Scales Mechanical balances are also triple beam balances like the TBB. The amount of beams doesn't affect the way the balance works, they only add increments, which in turn increases the precision. The three beam balances work on the same theory that you probably think of the classic double pane when you hear the term 'balance' first. They equate a known mass with an unknown mass, so that gravitational variations do not impact them. Each beam is fitted with a moving counterweight (a balance). In either direction you can slide the counterweight. The established mass is therefore compared with the unknown mass. The item you measure against the counterweights is therefore balanced.
Beam balances apply the concept of the lever. Anything known as a pivot is between the counterweight force and the load. "The further removed the counterweight is from the middle, the further downward it is," the Lever theory says. The counterweight does not range from 1kg to 10kg (you can think of how heavy a medical practitioners scale will be when we weighed rather than strength!); when it is getting further down, more strength is used and weight is balanced.When calibrating the balance of your beam, you effectively insure that the counterweights are as near as possible to the fulcrum if there is null. Balances of the beam are calibrated by a screw that is normally underneath the weighing tub. The counterweights shift the beam up or down, so that when correctly balanced the balance pointer moves from zero.