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Four-point measurement of resistance between voltage sense connections 2 and 3. Current is supplied via force connections 1 and 4. In electrical engineering, four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements ...
Contact resistance values are typically small (in the microohm to milliohm range). Contact resistance can cause significant voltage drops and heating in circuits with high current. Because contact resistance adds to the intrinsic resistance of the conductors, it can cause significant measurement errors when exact resistance values are needed.
In the 4-point bending test, the specimen is placed on two supports and loaded in the middle by a test punch with two loading points. This results in a constant bending moment between the two supports. Consequently, a shear-free zone is created, where the specimen is subjected only to bending.
The simplest example given by Thimbleby of a possible problem when using an immediate-execution calculator is 4 × (−5). As a written formula the value of this is −20 because the minus sign is intended to indicate a negative number, rather than a subtraction, and this is the way that it would be interpreted by a formula calculator.
Text and/or other creative content from this version of was copied or moved into Bearing (mechanical) with this edit on 26 July 2010. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists.