A triple beam balance is a good way to measure mass. However, most of the time, a scale is used to measure weight, and the mass is figured out from that. The amount of matter in an object is measured by its mass. Weight is a measure of how the force of gravity affects the mass at the moment.
A triple beam balance is used to measure mass because it compares an object to one that is already known to have a certain mass. Gravitational force doesn’t change the measurement because it affects both the object and the reference object in the same way.
Digital scales are often used in research because of how accurate they are, even though weight is what is being measured.