The MGS Precious Metals Blog

Manhattan Gold & Silver is an industry leader in precious metal pricing and refining with more than 30 years of experience. During our time in the business, we’ve found the topic of precious metals to be a vast and interesting one. Here on our precious metals blog, we write in-depth posts about the science of precious metal refining, historical and modern uses for precious metals, market news, and much more. Subscribe to our RSS feed to stay current, and discuss the latest posts on our Facebook page.

How Metal Detectors Find Gold

December 26, 2017 07:00
How Metal Detectors Find Gold

By far, gold detectors are the most popular tool among amateur prospectors and treasure hunters. For all intents and purposes, gold detectors are metal detectors – but specifically constructed and calibrated for gold hunting. To explain how these tools excel at finding gold, it helps to understand the science behind basic metal detectors.

Metal detectors work by transmitting an electromagnetic field into the ground, then analyzing the return signal. The electromagnetic field transmitted by the detector induces loops of electrical current, called eddy currents, within conductive materials (i.e. metals). Eddy currents generate their own electromagnetic field, which the detector receives and analyzes.
Gold detectors take this process a step further by measuring inductance and conductivity. Basically, inductance refers to the amount of eddy currents produced in the target. Conductivity refers to how easily those currents flow. By measuring the size of the eddy currents and how fast they are traveling, gold detectors can calculate the "time constant" of a target.

Time constants can vary considerably between targets. For example, bits of aluminum foil have very short time constants, gold coins and rings have longer time constants, and scraps of steel, iron, and other ferrous metals have even longer time constants. Gold detectors can be calibrated to specifically search for targets that fall within that “middle” range. Unfortunately, it’s not a foolproof method. The size, shape, and distance of a target (along with other environmental variables) affect the accuracy of the detector’s time constant calculation. To compensate, gold detectors can be re-calibrated on-the-fly to search for a broader or narrower range of time constants.

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