From what I read digital scales use load cells/strain gauges to detect force applied, but how does a load cell actually work under the circular metal plate that you see in digital scales? Is that metal plate/pan a special plate or is it just there to hold matter over the load cell?
For more precise microbalances I also know that magnetic sensors are used. Can someone explain how magnets are used to read off pressure/force? Do the metal pans in microbalances also affect the magnetic sensors?
In: Technology
Strain is the technical name for when things change shape due to mechanical forces. So, a strain gauge type of load cell is usually just a piece of something conductive that will change shape slightly (ie strain) when a force is applied.
The resistance of a conductive thing is related to the length and area of the thing. So when the conductive part of the load cell is subjected to a force, it changes shape slightly which changes the length and area, in turn changing resistance of the thing slightly.
Hook up a known voltage across the conductive thing and the changes in resistance will cause the current flowing across the thing to change slightly. Hook a current meter into the circuit and you now have a numeric read out that varies in proportion with the weight placed on the cell. Calibrate it with some known weights and you’re away.
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