Uncoiling differences in metal detectors

There was a time when metal detecting was, well, sort of nerdy.

There was a time when metal detecting was, well, sort of nerdy.

Think middle-aged guys with knobby knees, baggy shorts and open-toed sandal shoes walking along the beach searching for dimes and quarters.

Things have changed – so have today’s metal detectors. While some are general purpose detectors, others are specifically designed to detect specific types of metals. I acquired my first metal detector with the idea of hunting for artifacts. I have since purchased a second detector to help look for gold.

Before I go any further, however, I do have to say that getting into metal detecting is not cheap. Good quality, general purpose detectors can cost anywhere from $500 to $1,000, while specific purpose detectors can run $5,000 and more. You don’t want to go out and buy a detector, as well as all the necessary gear, to find out after a couple of outings that it’s not for you. Do your homework first. Don’t just look at advertisements, go online and read actual user reviews.

Different metal detectors work in various ways. The type of metal detectors I own are referred to as Very Low Frequency (VLF) metal detectors. They work on the principle of a coil of wire (wrapped around a circular disk at the end of the handle) known as the transmitter coil. When electricity flows through the coil, a magnetic field is created around the disk. When a metal detector moves over a piece of metal, the magnetic field coming from the detector causes another magnetic field to appear around the metal. It is this second magnetic field that the detector picks up.

The metal detector has a second coil of wire in its head (known as the receiver coil) that is connected to a speaker. As the detector moves over the piece of metal, the magnetic field produced by the metal cuts through the coil. Electricity flows through the receiver coil and makes the loudspeaker beep.

The closer the transmitter coil is to the piece of metal, the stronger the magnetic field the transmitter coil creates and the stronger the magnetic field the metal creates in the receiver coil, the more current that flows to the speaker and the louder the beep.

I don’t claim to fully understand all that much about the electronics behind metal detectors, but I do know that the depth at which an object can be located depends on a number of factors such as the size of the metal object and the amount of iron and mineral content in the soil. I also know that objects such as pull tabs from beverage cans, coins, nails, metal relics and, yes, particles of gold all emit magnetic signatures. Learning to recognize the subtle difference between signals is challenge.

Most general purpose metal detectors can locate small objects such as coins to a depth of up to six inches, and larger objects to a depth of five feet and sometimes more. General purpose metal detectors are not typically designed to detect metal objects as small as a flake of gold, but they do offer far superior trash metal rejection compared to detectors designed specifically for gold prospecting. Having said that, better quality general purpose metal detectors usually have a setting which can effectively ‘discriminate’ gold from other metals.

Determine which detector is the best fit for you, and then, after you’ve bought it, make sure to read the instructions.

Practice in your backyard by putting some coins and/or a metal artifact on the ground. Listen to the sound your detector makes as you pass over the different items. Also, try passing the coil over bottle caps, drink can pull tabs nails and pieces of scrap metal. Listen to the different sounds each makes. Remember when you are out in the field, you will come across a lot of ‘trash’ before find any treasures.

While on the subject of trash and treasures, one thing I discovered is that when it comes to ‘treasure hunting’ and metal detectors, sometimes some of the best finds are to be found at garage sales. I found my first metal detector at a garage sale.


Salmon Arm Observer