Sartorius YDK03MS Mode D'emploi page 15

Air Buoyancy
Depending on the temperature, humidity and air pressure, a 1 cm
will have a weight of around 1 .2 mg . When weighing in air, the object experiences
a corresponding buoyancy per cm
buoyancy is not allowed for shows up in the third decimal place and should therefore
be corrected .
The buoyancy force is taken into account in the following formula:
Where ρ (a) = 0 .0012 g/cm
20°C, pressure 101 .325 kPa) .
Immersion Depth
The pan for holding and/or immersing the sample during weighing in liquid is
attached rigidly to two wires and is immersed approximately 30 mm below the surface
of the liquid . Since the balance is tared prior to each measurement, the additional
buoyancy from the submerged part of the measurement setup is not factored into the
determination of the density .
When weighing in liquid, a volume of liquid corresponding to the volume of the
sample body gets displaced . This causes the fastening wires on the pan to be immersed
deeper and to generate additional buoyancy, creating an error in the density
determination .
The following formula will correct the error:
As the correction factor is determined exclusively by the geometry of the device,
it must be ensured that only the supplied vessel with the larger diameter (90 mm) is
used to determine the density of a solid object . Chapter "6 Formulas," page 23
shows how this correction factor is derived .
of its volume . The error that results if the air
3
W (a) · [ρ (fl) – ρ (a)]
ρ =
W (a) – W (fl)
= density of air under normal conditions (temperature
3
W (a) · [ρ (fl) – ρ (a)]
ρ =
0.99983 [W (a) – W (fl)]
Operating Instructions YDK03MS | YDK04MS
Operation
volume of air
3
+ ρ (a)
+ ρ (a)
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