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Do You Know ?
It was ancient Egypt, around 3500 b.c to which the history of balances
and scales can be traced to. In its most simplistic avatar, an equal-arm
balance on a fulcrum was used to compare two masses. History says the
Greeks were also aware of the scales as the scales can be seen often on
monuments or other works of art. It was Romans who perfected the
equal-arm balance and scale pans. They added an index and used it to
precisely weigh small objects. |
A balance gives the most precise measurement of the mass
of an object. Modern scales and balances used in the laboratory are of
course very complex having a plethora of uses. In laboratory applications of
balances range from weighing chemicals with extreme sensitivity. For a
fuller understanding of the functioning of balances and scales operate a
basic understanding of the difference between mass and weight is a must.
Mass is basically a constant unit of the quantity of matter possessed by
the object. Irrespective of the place where the measurement is taken, It
stays the same. The popular units for mass are the gram and kilogram. Coming
to Weight, it refers to an item's heaviness. Weight depends on the gravity
on the item multiplied by the mass (constant).
A common unit for weight measurement is the newton. A newton takes into
account the mass of an object as well as the relative gravity. Thus giving
the total force that is weight. Mass and weight being two distinct entities,
never the less the process to ascertain both weight and mass is called
weighing.
Balance and Scale Terms
Accuracy : Accuracy refers to a scale's ability to provide with a
result that is nearly or very close to the actual value. Modern balances
reportedly have an accuracy better than one part in 100 million for purposes
of comparing one-kilogram masses.
Calibration : Calibration is nothing but comparing of the output of
a scale or balance against a value taken as standard. Calibration is
normally done using a standard known weight and adjusted subsequently so
that reading of the instrument is in agreement.
Capacity : Capacity is the heaviest load which can be measured by
the instrument.
Precision : Precision refers to extent of agreement among repeated
measurements having identical quantity. It is also referred to as
repeatability. A scale can be extremely precise but it does not mean that it
is accurate.
Readability : Readability refers to smallest division in the scale
that can be read. The variation can range from 0.1g to 0.0000001g.
Readability assigns the number of places after the decimal point for reading
the scale.
Tare : Tare mans the process of removing a known weight of an
object. It is usually the weighing container, that is removed to zero in a
scale. Thus the final reading will be solely of the material to be weighed
and will not reflect the container's weight of the. Most balances permit
taring to its full capacity.
Linearity : Linearity means a balance's ability to respond in a
systematic manner throughout its capacity range. It should weigh within the
accepted tolerance limits throughout all the points in its capacity and not
only at the calibration points.
