Measuring Principle - Anton Paar DMA 35 Betriebsanleitung

EN
• Do not leave sample/rinsing containers uncovered. Clean all spillages
immediately.
• Make sure that the setup location is sufficiently ventilated. The environment of
DMA 35 must be kept free of flammable gases and vapors.
• Supply a fire extinguisher.
3

Measuring Principle

Definition of density
The density ρ of a sample is defined as its mass divided by its volume:
m
ρ
= ---- -
V
Density is a temperature-dependent measuring unit.
The oscillating U-tube principle
The sample is introduced into a U-shaped borosilicate glass tube that is being excited
to vibrate at its characteristic frequency electronically. The characteristic frequency
changes depending on the density of the sample. Through determination of the
characteristic frequency the density of the sample can be calculated. Due to the
temperature dependency of the density value, the temperature of the sample has to
be determined precisely.
Concentration measurement
In binary mixtures, the density of the mixture is a function of its composition. Thus, by
using density/concentration tables, the density value of a binary mixture can be used
to calculate its composition.
This is also possible with so-called quasi binary mixtures. These are mixtures
containing two major components and some additional ones which are present in very
small concentrations compared to the two main components. Many decarbonated soft
drinks, for example, can be considered to be quasi binary mixtures of sugar in water
because the concentration of flavors and acids are very small compared to sugar and
water. Thus, the sugar concentration can be measured with a density meter.
12 C96IB01