Modern balances have come a long way since the days of the knife-edge beam balance (which nevertheless still has important uses in the laboratory).
Today's digital weighing scale is (or can be) a sophisticated weighing device complete with a suite of software to record and process the results achieved during weighing. The first electronic scales appeared in the late 1960s, at which time the ability to read and display one part in 10,000 (e.g. a balance with a total capacity of 1 kg reading to 0.1g) was quite an achievement. Today it is possible to display a weight to within 1 part in several million using new weight detection systems and sophisticated electronics.
For general laboratory applications there are two basic types of electronic weight detection system in common use: the strain/ force gauge load cell and the electromagnetic force system, There are of course other equally valid systems available, such as the tuning fork, which is based on the different frequencies emitted by a tuning fork or stretched wire under different loads, and ceramic capacitance, which reads the different levels of capacitance between two plates which are being urged together under a load.