How do scales that are capable of measuring incredibly tiny amounts of things actually work?
In: Technology
All the other answers are great; they describe practical scales that measure in the sub milligrams. But to give you something even deeper, some specialized scales can actually go to higher resolutions, measuring picograms, and more recently down to the yoctogram resolution (10^(-24) grams) which is basically the mass of a single proton.
They essentially work using a very basic law in physics. They have an oscillating beam (for the yg range, they use nanotubes for beams). Without getting too much into detail, if something is oscillating, it has a given natural frequency (a rate at which if you move it at, it will produce maximum deflection or amplitude). When you apply a force, no matter how tiny, to this oscillating structure, its natural frequency will change. This sounds insane to measure but it’s not, because measuring frequency is like counting, and we have very advanced technology for this (think atomic force microscopy). So now, if you put a mass on this oscillating beam, and you measure how much it’s natural frequency changed, you can calculate the mass of the object you added. This actually measures the inertial mass, but let’s not get into that.
Of course scales in your everyday scientific lab or kitchen or gold shop don’t use this technique, they use what other comments mentioned like magnetic methods.
Edit: English
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