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Although the actual inventor of the hand-held metal detector is disputed, the hand-held metal detector was made in 1925 and was first patented by Dr. Gerhard Fisher in 1931. A metal detector had been invented some forty years earlier (1881) by Alexander Graham Bell for the sole purpose of locating a lead bullet in President James A. Garfield.
After Lee de Forest invented the triode in 1907 metal detectors used vacuum tubes to operate and became more sensitive but still quite cumbersome. One of the early common uses of the first metal detectors, for example, was the detection of landmines and unexploded bombs in a number of European countries following the First and Second World Wars.
An inclinometer or clinometer is an instrument used for measuring angles of slope, elevation, or depression of an object with respect to gravity's direction. It is also known as a tilt indicator , tilt sensor , tilt meter , slope alert , slope gauge , gradient meter , gradiometer , level gauge , level meter , declinometer , and pitch & roll ...
Date Place of discovery Year of discovery Current location Ashdon Hoard: Viking Age United Kingdom: 1984 Fitzwilliam Museum: Bedale Hoard: 9th to 10th century United Kingdom: 2012 Yorkshire Museum: Bredon Hill Hoard: 3rd century United Kingdom: 2011 Worcester City Art Gallery & Museum: Chew Valley Hoard: 11th century United Kingdom: 2019 ...
1881 Metal detector. Metal detectors use electromagnetic induction to detect metal. In 1881, the Scots-American named Alexander Graham Bell invented the first metal detector as President James Garfield lay dying from a fatal gunshot wound. Despite an effort to locate the lodged bullet, Bell's invention proved to be unsuccessful as the metal ...
1959: The MOSFET (MOS transistor) is invented by the Egyptian Mohamed Atalla and the Korean Dawon Kahng at Bell Labs. It is used in almost all modern electronic products. It was smaller, faster, more reliable and cheaper to manufacture than earlier bipolar transistors, leading to a revolution in computers, controls and communication. [492] [493 ...
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The first widely used detector was the coherer, invented in 1890. The coherer was a very poor detector, insensitive and prone to false triggering due to impulsive noise, which motivated much research to find better radio wave detectors.