The Invention of a Gold Detector
Metal detectors are electronic devices that emit a signal when a piece of gold is near them. These devices are used by treasure hunters and archaeologists to locate objects of interest. They can also be used to find lost items. They work by sending out radio waves and detecting the reflected signals from the objects. The signals are then processed to determine what the object is made of. Some of the more expensive models use X-ray fluorescence to figure out what an item is made of. This allows them to read a piece of gold and tell what it is exactly made out of.
The invention of a gold detector started in 1830 when geologist and mining engineer R. W. Fox discovered that electricity will flow through metallic ores and solid metal objects. This led to the invention of the first metal locator which consisted of a battery, a metal rod and a length of wire. This was a crude version of what we know today as a gold pan.
In the 1920's Gerhard Fisher developed and patented the first hand-held metal detector. This was based on the electromagnetic concept that Kosacki had developed earlier. It was a great success until he noticed that the signals it produced would go awry when large metal objects or other conductive materials were present nearby. This was due to the fact that these objects interfered with the electric field between the transmitter and receiver.
It was later realised that ground mineralisation interferes with high frequency and that it is possible to overcome this using selectivity or discrimination. This was achieved by tuning one or more coils so that they can detect certain groups of metals while ignoring others. The ability to selectively detect desirable metals has allowed a number of different detector types to be developed.
The most popular gold detectors operate at a frequency between 3 and 100 kHz and are electro-magnetically tuned so that when they are switched on, their electromagnetic field produces a signal whenever a piece of metal is in its vicinity. This is a result of eddy currents being induced in the metal by the alternating magnetic field. The ability to differentiate between different metals is the result of the fact that each metal has a different phase response to alternating current. Longer wavelengths (low frequency) penetrate the ground deeper and select for higher conductivity targets such as silver and copper, while shorter waves (higher frequency) are less ground penetrating and select for low conductivity metals such as iron.
Another method of testing gold is to use an acid test. This test can be done at home with a few simple items. To do this you need a piece of gold and some white vinegar. The acid will react with the gold and change its colour. If the colour changes then it is not pure gold. This test is also a good way to determine if an item of gold جهاز لكشف المعادن is plated.