Measurement With Piox S; Introduction - Flexim PIOX SM Ergänzung Zur Bedienungsanleitung

Supplement to User Manual - ENGLISH
1

Measurement with PIOX S

1.1

Introduction

The instrument PIOX S is used for determine the content of a component in a mixture. For the measured mixture, a media
data set containing the content of the component as a percentage value is stored in the transmitter. In the following, the
commonly used term "concentration" will be used for this percentage value.
According to the recommendation of the IUPAC, the content of a component in a mixture can be indicated as a concentra-
tion or as a fraction. The concentration is always the mass, the volume or the amount of substance of the component rela-
tive to the volume of the mixture. The fraction is the mass, the volume or the amount of substance of the component rela-
tive to the sum of the same physical quantities of all components of the mixture.
The type of the content measurement to be used in the present application is defined in the data set of the instrument be-
fore the set up. The unit of measurement (e.g. M%, ° Brix) is determined correspondingly.
1.1.1 Concentration Measurement
The concentration of a two-component mixture can be measured. The medium consists of the main component, mostly a
solvent, and of the measured component. The components do not have to be pure. For example, in the case of a dyestuff
dissolved in a solvent mixture, the solvent mixture is the main component and the dyestuff is the measured component.
Examples of media suitable for a concentration measurement are:
• solid component completely dissolved in a liquid (e.g. salt in water)
• solid component partly dissolved in a liquid (e.g. saturated salt solution)
• mixture of two liquids (e.g. oil and water)
• gas partly dissolved in a liquid (the concentration of the dissolved gas is measured)
• component with changing concentration (due to a chemical reaction or physical effect) in a liquid (e.g. aggregation and
change of the state of an emulsion or suspension). The change of the sound speed can be interpreted as a degree of
aggregation or conversion.
A concentration measurement is possible if the following conditions are met:
• valid parameters and calibration coefficients for the measured media are entered in the transmitter
• a temperature probe is installed
• measurement of the medium temperature (Pt100/Pt1000 or external temperature measurement) is installed in the
transmitter
The measured concentration can be stored and transmitted with the other measured values.
Measurement principle
To calculate the concentration of a medium component, the sound speed of the flowing medium is measured. As the inac-
curacies of the installation (e.g. transducer distance, pipe diameter, pipe wall thickness) have a strong effect on the mea-
sured sound speed, it has to be corrected by the following calibration polynomial:
c - corrected sound speed in m/s
c
c - measured sound speed in m/s
m
T - medium temperature in °C
K ...K - calibration coefficients
0 4
The calibration coefficients are defined directly during the installation by FLEXIM or by the customer (see example on
page 28). In most cases it is sufficient to determine K
The concentration is calculated from the corrected sound speed using an algorithm that has been defined in the program
FluxKoef.
SUPIOX-SV3-0, 2011-11-29
.
c = c + K + K T + K
c m 0 1 2
.
0
. 2 . 3 . 4
T + K T + K T
3 4
Measurement with PIOX S
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