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Murray Loop Bridge
The Murray loop bridge is a bridge circuit used for locating faults in underground or underwater Electrical cable, cables. It has been used for more than 100 yearsLatimer Clark, Robert Sabine ''Electrical tables and formulæ: for use of telegraph inspectors and operators'', E. & F.N. Spon, 1871 pp. 41-44 but is being replaced by the more precise Time-domain reflectometer. One end of the faulted cable is connected through a pair of resistors to the voltage source. Also a null detector is connected. The other end of the cable is shorted. The bridge is brought to balance by changing the values of ''RB1'' and ''RB2'', which is achieved when: \frac = \frac which is equivalent to: R_x = (R_g + R_y) \cdot \frac The value of resistance ''Rx'' is proportional the length ''Lx'', thus the location of the fault can be calculated: L_x = 2 \cdot L \cdot \frac where ''L'' is the total length of the cable under test - a value proportional to ''Rg''. The method assumes a single fault exis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Murray Loop Bridge
The Murray loop bridge is a bridge circuit used for locating faults in underground or underwater Electrical cable, cables. It has been used for more than 100 yearsLatimer Clark, Robert Sabine ''Electrical tables and formulæ: for use of telegraph inspectors and operators'', E. & F.N. Spon, 1871 pp. 41-44 but is being replaced by the more precise Time-domain reflectometer. One end of the faulted cable is connected through a pair of resistors to the voltage source. Also a null detector is connected. The other end of the cable is shorted. The bridge is brought to balance by changing the values of ''RB1'' and ''RB2'', which is achieved when: \frac = \frac which is equivalent to: R_x = (R_g + R_y) \cdot \frac The value of resistance ''Rx'' is proportional the length ''Lx'', thus the location of the fault can be calculated: L_x = 2 \cdot L \cdot \frac where ''L'' is the total length of the cable under test - a value proportional to ''Rg''. The method assumes a single fault exis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leeds & Northrup Type S Test Set No
Leeds () is a city and the administrative centre of the City of Leeds district in West Yorkshire, England. It is built around the River Aire and is in the eastern foothills of the Pennines. It is also the third-largest settlement (by population) in England, after London and Birmingham. The city was a small manorial borough in the 13th century and a market town in the 16th century. It expanded by becoming a major production centre, including of carbonated water where it was invented in the 1760s, and trading centre (mainly with wool) for the 17th and 18th centuries. It was a major mill town during the Industrial Revolution. It was also known for its flax industry, Foundry, iron foundries, engineering and printing, as well as shopping, with several surviving Victorian era arcades, such as Leeds Kirkgate Market, Kirkgate Market. City status was awarded in 1893, a populous urban centre formed in the following century which absorbed surrounding villages and overtook the nearby York ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bridge Circuit
A bridge circuit is a topology of electrical circuitry in which two circuit branches (usually in parallel with each other) are "bridged" by a third branch connected between the first two branches at some intermediate point along them. The bridge was originally developed for laboratory measurement purposes and one of the intermediate bridging points is often adjustable when so used. Bridge circuits now find many applications, both linear and non-linear, including in instrumentation, filtering and power conversion. The best-known bridge circuit, the Wheatstone bridge, was invented by Samuel Hunter Christie and popularized by Charles Wheatstone, and is used for measuring resistance. It is constructed from four resistors, two of known values R1 and R3 (see diagram), one whose resistance is to be determined Rx, and one which is variable and calibrated R2. Two opposite vertices are connected to a source of electric current, such as a battery, and a galvanometer is connected across t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Cable
An electrical cable is an assembly of one or more wires running side by side or bundled, which is used to carry electric current. One or more electrical cables and their corresponding connectors may be formed into a ''cable assembly'', which is not necessarily suitable for connecting two devices but can be a partial product (e.g. to be soldered onto a printed circuit board with a connector mounted to the housing). Cable assemblies can also take the form of a cable tree or cable harness, used to connect many terminals together. Etymology The original meaning of ''cable'' in the electrical wiring sense was for submarine telegraph cables that were armoured with iron or steel wires. Early attempts to lay submarine cables without armouring failed because they were too easily damaged. The armouring in these early days (mid-19th century) was implemented in separate factories to the factories making the cable cores. These companies were specialists in manufacturing wire rope of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-domain Reflectometer
A time-domain reflectometer (TDR) is an electronic instrument used to determine the characteristics of electrical lines by observing reflected waveforms. It can be used to characterize and locate faults in metallic cables (for example, twisted pair wire or coaxial cable). It can also be used to locate discontinuities in a connector, printed circuit board, or any other electrical path. Description A TDR measures reflections along a conductor. In order to measure those reflections, the TDR will transmit an incident signal onto the conductor and listen for its reflections. If the conductor is of a uniform impedance and is properly terminated, then there will be no reflections and the remaining incident signal will be absorbed at the far-end by the termination. Instead, if there are impedance variations, then some of the incident signal will be reflected back to the source. A TDR is similar in principle to radar. The impedance of the discontinuity can be determined from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resistor
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity. Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds and forms. Resisto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null Detector
A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. A galvanometer works by deflecting a pointer in response to an electric current flowing through a coil in a constant magnetic field. Galvanometers can be thought of as a kind of actuator. Galvanometers came from the observation, first noted by Hans Christian Ørsted in 1820, that a magnetic compass's needle deflects when near a wire having electric current. They were the first instruments used to detect and measure small amounts of current. André-Marie Ampère, who gave mathematical expression to Ørsted's discovery, named the instrument after the Italian electricity researcher Luigi Galvani, who in 1791 discovered the principle of the frog galvanoscope – that electric current would make the legs of a dead frog jerk. Galvanometers have been ess ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault (power Engineering)
In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire (phase or neutral) or a blown fuse or circuit breaker. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure. In a polyphase system, a fault may affect all phases equally, which is a "symmetric fault". If only some phases are affected, the resulting "asymmetric fault" becomes more complicated to analyse. The analysis of these types o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bridge Circuits
A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually something that is otherwise difficult or impossible to cross. There are many different designs of bridges, each serving a particular purpose and applicable to different situations. Designs of bridges vary depending on factors such as the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, and the material used to make it, and the funds available to build it. The earliest bridges were likely made with fallen trees and stepping stones. The Neolithic people built boardwalk bridges across marshland. The Arkadiko Bridge (dating from the 13th century BC, in the Peloponnese) is one of the oldest arch bridges still in existence and use. Etymology The ''Oxford English Dictionary'' traces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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