ABSTRACT
Equal-arm balances are functional over a wide load range; unfortunately, the center of gravity and therefore the balance sensitivity change with load. The difference in mass between A and B will be determined by substitution weighing. However, as in the equal-arm balance example, the small mass standard A is sometimes required to calibrate the balance response. Contrary to common belief, most modern electronic force compensation balances do not require leveling. Tilt error is removed with the application of the internal calibration weight. If one views the operation performed on balance observations to derive the mass difference between nominally equal objects, one would conclude there are only two types of balances. In principle, direct weighing on the spring balance and direct weighing on a modern electronic balance are the same in that a casual observer might wonder where the mass standard is located.
