The Importance of Leveling a Balance or Scales

It is important that the modern digital electronic scale be properly leveled on whatever is used for the weighing surface (the surface upon which the scale is placed). Quite often analytical scales are placed on what essentially is table top or shelf like work station. It is very important that this surface is vibration and draft free. Many of these surfaces are not truly flat. They may appear to be flat to the naked eye, but a level will show them to have uneven surfaces.
Almost all modern precision scales use a Bubble (or Spirit) Level to indicate the level condition. Scales usually have two adjustable legs that allow the user to level the balance. These scales have three legs in all, one of them being fixed. The triangular stance is the most stable and easiest to adjust. Some scales have four legs and all four are adjustable. These scales are much harder to level, and have a definite tendency to rock.
The level usually is circular when viewed from above, and has a circular bull’s eye to indicate a level condition when the bubble is centered in the eye. The feet of the precision scale should be adjusted in such a way as to cause the bubble to move to the center of the eye. Many users level the scale once and assume that will keep the scale level as long as it is on that same surface. However, scales frequently are moved small distances when in use or by accident. Even a small movement can cause a significant change in the scales calibration, if the surface is uneven or warped.
It is necessary that the weight vector be in line with the force restoration vector in order to achieve maximum accuracy. An angular change of 0.1 degrees (6 minutes) can create an error 2.mg in a 100.g weighing. An angular change of 1.0 degrees can create an error of 15.2mg in a 100.g weighing. A good level will allow the user to find level within three minutes of arc if he is careful and discerning.
The time spent reconfirming the level status may avoid serious errors when doing work which requires high accuracy weighing. Care should be taken that nothing is placed near the adjustable legs that might accidentally touch and turn them. If the scale is accidentally bumped the level should be checked immediately. The level itself requires zero maintenance unless it becomes dirty and, therefore, hard to read.

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