Preconditions For Precise Measurements; Calculation Of Results; Influence Factors For Measurement Errors; Air Bubbles - KERN YDB-03 Mode D'emploi

7 Preconditions for Precise Measurements

There are numerous error possibilities during density determination.
Accurate knowledge and caution are required to achieve precise results when
applying this density set in combination with the balance.

7.1 Calculation of Results

The balance displays results for density determination by giving four or five decimal
places. However, this does not mean that the results are accurate down to the last
decimal place as this would be the case for a calculated value. Therefore all weighing
results used for calculations have to be examined closely.

7.2 Influence Factors for Measurement Errors

7.2.1 Air bubbles

A small bubble with a diameter of 1 mm results in a buoyancy of 0.5 mg, while those
with 2 mm Ø already produces a buoyancy of 4 mg.
Therefore, make sure that no air bubbles adhere on the solid object or sinker that is
immersed in the liquid.
An oily surface causes air bubbles when immersing in the liquid, so
 degrease the solvent-resistant solid sample
 clean all parts that are immersed regularly and don't touch them with bare
fingers
Don't lay solid samples (particularly flat objects) outside of the liquid on the sample
dish, because this results in air bubbles by the joint immersion.

7.2.2 Solid body sample

A sample possessing too great a volume that is immersed in liquid will result in an
increase in liquid level inside the glass pitcher. As a result, part of the suspension
bracket of the sifting bowl will also be immersed causing buoyancy to increase.
As a consequence the weight of the specimen in the liquid will drop.
Samples that change the volume or assimilate liquid are unsuitable for measurement.
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