FAQ's

Frequently Ask Questions

How deep do metal detectors “look” into the ground to find coins or other targets?

While sweep speed and familiarity with your metal detector are the most important factors that determine how deep an object can be detected, coil size and manufacturer can also be factors. Virtually all modern medal detectors use VLF technology and most have search coils of 8 inches or so, the playing field is pretty level across most metal detectors. The chart below gives a good idea of what to expect.

Nickel Dime sized objects	4 to 8 inches
Quarter Half Dollar sized objects	6 to 12 inches
Fruit jar lid sized objects	8 to 16 inches

Are there specific types of metal detectors, or can one detector find everything I’m looking for?

While there are metal detectors specifically designed for underwater work and gold nugget hunting, most good quality, off-the-shelf metal detectors do a good job with most detection assignments.

Why do some metal detectors have complicated looking displays or controls?

Basically, there are two types of metal detectors – simple, turn-on-and-go or the more complicated, manual-adjustment units. The simpler detectors have a preset ground adjust or an automatic ground adjust. Internal circuitry eliminates the mineral effects of the ground. On the more complicated manual-adjustment units, the ground adjust is be set by the operator. If adjusted correctly, the detection depth can be increased a little. If not adjusted correctly, the results can be a very shallow detection depth. Both types of detector can be very effective.

Why do coils vary in size? Are larger coils better?

For all practical purposes, the coil on the all purpose metal detector is correct in most cases. In extremely littered areas, a smaller coil can detect good targets better, even if they are close to, or covered by bad targets; even though a smaller coil can not search as deep as a larger coil. In clear or litter free areas larger coils are able to detect targets over a wider area and find targets that are a little deeper.

How should I set the discrimination level?

In a word, the lower the better. Setting the discrimination high enough to reject pull-tabs, you will also be eliminating most gold targets. Setting the discrimination high enough to reject iron can mask good targets near or underneath them. A dedicated metal detector enthusiasts will spend more time digging up junk than treasure, but he will also have found more good items.

What is notch discrimination?

If setting the discrimination low so that the metal detector can find almost anything, setting a notch is like setting the discrimination so that the metal detector can detect only one target (a accept notch) or everything but one target (a reject notch). An accept notch can be used successfully if you are looking for a specific item; a known type of ring for example, but that is all the detector will respond to. Setting a reject notch to reject pull-tabs for example, will also cause the detector to ignore any items that are similar to the signal produced by a pull-tab; gold for example. Can you search deeper using notch discrimination?No, there is actually a small loss of depth when using a notch filter, but if adjusted properly, the loss is minimal.

What exactly is target ID?

Since every items produced an different signal; responds at a different level of discrimination, any of the manual-adjustment units can ID an item by simply adjusting the discrimination level until the item disappears. This adjustment of the level of discrimination is done automatically and very rapidly by a target ID metal detector. The target is IDed and displayed. This works well on modern coils, but may ancient coins and other artifacts rejected or shown as junk.

Which is better, fixed or manual ground adjust?

If adjusted very accurately, a manual ground detection system may allow for a slight increase in depth, but an inaccurate ground adjustment may produce horrible results. For most people, a pre-set ground adjust will yield much better results. Sometimes my metal detector finds rocks and tree roots. Why?Assuming the ground adjust is set correctly, the rock my you found my indeed be a true positive; it may be iron ore or magnetite. As for the tree root, it may have absorbed chemicals that cause it to be electrically conductive. All you can do is accept the reading and go on. Can an ID detector accurately identify items at any detectable depth? To detect a target, only a reference signal is needed. In order to identify a target, a more complex signal is needed. This more complex signal does not have the ability to detect targets as deeply as the reference signal.

How does moisture in the soil affect the performance of my metal detector?

Most metal detectors can be fooled by large rusty items. When the soil is moist, the corrosion is worse and makes the item look larger. This is especially true of circular items like bottle caps and washers. Metals like iron and steel easily corrode in damp soil, but gold does not. Silver corrodes much less than copper, brass or bronze. Large pieces of iron sound different and experienced users don’t dig up large pieces of iron very often.