Sunday 22 October 2017

3-wire load cells and wheatstone bridges from a bathroom scale


I am involved with a 4H project looking to take some weight measurements with bee hives and am trying to figure out some 3-wire load sensors to do just that.


I have four 3-wire sensors (load sensors/strain gauges) from one bathroom scale (each sensor was at a corner). Each sensor has a red, black and white wire. The resistance between the red wire and either the black or white wire is 1k ohms. The resistance between the white and black wires is 2k ohms (the resistance between the leads on my load cells and each came away with R->B=1K, R->W=1K, B->W=2k).


Because of this, I was told each 3-wire load sensor represents 1/2 of a Wheatstone bridge (each sensor containing two 1k resistance legs).


I can get my head around the single wheatstone application but I'm confused how a scale would work when made from two wheatstone bridges. My question is, if this is so, why would a scale require two Wheatstone bridges (remember, all four 3-wire sensors came from one bathroom scale)?




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