In Reply to: Sensors of Electronic balances which can weigh milligrams. posted by Koshy C Koshy on 05/17/00 at 8:01 AM:
The sensors used are typically called load cells. Load cells are manufactured in hundreds of different sizes, configurations, and capacities. Inside each load cell are strain gages (transducers) which change resistance
proportionatly when a force is applied. Typically there are 4 strain gages arranged in a wheatstone bridge configuration so that when an input voltage is applied (usually 5,10, or 15 vdc), and force is applied, a millivolt signal results in an output signal. This analog signal, in turn, is processed through the the A/D (analog to digital) converter and processor board is transmitted to the display. These strain gages can be VERY sensitive and even accurate to micrograms (1 millionth of a gram) or better.
I hope this wasn't too technical for you, as I really have not described the whole process in full. But in a nutshell, this is what happens.