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A Wheatstone bridge is a measuring instrument 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 balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer except that in potentiometer circuits the meter used is a sensitive galvanometer. Captain Nemo and Professor Aronnax contemplating measuring instruments in Twenty Thousand Leagues Under the Sea In physics and engineering, measurement is the activity of comparing physical quantities of real-world objects and events. ...
Samuel Hunter Christie (1784-1865) was a British scientist and mathematician. ...
Year 1833 (MDCCCXXXIII) was a common year starting on Tuesday (link will display the full calendar) of the Gregorian Calendar (or a common year starting on Sunday of the 12-day slower Julian calendar). ...
Charles Wheatstone Sir Charles Wheatstone (February 6, 1802 - October 19, 1875) was the British inventor of many innovations including the English concertina the Stereoscope an early form of microphone the Playfair cipher (named for Lord Playfair, the person who publicized it) He was a major figure in the development of...
Year 1843 (MDCCCXLIII) was a common year starting on Sunday (link will display the full calendar) of the Gregorian Calendar (or a common year starting on Friday of the 12-day slower Julian calendar). ...
Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ...
A bridge circuit is a type of electrical circuit in which the current in a conductor splits into two parallel paths and then recombines into a single conductor, thereby enclosing a loop. ...
It has been suggested that Determining emf of primary cells using potentiometer be merged into this article or section. ...
In the circuit at right, Rx is the unknown resistance to be measured; R1, R2 and R3 are resistors of known resistance and the resistance of R2 is adjustable. If the ratio of the two resistances in the known leg (R2 / R1) is equal to the ratio of the two in the unknown leg (Rx / R3), then the voltage between the two midpoints will be zero and no current will flow between the midpoints. R2 is varied until this condition is reached. The current direction indicates if R2 is too high or too low. Image File history File links Wheatstonebridge. ...
Image File history File links Wheatstonebridge. ...
The circuit diagram for a 4 bit TTL counter, a type of state machine A circuit diagram (also known as an electrical diagram, elementary diagram, or electronic schematic) is a simplified conventional pictorial representation of an electrical circuit. ...
International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ...
In electricity, current refers to electric current, which is the flow of electric charge. ...
Detecting zero current can be done to extremely high accuracy (see Galvanometer). Therefore, if R1, R2 and R3 are known to high precision, then Rx can be measured to high precision. Very small changes in Rx disrupt the balance and are readily detected. Wire carrying current to be measured Restoring spring N and S are poles of magnet A galvanometer is a type of ammeter — an instrument for detecting and measuring electric current. ...
If the bridge is balanced, which means that the current through the galvanometer Rg is equal to zero, the equivalent resistance of the circuit between the source voltage terminals is:
R1 + R2 in parallel with R3 + Rx
 Alternately, at this point of balance, the ratio of R2 / R1 = Rx / R3
Therefore, Rx = (R2 / R1) * R3
Alternatively, if R1, R2, and R3 are known, but R2 is not adjustable, the voltage or current flow through the meter can be used to calculate the value of Rx, using Kirchhoff's circuit laws (also known as Kirchhoff's rules). This setup is frequently used in strain gauge and Resistance Temperature Detector measurements, as it is usually faster to read a voltage level off a meter than to adjust a resistance to zero the voltage. Not to be confused with Kerckhoffs principle. ...
Typical foil strain gauge. ...
A resistance temperature detector measures the relationship between electrical resistance and temperature. ...
Derivation
First, we can use Kirchhoff's first rule to find the currents in junctions B and D:  Then, we use Kirchhoff's second rule for finding the voltage in the loops ABD and get them, giving:  From the first rule, we know that I3 = Ix and I1 = I2. The desired value of Rx is now known to be given as:  If all four resistor values and the supply voltage (Vs) are known, the voltage across the bridge (V) can be found by working out the voltage from each potential divider and subtracting one from the other. The equation for this is: In electronics, a voltage divider or resistor divider is a design technique used to create a voltage (Vout) which is proportional to another voltage (Vin). ...
 This can be simplified to:  The 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 combustible gases in a sample, with an explosimeter. The Kelvin Double bridge was one specially adapted for measuring very low resistances. This was invented in 1861 by William Thomson, Lord Kelvin. Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ...
An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Φ through the circuit. ...
Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ...
An explosimeter is a device which is used to measure the amount of combustible gases present in a sample. ...
For other persons named William Thomson, see William Thomson (disambiguation). ...
The concept was extended to alternating current measurements by James Clerk Maxwell in 1865 and further improved by Alan Blumlein in about 1926. City lights viewed in a motion blurred exposure. ...
James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères...
Alan Dower Blumlein was an electronics engineer who made a great many inventions in telecommunications, sound recording, stereo, television and radar. ...
Modification of the fundamental bridge The Wheatstone bridge is the fundamental bridge, but there are other modifications that can be made to measure various kinds of resistances when the fundamental Wheatstone bridge is not suitable. Some of the modifications are: - Karey-Foster Slide-wire bridge
- Kelvin Varley Slide
- Kelvin Double bridge
See also Image File history File links Nuvola_apps_ksim. ...
Typical foil strain gauge. ...
It has been suggested that Determining emf of primary cells using potentiometer be merged into this article or section. ...
In electronics, a voltage divider or resistor divider is a design technique used to create a voltage (Vout) which is proportional to another voltage (Vin). ...
An Ohmmeter is an electrical measuring instrument that measures electrical resistance, the opposition to the flow of an electric current. ...
A resistance temperature detector measures the relationship between electrical resistance and temperature. ...
A Maxwell bridge is a type of Wheatstone bridge used to measure an unknown inductance in terms of calibrated resistance and capacitance. ...
Mark Super VII Quantum E-meter An E-meter is an electronic device manufactured by the Church of Scientology at their Gold Base production facility. ...
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