A double-pan balance is a scale which has 2 pans that are balanced against each other. The scale functions like a see-saw, with each of the 2 pans attached to a beam over a centered pivot point.
The object to be weighed is placed on 1 pan. The other pan is gradually loaded with small weights until the scale balances, as shown by a measurement gauge reading "0." The weights are added up to get the weight of the target object.
The weights of 2 different objects can be immediately compared using a double-pan balance. An object is placed in each pan, and the heavier pan will drop while the lighter one rises. This will show which object is heavier, but it will not show the actual weights of the 2 objects.
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A double-pan balance is only as accurate as the smallest weight being used to balance the scale. If you only have 5-gram weights, you will be able to estimate the weight of the target object only to the nearest 5 grams.
A double-pan balance can also be used to determine how much of a substance makes up a specified weight. For example, if you wanted to measure 10 grams of sand, you could load 1 pan with a 10-gram weight, and then place sand in the other pan until it balances.
Take into account the weight of any container you place objects in. Weigh the empty container first and record the weight. Weigh the object and container together. Subtract the container weight from the total to get the weight of the object.