation.

Scuff Cover: A protective cover for the searchcoil bottom. Also called coil cover or skid plate.

Slow Motion: A description of searchcoil speed required to operate the motion discriminate mode.

Stability: The ability of a metal detector to maintain manually adjusted tuning thresh- old under the effects of outside interference. See also Drift.

Surface Area: Refers to the area of a target closest to the searchcoil where eddy current generation can take place.

Surface Mount: The art of mounting electronic components on the surface of a printed circuit board rather than using the “through board” method. This allows more technology in a much smaller space and with much higher tolerances.

Sweep: The motion employed in moving the searchcoil across the ground.

Target: Refers to any object that causes an audio or visual response in a detector.

Target Masking: When large sizes or high concentrations of trash metals drive the threshold into the null zone suppressing weaker, positive responses from deeper or smaller targets.

Threshold: Continuous tone that establishes a reference point for tuning the detector to ground balance it. The threshold tone also establishes the minimum sound level for deep targets in the discriminate mode.

Tone ID: Circuitry producing different audio tones for each target’s conductivity range, i.e., low tone for nickel, high tone for coins.

Ten-Turn: A control which can be manually rotated ten times to cover the full electrical range of the function. Usually associated with tuning or ground balance function.

Test Garden: A mapped plot of buried targets at various depths to aid in learning characteristic target responses and in comparing metal detector performances under a given ground mineral content. Also called test plot or test bed.

TH’er,TH’ing: Universal word contractions for treasure hunter and treasure hunting. Also known as Metal Detectorist.

TR or Transmitter-Receiver: Term describing method of operation of early detectors. Some manufacturers still produce this type of detector. Electromagnetic field distortion caused by mineralized ground interferes with depth penetration as this type of detector does not ground compensate. It does balance conductive salt water effects so, it is primarily used in salt water and on low mineral salt water beaches or low mineral inland locations.

VLF/TR: A class of detector that can operate in both the All Metal, Ground Balance mode and the No-Motion Discriminate, Non-Ground Balance mode.

Wide Response: A target that produces an audio signal over an area wider than the searchcoil diameter.

Wide Scan: A coplanar searchcoil with two “D” shaped transmit and receive windings positioned back to back and overlapping. This searchcoil type is capable of detecting a target across at least its full diameter. Also called Double-D or 2-D.

Zero Discrimination: Used to describe detectorswhose discrimination control allows the acceptance of all metals at zero setting.

Visual ID: A feature in which a visual indication is produced to help identify the target.

Visual Indicator: A meter, LCD or LED that signals a target’s presence.

VLF or Very Low Frequency: See Frequency.

VLF/DISC: Term associated with detectors capable of mineral-free operation in both the Discriminate and All Metal modes.

Key Features of Garrett Ace 250 Metal Detector and Specs

Garrett Ace 250 metal detector important Features
Specifications:

Target ID Cursor Segments     12
Iron Discrimination Segments    2
Accept Reject Discrimination? YES
Search Modes: 5 + Pinpoint
Sensitivity Depth Adjustments 8
Electronic Pinpointing YES
Frequency 6.5 kHz
Audio Tone ID Levels 3
Standard Searchcoil 6.5″ x 9″  PROformance
Length (Adjustable) 42″ to 51″ (1.06m – 1.29m)
Total Weight 2.7 lbs. (1.2 kg)
Batteries 4 AA
Warranty 2 Year  Limited Parts/Labor
  • Interchangeable ACE series searchcoils are available
  • Expanded Target ID Legend: easy-to-read above large LCD screen
  • Pushbutton Controls: with One-Touch operation
  • Electronic Pinpointing: to precisely locate target and speed  recovery
  • Accept/Reject Discrimination: to modify  discrimination patterns
  • 5 Search Modes: select pre-set discrimination pattern or create your own
  • Continuous Coin Depth Indicator: to determine target depth
  • Battery Condition Indicator: shows battery life continually
  • Other features: 3-piece travel/storage, disassembles to 24″; adjustablearm cuff; quarter-inch (1/4″) size headphone jack.

Search Modes (Discrimination Patterns): 5 plus electronic pinpointing

  • All Metal (Zero)
  • Jewelry
  • Custom
  • Relics
  • Coins
  • Pinpoint

Garrett ACE 250 Metal Detector

metal detector faqs

Frequently Asked metal detector Questions

1. How do I pinpoint a target?Slowly and methodically sweep your searchcoil from side to side, keeping it one to two inches above the surface. Overlap each sweep by advancing the searchcoil by about one quarter to one half of its diameter. Scanning in a straight line helps to keep the searchcoil level and the overlap sweeps uniformly while reducing the likelihood of lifting the searchcoil after each sweep. Listen for a peak in the audio sound. Hold the searchcoil one to two inches off the ground and slowly sweep it back and forth in an X pattern. Note where the sound becomes the loudest. The target should be located in the center of the imaginary X. Many of today’s modern metal detectors are equipped with an electronic pinpoint button. Read your owner’s manual for complete electronic pinpointing instructions.

2. At what depths can a detector find treasure?It’s impossible to predict with complete certainty how deep a specific detector can be expected to find metal. This is because there are a variety of factors that affect a detector’s performance. For example, the amount of minerals in the soil, the type of metal that’s being detected and the quality of the detector itself impact how deep your metal detector will hunt. The size and surface area of a target also affects metal detection. For example, the larger a metal target, the easier and more deeply it can be detected.Using a searchcoil larger in diameter can also help a detector achieve greater depth. A 12.5” searchcoil produces a more extensive magnetic field that penetrates the ground more deeply to find objects at depths that a smaller size searchcoil can’t reach.

3. What do I need to know about my detector’s batteries? NiCads  and nickel metal hydrides are rechargeable batteries that last between 8 and 12 hours and cost up to 10 dollars each. Alkalines are disposable batteries that last between 25 and 30 hours and cost about two dollars each. Because extreme temperatures can drain battery power, it is recommended that you always carry a spare set of batteries. In cold weather, attaching the battery pack to your belt under your jacket can help keep batteries warm and dry.

4. What is discrimination?Discrimination refers to a metal detector’s ability to reject a target, such as a pull tab and foil or accept a target such as a coin or piece of jewelry based on its metallic composition. With features like Target Imaging and Tone ID, your detector can tell you what your target is before you ever dig.

5. What is True Size?

True size is obtained in  much the same way as true depth. Multiple receivers, within a GTI metal detector, add additional dimensions of target ID, not just material ID. Ultimately, however, it;s how multiple receivers relate to one another that provides these true measurements, not just merely having them. True size and depth are Garrett exclusive features and are only possible with  Garrett GTI detectors, which were designed to give treasure hunters the most accurate information about a target before they dig.

6. Is overall depth compromised when searching with discrimination?

Yes. To achieve the greatest depths when searching for large, cache sized-objects, many professionals hunt in the All-Metal mode and use a large searchcoil.

7. What is the significance of a detector’s Operating Frequency?

A metal detector transmits magnetic energy into the ground and senses distortion in the magnetic field due to the presence of a metal object. The frequency content, temporal form and amplitude of this magnetic energy can affect detection capabilities and overall performance characteristics. There are two primary detection technologies used in today´s metal detectors: Single Frequency (also known as Continuous Wave) and Multiple Frequency (e.g. Pulse Induction and Dual Frequency). Each technology has its own detection characteristics, understanding these will enable you to choose the right detector for your treasure hunting needs.

8. Do I really need headphones when treasure hunting?For maximum success and privacy when treasure hunting you should use headphones. They are essential in noisy areas and enhance audio perception by bringing the sound directly into your ears.

9. Do I need more than the one searchcoil?The searchcoil is a vital part of your metal detector. It is the flat, typically circular disk, which generates a magnetic field and senses metallic targets in the surrounding environment. It is located at the end of the stem and is connected to the control housing via a cable that is wound around the stem. The size, depth and energy output (power) of the magnetic field is determined by the shape and size of the searchcoil. Understanding the purposes behind the various sizes and shapes of searchcoils will empower you with the ability to choose the best searchcoil for the right application. For a detailed explanation of the types and benefits of optional searchcoils read our Searchcoil site.

10. Are there online forums or treasure clubs I can join?There are countless online forums where treasure hunters share their own tips, help other hobbyists with their detector, and of course, show off their latest treasure. You can also contact your local dealer, he or she can point you towards all the exciting clubs and events that other treasure hunters are hosting right in your own backyard!.

 

11. Are there any laws surrounding treasure hunting?Every square inch of property in the United States is owned — by an individual, group, corporation, governmental body, etc. And, there are definitely laws that have been written to apply to various treasure hunting situations. Each state has its own statutes concerning where you can and cannot search and whether you may keep the treasure you find. You must learn these laws, and remember that they can be changed at any time.

How Search Coils Work, and what types they are.

HOW SEARCH COILS OPERATE Searchcoils generally consist of two internal sets of coiled wires, a Transmit Coil (TX) and a Receive Coil (RX). Mono coils can be different in that one coil acts as both the TX and the RX. When the detector is turned on, the TX coil generates a magnetic field in the surrounding space.When a metallic object is within this generated magnetic field, it will create a distortion in the magnetic field. The RX coil will sense this distortion and send a signal to the control housing.

DetectionNet Metal Detectors Here

The searchcoil is a vital part of your metal detector. It is the flat, typically circular disk, which generates a magnetic field and senses metallic targets in the surrounding environment. It is located at the end of the stem and is connected to the control housing via a cable normally wound around the stem. The size and depth of the magnetic field is determined by the shape and size of the searchcoil. Understanding the purposes behind the various sizes and shapes of searchcoils will empower you with the ability to choose the best searchcoil for each application.

A searchcoil’s detection pattern is determined by the combination of the TX’s generated field pattern and the RX’s sensing field pattern.

SEARCHCOIL DEPTH The detection depth of a searchcoil, as a rule-of-thumb, will be approximately equal to its diameter, for a coin-sized object. However, as a searchcoil’s size increases and its field pattern becomes larger, the field pattern becomes less concentrated and begins to miss small objects. For a coin-sized object, this effect becomes noticeable when using searchcoils larger than about 15” in diameter. Since the field generated by a large searchcoil is larger, deeper and less concentrated than a small searchcoil, it is the best choice when hunting for targets that are usually large and deeply buried, such as caches or relics.

SIZES & SHAPES

There are a variety of searchcoil sizes and shapes. The correct one to use depends on the environment it will be used in as well as the targets being sought. A change in any one of these variables may require a different searchcoil.

Generally, searchcoils are circular or elliptical in shape. An elliptical searchcoil is more maneuverable than a circular searchcoil and its narrow width actually provides greater coverage than a circular coil due to its elongated length. However, a circular searchcoil has slightly more detection depth and sensitivity in non-mineralized soil, so it is still the most commonly used shape. Searchcoils also come in a 2-box configuration, which are used for detecting deeply buried targets.

Searchcoils range in diameter from a few inches to several feet. Those less than 6” in diameter are generally considered small, 6-11” in diameter are considered medium and over 11” are considered large. As noted earlier, there is a direct relationship between the size of a magnetic field and the size of a coil. The bigger the coil, the larger the magnetic field. Therefore, larger searchcoils generally detect deeper than smaller searchcoils.

Small Searchcoils

Because the magnetic field of a small searchcoil is concentrated within a small volume, it is the best choice for hunting in areas with a lot of metal debris. This allows you to maneuver through and around trash to locate good targets, especially when searching in tight places where large searchcoils cannot go. In addition, because of their concentrated detection field, small searchcoils are the best for detecting very small objects. However, a small searchcoil provides less coverage per sweep; more scans will be required to cover a search area.

2-Box

In a 2-box configuration, the TX and RX coils are physically several feet apart. This configuration provides a lightweight, manageable means of achieving the performance of a 3′ to 4′ diameter searchcoil. Because of its large size, and consequently large detection field, the 2-box is the best choice for detecting large, deeply buried objects such as relics and caches. Also, because of its large detection field, it ignores objects smaller than about 3″ in diameter. This characteristic is advantageous when hunting in areas heavily littered with small trash objects.

There’s also an enhanced version of the 2-box, only available from Garrett. It is the Treasure Hound with Eagle-Eye pinpointing. This version incorporates an additional pinpointing coil for precise target location.

Medium Searchcoils

For general-purpose hunting, which typically includes coins and coin-sized targets, a medium sized searchcoil (8 – 9”) is the best choice. Because a medium sized searchcoil provides the best combination of magnetic field concentration, detection depth and capability to detect the greatest range of target sizes within the detection area, it is standard with most detectors. In addition, it’s lightweight and easy to maneuver.

Large Searchcoils

Large searchcoils generate wider and deeper magnetic fields than small coils and consequently provide greater depth and coverage. This means that scanning a search area requires fewer sweeps with a large searchcoil than with a smaller coil. This larger scan area, however, can become a problem in trashy areas where the searchcoil is metal detecting several targets at once.

CONFIGURATIONS

In addition to searchcoil sizes and shapes, there are also a variety of searchcoil configurations available, with each proving to be the best choice depending on hunting applications and ground conditions. The configuration of a searchcoil refers to the arrangement of the TX and RX coils within the searchcoil shell. There are basically five configurations: Concentric, Mono, Imaging, Double-D and 2-box.
Concentric Searchcoil

Concentric

The concentric configuration consists of a TX coil and RX coil which are usually circular and arranged as shown at left. The advantage of this configuration is that both the TX and RX coils are wound as large as possible within a given searchcoil diameter. This provides the largest possible detection field and greatest detection depth, making the concentric coil potentially the most sensitive configuration available.

In addition, concentric coils also provide the most symmetrical detection field, allowing ease in pinpointing and consistency in target identification. For these reasons, they are the most commonly used searchcoil and will provide the best overall performance in most environments.

Unfortunately, this configuration is the most susceptible to interference from ground minerals, which results in substantial loss of performance when used over heavily mineralized ground.

Mono  A mono-coil is available only on Pulse Induction detectors and is a variation of the concentric configuration. The mono-coil can be manufactured with the TX and RX coils located together or as a single coil acting as both TX and RX.The detection and performance characteristics of the mono are essentially the same as the concentric in that it provides the maximum possible sensitivity, but suffers some performance in mineralized ground.

Imaging

An Imaging searchcoil is an enhanced version of the concentric configuration that features an additional RX coil. This extra coil provides the detector with additional target information necessary for true target-depth perception and true target-sizing capabilities.With this additional sizing information, the detector can more fully characterize a target and for the first time distinguish between trash and good targets of the same conductivity (e.g. a quarter vs. a soda can). Only Garrett’s GTI series offers this technology; no other detector in the world has this capability.

The Double-D configuration is designed to significantly reduce ground interference and, thereby, recover the performance lost by a concentric coil over mineralized soil. With the Double-D, it is the arrangement of the TX and RX coils that produce a canceling effect of ground signals.This configuration is called DD because both TX and RX coils are in the shape of a “D”. The positive detection field of the DD runs beneath the overlapping center section from front-to-back. The remaining portion of the coil actually produces negative (i.e. canceling) detection fields. It is this canceling field that allows the DD coil to maintain performance over mineralized ground.Because of its small positive detection field, the DD is inherently less sensitive than a concentric searchcoil of the same size, over non-mineralized ground. The Double-D will, however, significantly outperform the concentric coil over mineralized ground. For this reason, it is highly recommended when hunting over mineralized ground commonly found when prospecting and relic hunting.

code of ethics for metal detector users

Metal Detector users Code of Ethics

You are responsible when it comes to using your metal detector. you must follow the rules and law and be very careful in its details. We must keep metal detecting and enjoyable hobby for metal detector user, as well as to anybody else.

Never trespass. Always obtain permission prior to entering private property, mineral claims, or underwater salvage leases.Always check federal, state, county and local laws before searching. It is your responsibility to “know the law.”Abide by all laws, ordinances or regulations that may govern your search or the area you will be in.Never litter. Always pack out what you take in, and remove all trash dug in your search. Do not damage, deface, destroy, or vandalize any property (including: ghost towns and deserted structures), and never tamper with any equipment at the site.Do not build fires, camp or park in non-designated or restricted areas. Fill all holes, regardless how remote the location, and never dig in a way that will damage, be damaging to, or kill any vegetation.Never contaminate wells, creeks, or any other water supplies.Leave all gates and other accesses to land as found. Be courteous, considerate, and thoughtful at all times.Uphold all finders, search and salvage agreements. Promote responsible historical research and artifact recovery, and the sharing of knowledge with others.Report the discovery of any items of historic significance to the local historical society or proper authorities.

You can enjoy your treasure hunting and metal detecting hobby, however make it pleasant for everyone, by following the rules and law.