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Author:Olkkonen, Martta-Kaisa
Title:Non-destructive RF moisture measurement of bio material web
Biomateriaalirainan radiotaajuinen kosteudenmittaus ainetta rikkomatta
Publication type:Master's thesis
Publication year:2010
Pages:55 s. + liitt. 17      Language:   eng
Department/School:Radiotieteen ja -tekniikan laitos
Main subject:Radiotekniikka   (S-26)
Supervisor:Vainikainen, Pertti
Instructor:Laitinen, Tommi
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201203151572
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  1253   | Archive
Keywords:resonator
moisture measurement
non-destructive testing
belt filter press
resonaattori
kosteudenmittaus
ainetta rikkomaton testaus
suotonauhapuristin
Abstract (eng): In this Master's thesis, it is studied, whether the moisture content of a bio material web can be measured non-destructively with a sensor by means of RF waves.
The material under test is sludge from the process of a paper factory.
The sludge is dewatered in a belt filter press because it will be burnt.
The moisture content of the bio material web is of interest because the aim is to optimize energy consumption in the whole process.

A prototype sensor is built to perform test measurement both in laboratory conditions in Aalto University and finally in the factory in on-line conditions.
The chosen resonator sensor is a strip-line cavity resonator.
The frequency range over which the resonator functions is first tested with a reference material that is moistened with tap water.
The operation of the resonator is tested also with two bio material samples in the laboratory.
The operation of this resonator sensor is based on perturbation theory.

It can be estimated that the frequency shift caused by the material that is inserted in the resonator, is linear as a function of the water that the material contains.
This applies to a situation where the imaginary part of the relative permittivity is much smaller than the real part.

In the factory measurements, 65 reference samples were collected and the corresponding resonant frequency shifts were measured.
The analysis is based on the calculated equivalent thickness of the water layer.
The relative shifts of the resonant frequency as a function of the equivalent water layer of each sample are fitted to a line.
The result indicates that the standard deviation of the relative resonant frequency shift is 1.3%.
Abstract (fin): Tässä diplomityössä tutkitaan, onko ainetta rikkomaton, radiotaajuinen kosteudenmittaus mahdollista toteuttaa biomateriaalille, jolle menetelmää ei ole ennen käytetty.
Tutkittava materiaali on lietettä paperiprosessista.
Liete kuivatetaan suotonauhapuristimessa, koska aine menee poltettavaksi.
Kosteudenmäärityksen avulla on tarkoitus optimoida koko prosessin energiankulutusta.

Sekä Aalto-yliopiston laboratorio-olosuhteissa että lopulta tehtaalla suoritettavia testimittauksia varten rakennettiin prototyyppianturi.
Anturi on rakenteeltaan liuskajohdollinen onteloresonaattori.
Anturin taajuusaluetta testattiin vertailunäytteellä, joka oli kasteltu hanavedellä.
Myös biomateriaalinäytteitä testattiin laboratoriossa.
Anturin toiminta perustuu perturbaatioteoriaan.

Voidaan tehdä oletus, että resonaattoriin asetetun materiaalin aiheuttama taajuusmuutos on suoraan verrannollinen aineen sisältämään kosteusmäärään.
Oletus pätee silloin, kun suhteellisen permittiivisyyden imaginääriosa on huomattavasti pienempi kuin reaaliosa.

Tehdasmittausten aikana otettiin 65 näytettä ja vastaavat resonanssitaajuudet mitattiin anturilla.
Tulosten jatkokäsittely perustuu laskettuun ekvivalentin vesikerroksen paksuuteen.
Kunkin näytteen suhteellinen taajuuden muutos ekvivalentin vesikerroksen paksuuden funktiona sovitetaan suoralle.
Päätellään, että suhteellisen taajuuden muutoksen standardideviaatio on 1.3 %.
ED:2011-01-18
INSSI record number: 41485
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