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A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of the circuit is its ability to provide extremely accurate measurements (in contrast with something like a simple voltage divider ). [ 1 ]
Under normal conditions there is a stable heat flow from the filament to the detector body. When an analyte elutes and the thermal conductivity of the column effluent is reduced, the filament heats up and changes resistance. This resistance change is often sensed by a Wheatstone bridge circuit which produces a measurable voltage change. The ...
Haarman who introduced the electronic Wheatstone bridge that is a common feature of other modern transient methods. [ 9 ] [ 10 ] 1976 - Healy et al. published a journal article detailing the theory of the transient hot wire, described by an ideal solution with appropriate corrections to address effects like convection, among others.
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 R 1 and R 3 (see diagram), one whose resistance is to be determined R x , and one which is variable and calibrated R 2 .
Thermal conductivity, frequently represented by k, is a property that relates the rate of heat loss per unit area of a material to its rate of change of temperature. Essentially, it is a value that accounts for any property of the material that could change the way it conducts heat. [ 1 ]
This applies equally to balanced bridge and fixed bridge system. For a balanced bridge usual setting is with R2 = R1, and R3 around the middle of the range of the RTD. So for example, if we are going to measure between 0 and 100 °C (32 and 212 °F), RTD resistance will range from 100 Ω to 138.5 Ω. We would choose R3 = 120 Ω.
Calibration is conducted incrementally starting working in ascending or descending order. For example, in the case of a 60 tonne load cell, then specific test weights that measure in 5, 10, 20, 40 and 60 tonne increments may be used; a five step calibration process is usually sufficient for ensuring a device is accurately calibrated.
The two remaining arms are the nearly equal resistances P and Q, connected in the inner gaps of the bridge. A standard Wheatstone bridge for comparison. Points A, B, C and D in both circuit diagrams correspond. X and Y correspond to R 1 and R 2, P and Q correspond to R 3 and R X. Note that with the Carey Foster bridge, we are measuring R 1 ...