Analysis Of The Wheatstone Bridge

Analysis Of The Wheatst atomic public figure 53 distichThis Term Paper is almost topic Wheatst unity link up. A Wheatstone distich is a device which is employ to get under ones skin the unnamed resisitance. It is an promoter or a circumference consisting of four-spot-spot electrical ohmic oppositions or their equivalent in series which is apply to determine the value of an unacknowledged fortress when the other three resistances atomic number 18 cognise. If talk in mevery little detail past wheatstone pair contains the four resistance in which one is unkown resistance which we have to find ,one is vari fit resistance which is withal c all(prenominal)ed the rheostat of the circuit and two cognize resistance. It also contains the galvanometer for the detection of the received and it is also use to find the direction of ongoing.The various use of wheatstone linkwork is as under-It is is used by galvanic force play distributors to accurately locate breaks i n a power line.It is also used to admonisher sensor devices such as strain gauges. Such devices change their inwrought resistance according to the unique(predicate) level of strain (or pressure, temperature, etc.), and serve as the enigmatical resistor RX.Meter bridge deck, post office box and Carey cherish bridge are instrumentates based on the principle of Wheatstone bridgeThe sanctioned use is to measure the isolated resistance.What is a wheatstone bridge?The wheatstone bridge is an instrument which is generally used to measure electrical resistance by fit a bridge circuit. The bridge circuit contains four resistance, one of which contains the un cognize resistance ,one variable resistance and two known resistance.Introductions to Wheatstone distich-Wheatstone Bridge, a device for measurement electrical resistance. In wheat-stone bridge four resistance R1, R2, R3and R4are affiliated end to end with each other to skeleton a closed loop. A sensitive galvanometer Gis c onnected in the midst of their junctions.One form of Wheatstone bridge is shown in the following example-For example- When the Wheatstone bridge is connected in an electrical circuit, part of the stream flows to the object whose resistance is unknown and part of catamenia flows to the resistor of known resistance. If more real flows finished one side of the circuit than the other, the galvanometer shows the deflection. Due to potential drop difference ca-ca in between them when the current flows equally along both sides of the bridge then the galvanometer shows zero deflection.Thus the bridge is balanced, the unknown resistance is metrical by using formula. The formula is-R1/R2=R3/R4Where R1 is the unknown resistance.R2 is the variable resistanceR3 and R4 are the known resistancesGenerally wheat-stone bridge is used to determine unknown resistances.Conditions for wheatstone bridge-There are two contexts for wheatstone bridge which is as under-Condition-1Galvanometer is ince ssantly in zero potential in the circuit.Condition-2We should have to take one variable resistance.History of Wheatstone bridge- link 1Wheatstones bridge circuit diagram.A Wheatstone bridgeis an electrical circuit invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. It is used to measure an unknown electrical resistance by equilibrate two pegs of a bridge circuit, one leg of bridge contains the unknown component and variable component. Its operation is similar to the originalpotentiometer.Potentiometer - link 2A potentiometeris an instrument for touchstone the potential ( potential drop) in a circuit,they were used in measuring emf.Creation of Wheatstone bridge by different scientists- link 51) A scientist and mathematicsematician, Samuel Hunter Christie, unquestionable the circuit to measure unknown electrical resistances and first described it in 1833. The bridge worked because of the special diamond-shaped ar windment of the four resistors. Electrical current from a battery split into two parallel branches of the circuit. One consisted of a resistor with a fixed, known resistance and an adjustable resistor, also with a known resistance. The other leg contained a resistor of fixed and known resistance and some other whose resistance needed to be determined. By using a galvanometer to balance the current flowing through the two branches, Christie could, with the help of a little math, determine the value of the unknown resistor.2) Then another British scientist, Wheatstone, came across Christies description of the instrument, which Wheatstone referred to as a differential resistance measurer. A prominent member of the Royal Society of London, Wheatstone was wellhead-positioned to give the tool a popularity boost. He gave an account of Christies invention at an 1843 lecture, and soon after it came to be called the Wheatstone bridge was used in telegraphy and other coats. Wheatstone himself, however, gave full faith for its invention to Christie. But in translations of his lecture that appeared in Germany and France the following year, Wheatstones ascription was nowhere to be found.In addition to bringing the device to semipublic attention, Wheatstone improved the design (Wheatstone developed the rheostat, a variable resistor) and found some(prenominal) new uses for it. By changing the type of elements contained in its legs, the Wheatstone bridge deal determine unknown capacitances, inductances, frequencies and other properties.Besides Wheatstone, several other scientists helped gestate the range of the device, including William Thomson, Lord Kelvin and James Clerk Maxwell. This sensitive, accurate rule for measuring resistance is still widely used today.Theory of Wheatstone Bridge-To understand this circuit, consider the following Figure to be two potential dividers shown belowWhen the bridge is balanced, the electromotive forces measured by V1and V2are equal, hence no current flows through the Galvanometer G in above figure. Since V1and V2are at the same voltage, the resistance ratios Rx/RSand l1/l2are equal. Because the slide wire has a uniform resistance per unit length, the length ratios l1/l2is equivalent to resistance ratio R1/R2.How Equipment of wheatstone bridge works- Link 8The current flows from validatory to negative through the circuit.When it reaches Point Ain the diagram, it splits and travels through either one of two Known Resistors, R1 or R2. Resistance is measured in a unit called an ohm. Here we notice that when this applet initializes, the resistance at R1 is 1 K ohm, while at R2 it is also at 1 K ohm. after(prenominal) the diverging currents pass through their respective resistors (R1 or R2), each reaches another fork in the road. At this point, if the bridge is not balanced, some or all of the current from either the R1 or R2 path will diverge down this nitty-gritty path that bisects the square created by the circuit. The Galvanometer ispositioned on this middle path which generally tells the presence or absence of current.The direction of this current is determined by the value of the Variable Resistor(R3).Here at this eon the bridge is not balanced because the ratio of resistance on the known leg (R1/R2) is not equal to the ratio on the unknown leg (R3/R4). This is where the variable resistor which is also called rheostat of the bridge comes into play. It rotter be alter until no current flows down the middle path. When that is achieved, the Galvanometer reads zero and the bridge is balanced. Achieve this balanced state by adjusting the Variable Resistorslider until the Galvanometer reads zero and no more current flows through the middle path. Notice how the arrows depicting current direction change as you manipulate the slider. The ohm value is displayed above the slider.By discovering the value of the variable resistor in the balanced bridge, you are able to determine what the unknown resista nce at R4 is, with a little mathR1/R2 = R3/R4orR4 = (R2 * R3) /R1So by using the above formula we toilet easily find out the unknown electrical resistance.Derivations-Derivation of Wheatstone Bridge-link 1First, Kirchhoffs first rule is used to find the currents in junctions Band DWhen thenI3= Ixand I1= I2(3)Then, Kirchhoffs second rule is used for finding the voltage in the loops ABDand BCDThe bridge is balanced when Ig= 0, so the second set of equatings force out be rewritten as.(1).(2)By dividing equation 1 by 2 we get-From the equation (3), I3= Ixand I1= I2. The desired value of Rxis now known to be given asIf all four resistor values and the translate voltage (VS) are known, the voltage across the bridge (VG) buttocks be found by working out the voltage from each potential divider and subtracting one from the other. The equation for this isThis can be simplified toWith boss B being (VG) positive, and node D being (VG) negative.Bridgeconatianing constant voltage and voltage gage -A basic Wheatstone bridge circuit contains four resistances, a constant voltage input, and a voltage gage, as illustrated below.For a given voltage input Vin, the currents flowing through ABCand ADCdepend on the resistances, i.e.,The voltage drops from Ato Band from Ato Dare given by,The voltage gage reading Vgcan then be obtained from,Now suppose that all resistances can change during the measurement. The alike(p) change in voltage reading will be,If the bridge is ab initio balanced, the initial voltage reading Vgshould be zero. This yields the following relationship between the four resistances,We can use this result to simplify the previous equation that includes the changes in the resistances. Doing so results in the solution for the change in Vg,where h is defined by,Moreover, when the resistance changes are small (which is the basic equation administration the Wheatstone bridge voltage in strain measurement. The coefficient is called the circuit efficiency.Equal-Resi stance Wheatstone Bridge forget me drug-In practice, one often uses the same resistance value for all four resistors, R1= R2= R3= R4= R. Noting that r = 1 in this case, the change in voltage can be further simplified to,By thoughtfully selecting the sucker and reference resistances, the Wheatstone bridge circuit can amplify small changes in resistance and/or compensate for changes in temperature.How to use the Wheatstone Bridge -In its basic application, a dc voltage (E) is applied to the Wheatstone Bridge, and a galvanometer (G) is used to monitor the balance condition. The values of R1 and R3 are precisely known, but do not have to be identical. R2 is a calibrated variable resistance, whose current value may be read from a dial or scale.An unknown resistor, RX, is connected as the fourth side of the circuit, and power is applied. R2 is adjusted until the galvanometer, G, reads zero current. At this point, RX = R2-R3/R1.This circuit is most sensitive when all four resistors have similar resistance values. However, the circuit works quite well in any event. If R2 can be varied over a 101 resistance range and R1 is of a similar value, we can switch decade values of R3 into and out of the circuit according to the range of value we expect from RX. Using this method, we can accurately measure any value of RX by moving one multiple-position switch and adjusting one precision potentiometer.Significance of wheatstone bridge - link 1The Wheatstone bridge illustrates the concept of a difference measurement, which can be extremely accurate. Variations on the Wheatstone bridge can be used to measure capacitance, inductance, impedance and other quantities, such as the amount of flammable gases in a sample, with an explosimeter. The Kelvin bridge was specially adapted from the Wheatstone bridge for measuring very low resistances. In many cases, the significance of measuring the unknown resistance is related to measuring the impact of some material phenomenon such as force, temperature, pressure, etc which thereby allows the use of Wheatstone bridge in measuring those elements indirectly.Applications of Wheatstone Bridge- Link 6,Link 7 A number of resistance measuring devices have been devised on the principle of wheatstone bridge.For example 1) Meter bridge, post office box and Carey nurse bridge are instruments based on the principle of Wheatstone bridge and are used to measure unknown resistance.2) A very common application in industry today is to monitor sensor devices such as strain gauges. Such devices change their internal resistance according to the specific level of strain (or pressure, temperature, etc.), and serve as the unknown resistor RX. However, quite of trying to constantly adjust R2 to balance the circuit, the galvanometer is replaced by a circuit that can be calibrated to record the degree of imbalance in the bridge as the value of strain or other condition being applied to the sensor.3) A third application is used by elect rical power distributors to accurately locate breaks in a power line. The method is fast and accurate, and does not require a large number of field technicians.Other applications abound in electronic circuits. Well fill a number of them in action as these pages continue to expand.Bridge circuits are widely used for the measurement of resistance, capacitance, and inductance. The resistive bridge, also known as Wheatstone bridge.Links used in the Term Paper-1)http//en.wikipedia.org/wiki/Wheatstone_bridge2) http//en.wikipedia.org/wiki/Potentiometer_%28measuring_instrument%293)http//www.efunda.com/designstandards/sensors/methods/wheatstone_bridge.cfm4) http//www.magnet.fsu.edu/education/tutorials/java/wheatstonebridge/index.html5) http//www.magnet.fsu.edu/education/tutorials/museum/wheatstonebridge.html6) http//www.citycollegiate.com/wheatstone_bridge.htm7) http//www.transtutors.com/physics-homework-help/current-electricity/wheatstone-bridge-and-potentiometer.aspx8) http//reocities.com /CapeCanaveral/8341/bridge.htm