In order to understand if metal detectors work for iron, one would need to understand how they work (learn more here). These machines are designed for a variety of purposes. Some are used to ensure security at airports or for treasure hunting. Depending on the purpose of the metal detector, one will get a different result. Technically, a metal detector should be able to work for all types of metals.
In order to use a metal detector, one needs to understand a concept first developed over two centuries ago. Electrical powers from power plants come from the activity of magnetism. However, electricity also generates magnetism. This is the concept that is used when one rolls a copper wire around an iron nail. In summary electricity and magnetism are two halves of the same things. A metal detector utilizes this unique relationship to detect various ferrous and non-ferrous objects in the earth.
A simple Metal Detector
While there are various complex designs used in metal detectors, basic ones utilize the following concept. A metal detector has a coil of wire attached to an iron core at the head of the detector. Electricity runs through this coil as an electric current. This current causes the head of the detector to generate a magnetic field. This magnetic field is usually about two feet long.
The field generated interacts with any metallic object in the ground. When it does, the action causes a weak electric current to develop in the metallic object. However, this weak current also develops magnetism. At the head of the detector, a second coil detects this magnetism generated from the ground. The magnetic field is then transmitted to a speaker located on the upper part of the detector. As a result, the person carrying the detector can realize if there is an object in the ground.
Ignoring Iron Using a metal Object
Most of the metal pieces one will find in the ground will most likely be made of iron. However, most people who purchase a metal detector want to find valuable objects such as gold. The problem is that gold is non-ferrous and produces a very weak signal. As a result, in order to detect gold, one needs a metal detector that is fine-tuned to avoid most ferrous objects. This is achieved by filtering out the high tone generated by ferrous materials.
However, this also means one is more likely to detect things such as pull-tabs. Still, there is unlikely to be much gold just lying around in the earth. As a result, when one detects this weak signal, make sure to pass the detector over the area a few more times. This will ensure the one can more accurately pinpoint where the object is located. It will also save one the amount of digging time required.
Metal detectors have come a long way since they were first invented. Now they even have features such as digital displays. This makes it much easier to interpret data and avoid wasting time digging up valueless objects.