Using a metal detector changes your perspective on just how many junk metal objects there are in the ground. The excitement of finding money or jewelry can lose its thrill after digging 12 hairpins, 6 nails, 8 ketchup packets, and 50 pull-tabs. Some people will, at this point, proudly proclaim that they just crank up their discrimination control and avoid the junk metal.
Should you use your detector’s ability to discriminate or not? The answer to that question lies in learning more about the discrimination process. If you decide to eliminate certain types of metal from your searches, there may be consequences.
The discrimination control on most detectors is a progressive control. This means that as you turn it up, all metals below the current setting will be eliminated. In other words, when you turn it up past iron, foil, and pull-tabs, you eliminate all of them. Some metal detectors use a “notch” type of discrimination, which allows you to select only the specific metals you wish to discriminate.
Metal objects are made from mixtures of metals. This includes gold jewelry and coins, as well as aluminum pull-tabs. As a result, discrimination is not perfect because it depends on what other metals were used in the mixture.
Add to that, a common scenario where two or more different metal objects are physically close to each other in the ground. One example would be a penny within a few inches of a gold ring. Now the discrimination process gets even more complicated.
A metal detector measures the electromagnetic conductivity of an object. Different metals, and mixtures of metals, have different conductivity. Iron is the least conductive, and silver is the most. Copper is a little less than silver, followed by bronze and brass, both of which have copper in their mixture.
Gold, platinum, nickel, and aluminum are all very close to each other in electromagnetic conductivity. When you set your discrimination to eliminate pull-tabs, you also eliminate gold and platinum.
So what are you supposed to do? Here are a few things that will help you get the most from your metal detecting experience.
First, set your discrimination to zero, and start using the metal detector to see what kind of targets you find. Do this for at least 30 minutes and dig everything you find.
Second, separate the junk finds from the acceptable finds. If the junk greatly outnumbers the acceptable, then some discrimination may be in order.
Third, if you apply discrimination, always start at the lowest setting and search for a while at that setting. Increase it only if you continue to find large quantities of the same type of metal.
Professionals use little or no discrimination. Instead they use the sound of the detector, it’s indications, and their own common sense about the search area to determine whether the target is worth digging. As others have said before, “The best discrimination is right between your ears.”