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Wire gauge is a measurement of wire diameter. This determines the amount of electric current the wire can safely carry, as well as its electrical resistance and weight.
Wire gauges may be broadly divided into two groups, the empirical and the geometric. The first includes all the older gauge measurements, notably the Birmingham gauge (B.W.G. or Stubs) and the Lancashire. The origin of the B.W.G. is obscure. The numbers of wire were in common use earlier than 1735. It is believed that they originally were based on the series of drawn wires, No. 1 being the original rod, and succeeding numbers corresponding with each draw, so that No. 10, for example, would have passed ten times through the draw plate. But the Birmingham and the Lancashire gauge, the latter being based on an averaging of the dimensions collated from a large number of the former in the possession of Peter Stubs of Warrington, have long held the leading position, and are still retained and used probably to a greater extent than the more recent geometrical gauges.
The first attempt to adopt a geometrical system was made by Messrs Brown & Sharpe in 1855. They established a regular progression of thirty-nine steps between the English sizes, No. 0000 (460 mils or about 12 mm) and No. 36 (5 mils or about 0.13 mm). Each diameter was multiplied by 0.890526 to give the next lower size. This is now the American wire gauge (AWG), and is prevalent in North America and used to some extent in over 65 countries, with a market share of about 30% of all power and control wires and cables.
The Imperial Standard Wire Gauge, which has been sanctioned by the British Board of Trade, was formulated by J. Latimer Clark. Following one of its recommendations, it differs from pre-existing gauges scarcely more than they differ among themselves, and is based on a rational system, the basis being the circular mil. No. 7/0, the largest size, is 0.50 inches (500 mils or 12.7 mm) in diameter (1570 circular mils circumference), and the smallest, No. 50, is 0.001 inches (1 mil or 25.4 μm) in diameter (80 circular mils area). Between each step the diameter, or thickness, diminishes by 10.557%, and the area and weight diminish by ~ 20%.
None of the above systems of measurement is part of the metric system.
The current British Standard for metallic materials including wire is BS 6722:1986, which is a solely metric standard, superseding 3737:1964, which used the SWG system.
The IEC 60228, used in most parts of the world, defines standard wire sizes based on their cross-sectional areas as expressed in mm2.Each wire size has to respect a maximum resistivity value.
In commerce, the sizes of wire are estimated by devices, also called gauges, which consist of plates of circular or oblong form having notches of different widths around their edges to receive wire and sheet metals of different thicknesses. Each notch is stamped with a number, and the wire or sheet, which just fits a given notch, is stated to be of, say, No. 10, 11, 12, etc., of the wire gauge.
The circular forms of wire gauge measurement devices are the most popular, and are generally 3 3⁄4 inches (95 mm) in diameter, with thirty-six notches; many have the decimal equivalents of the sizes stamped on the back. Oblong plates are similarly notched. Rolling mill gauges are also oblong in form. Many gauges are made with a wedge-like slot into which the wire is thrust; one edge being graduated, the point at which the movement of the wire is arrested gives its size. The graduations are those of standard wire, or in thousandths of an inch. In some cases both edges are graduated differently in order to allow comparison between two systems of measurement. A few gauges are made with holes into which the wire has to be thrust. All gauges are hardened and ground to dimensions.
In some applications wire sizes are specified as the cross sectional area of the wire, usually in mm². Advantages of this system include the ability to readily calculate the physical dimensions or weight of wire, ability to take account of non-circular wire, and ease of calculation of electrical properties.
United States customary units are a system of measurements commonly used in the United States since it was formalized in 1832. The United States customary system developed from English units which were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures was overhauled in 1824 to create the imperial system, which was officially adopted in 1826, changing the definitions of some of its units. Subsequently, while many U.S. units are essentially similar to their imperial counterparts, there are significant differences between the systems.
American Wire Gauge (AWG), also known as the Brown & Sharpe wire gauge, is a logarithmic stepped standardized wire gauge system used since 1857, predominantly in North America, for the diameters of round, solid, nonferrous, electrically conducting wire. Dimensions of the wires are given in ASTM standard B 258. The cross-sectional area of each gauge is an important factor for determining its current-carrying ampacity.
A DC connector is an electrical connector for supplying direct current (DC) power.
IEC 60309 is a series of international standards from the International Electrotechnical Commission (IEC) for "plugs, socket-outlets and couplers for industrial purposes". The maximum voltage allowed by the standard is 1000 V DC or AC; the maximum current, 800 A; and the maximum frequency, 500 Hz. The ambient temperature range is −25 °C to 40 °C.
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. A screw thread is the essential feature of the screw as a simple machine and also as a threaded fastener.
IEC 60228 is the International Electrotechnical Commission's international standard on conductors of insulated cables. As of 2020 the current version is Third Edition 2004-11 Among other things, it defines a set of standard wire cross-sectional areas:
Metrication in Canada began in 1970 and ceased in 1985. While Canada has converted to the metric system for many purposes, there is still significant use of non-metric units and standards in many sectors of the Canadian economy and everyday life today. This is mainly due to historical ties with the United Kingdom, the traditional use of the imperial system of measurement in Canada, proximity to the United States, and strong public opposition to metrication during the transition period.
A rack unit is a unit of measure defined as 1 3⁄4 inches (44.45 mm). It is most frequently used as a measurement of the overall height of 19-inch and 23-inch rack frames, as well as the height of equipment that mounts in these frames, whereby the height of the frame or equipment is expressed as multiples of rack units. For example, a typical full-size rack cage is 42U high, while equipment is typically 1U, 2U, 3U, or 4U high.
A circular mil is a unit of area, equal to the area of a circle with a diameter of one mil. It corresponds to approximately 5.067×10−4 mm2. It is a unit intended for referring to the area of a wire with a circular cross section. As the definition of the unit contains π, it is easy to calculate area values in circular mils knowing the diameter in mils.
A thermoplastic-sheathed cable (TPS) consists of a toughened outer sheath of polyvinyl chloride (PVC) thermoplastic, covering one or more individual annealed copper conductors, themselves insulated with PVC. This type of wiring is commonly used for residential and light commercial construction in many countries. The flat version of the cable, with two insulated conductors and an uninsulated earth conductor, is referred to as twin and earth. In mainland Europe, a round equivalent is more common.
A thousandth of an inch is a derived unit of length in a system of units using inches. Equal to 1⁄1000 of an inch, a thousandth is commonly called a thou or particularly in North America a mil.
Jewelry wire is wire, usually copper, brass, nickel, aluminium, silver, or gold, used in jewelry making.
Wollaston wire is a very fine platinum wire clad in silver and used in electrical instruments. For most uses, the silver cladding is etched away by acid to expose the platinum core.
British Standard Wire Gauge is a unit for denoting wire size given by BS 3737:1964. It is also known as the Imperial Wire Gauge or British Standard Gauge. Use of SWG sizes has fallen greatly in popularity, but is still used as a measure of thickness in guitar strings and some electrical wire. Cross sectional area in square millimetres is now the more usual size measurement for wires used in electrical installation cables. The current British Standard for metallic materials such as wire and sheet is BS 6722:1986, which is a solely metric standard.
The distinction between real value and nominal value occurs in many fields. From a philosophical viewpoint, nominal value represents an accepted condition, which is a goal or an approximation, as opposed to the real value, which is always present.
In electrical engineering, IEC 60269 is a set of technical standards for low-voltage power fuses. The standard is in four volumes, which describe general requirements, fuses for industrial and commercial applications, fuses for residential applications, and fuses to protect semiconductor devices. The IEC standard unifies several national standards, thereby improving the interchangeability of fuses in international trade. All fuses of different technologies tested to meet IEC standards will have similar time-current characteristics, which simplifies design and maintenance.
Standard battery nomenclature describes portable dry cell batteries that have physical dimensions and electrical characteristics interchangeable between manufacturers. The long history of disposable dry cells means that many different manufacturer-specific and national standards were used to designate sizes, long before international standards were reached. Technical standards for battery sizes and types are set by standards organizations such as International Electrotechnical Commission (IEC) and American National Standards Institute (ANSI). Popular sizes are still referred to by old standard or manufacturer designations, and some non-systematic designations have been included in current international standards due to wide use.
A lightbulb socket, light socket, lamp socket or lampholder is a device which mechanically supports and provides electrical connections for a compatible electric lamp. Sockets allow lamps to be safely and conveniently replaced (re-lamping). There are many different standards for lampholders, including early de facto standards and later standards created by various standards bodies. Many of the later standards conform to a general coding system in which a socket type is designated by a letter or abbreviation followed by a number.
Body jewelry sizes express the thickness of an item of body jewelry, using one of several possible systems.
FASTON terminals are connectors that are widely used in electronic and electrical equipment. These terminals are manufactured by many companies, commonly using the term "quick disconnect", "tab" terminals, or blade connectors. They are similar in size to some of the Packard terminals, such as Packard 56, and may have been derived from them.