All music directors transporting electricity produce a field of force around them called magnetic field hence increasing usage of electrical equipments means there is increased exposure to magnetic field and concerns sing wellness jeopardies due to exposure to low frequence magnetic Fieldss originate due to this ground it is of great importance to cognize about the distribution of the magnetic field in residential country. In Sweden Stralsakerhetsmyndigheten ( Swedish Radiation Safety Authority ) asked Chalmers University of Technology in Gothenburg to execute a survey in Gothenburg, Boras and Mark in order to supply the Authorities with magnetic field distribution in the houses in these countries, for this intent a entire figure of 97 houses were chosen indiscriminately in Gothenburg, Boras and Mark to mensurate the magnetic field in them.
Chiefly two types of measurings were performed in each house foremost a individual point measurings in the life room, sleeping room and kitchen in 15 different points in 3 different tallness degrees in each of the mentioned suites, so 24 hours measurings in the maestro sleeping room.Finally the readings from both measurings were combined and a net value for the mean magnetic field in each place was calculated based on the consequences of this survey 90 % of these houses had an mean magnetic field in the scope 0-0.2 AµT. Beside this consequences it was besides aimed in this survey to include some information sing harmonics organizing the magnetic field in each house and include some information about the entire harmonic deformation ( THD ) . It was seen that most of the houses have high values of THD. It was besides seen that the largest constituent of the magnetic field comes for the harmonics at the 50 Hz frequence. Finally it was observed that the magnetic field has its highest value at the underside of each room.
This thesis work is aimed to give a distribution of the magnetic field of houses in Gothenburg, Boras and Mark in Sweden.
In chapter1 magnetic field and different beginnings of magnetic field are introduced so electromagnetic spectrum is analyzed and wellness jeopardy associated with non ionising portion of the spectrum are reviewed.
In chapter2 methods used in this survey for mensurating the magnetic field are described every bit good as the instruments used for the measuring intent so at the terminal different measuring prosodies used in survey to show the consequences are explained
In chapter 3 consequences of this survey are presented. As the concluding end of this survey a Comulative distribution map ( CDF ) is represented which shows how much per centum of the houses are below a certain magnetic field degree.
In chapter 4: a treatment on the concluding consequences is held
In this chapter it is aimed to supply the reader with the definition of the chief constructs used in this survey and beside explain the importance of carry oning this survey.
1.1 Magnetic Field
Magnetic field is defined as “ a field of force produced by movingA electric charges or byA simple particlesA that possess their ain ‘intrinsic ‘ magnetic field, a relativistic consequence which is normally modeled as aA spinA of the atom ” [ 1 ] .
Among different beginnings indicated in former definition of the magnetic Fieldss in this survey we are interested in the magnetic Fieldss produced by music directors transporting electricity.
Magnetic Fieldss caused by electrical currents as depicted in figure 1.1 occur in uninterrupted closed waies around the currents bring forthing them hence a music director transporting electrical current gives rise to a magnetic field, the strength of this magnetic field is ever relative to the current in the music director and the distance from the music director. To demo the Magnetic Fieldss normally field lines are used and the magnetic field strength is changeless along the music director in closed waies around the music director. In the instance of other beginnings, magnetic Fieldss tend to hold a complicated visual aspect which normally can non be calculated but have to be measured alternatively. The unit used to mensurate the magnetic flux denseness is called the tesla [ T ] . Based on the earlier definitions magnetic Fieldss can be caused by electrical devices and installing overseas telegrams. In certain instances, isolated currents can give rise to magnetic Fieldss. In Sweden, since the electricity system frequently contains four music directors taking to each edifice, isolated currents can ensue in major jobs. [ 2 ] “ The decay current can go through through the impersonal music director as intended, but it can besides go through through the Earth music director and into the plumbing pipe work to the transformer ‘s Earth point. This increases the magnetic field both along the way of the isolated current and along the supply overseas telegram.
Straight music director
Figure 1.1.Magnetic field around a wire transporting electrical current.
Power lines are besides considered as a major external beginning of magnetic field. The stage current is bring forthing the magnetic field caused by power lines. “ Near to power lines magnetic flux can make to a upper limit of 10 to 30 I?T but at a distance of 50 to 200 metre it decreases to less than 1 I?T ” [ 3 ] .
Magnetic field at places and working environments come from both external and internal beginnings, typical external beginnings are power lines, power distribution substations near to residential subdivisions and even H2O pipes transporting imbalanced neutrals current while internal beginnings are the families contraptions.
As it was mentioned earlier It comes from the definition of the magnetic field that electrical current is capable of bring forthing magnetic field hence increasing usage of electrical equipments means there is increased exposure to magnetic field and concerns sing wellness jeopardies due to exposure to low frequence magnetic Fieldss arises hence International Commission on Non-Ionizing Radiation Protection ( ICNIRP ) [ 10 ] was established to look into the jeopardies associated with exposure to non ionising radiation ( NIR ) and develop guidelines on NIR exposure. ICNIRP is sing acute wellness effects that may for illustration lead to the stimulation of the nervousnesss. Among all guidelines introduced by ICNIRP there are guidelines for restricting clip changing electric and magnetic Fieldss ( EMF ) exposure. ICNIRP guidelines in this respect come in two in two major classs [ 10 ] .
Occupational exposure [ 10 ] .
General public exposure [ 10 ] .
Occupational guidelies consider the expousure of the workers to clip changing electric and magnetic Fieldss at their workplace while general public guidlines see all people of the society in all ages exposed to clip changing electric and magnetic Fieldss even in instances they are no aware of being exposed to magnetic Fieldss [ 10 ] .
mention degrees for general public exposure and occupational exposure by ICNIRP are summerized in table 1 and table 2 [ 10 ] .
Frequency scope magnetic flux denseness B ( T )
1 Hz-8 Hz 4A-10-2 /f2
8 Hz-25 Hz 5A-10-3 /f
25 Hz-50 Hz 2A-10-4
50 Hz-400 Hz 2A-10-3
400 Hz-3KHz 8A-10-3 /f
3 KHz-10M Hz 2.7A-10-5
Table 1.General public exposure guidelines by ICNIRP.
Frequency scope magnetic flux denseness B ( T )
1 Hz-8 Hz 0.2/f
8 Hz-25 Hz 2. 5A-10-3 /f
25 Hz-300 Hz 1A-10-3
300 Hz-3 KHz 0.3 /f
3 KHz-10M Hz 1A-10-5
Table 1.Occupational exposure guidelines by ICNIRP.
1.2. Health Hazards Associated with Exposure to Low Frequency Magnetic Field
The electromagnetic spectrum includes ionizing, optical and non-ionizing radiation. The non-ionizing radiation is in the frequence scope from 0 Hz up to 300 GHz. The energy of the non-ionizing radiation is non strong plenty to interrupt the chemical bonds of familial molecules nevertheless there are some biophysical mechanisms that can take to inauspicious wellness effects. For low frequences the mechanism is stimulation of nervousnesss and cell due to initiation of current. For higher frequence ranges the mechanism will be tissue heating [ 4 ] .
“ Highly low frequence magnetic Fieldss are besides classified possible carcinogenic. Epidemiologic surveies systematically are demoing an association between long-run mean exposure to magnetic Fieldss above 0.3/04 I?T and childhood leukaemia malignant neoplastic disease ” [ 4 ] .
In the approaching subdivision some wellness jeopardies related to exposure to low frequence magnetic Fieldss are reviewed based on some major surveies.
Childhood Leukemia and Magnetic field Exposure in Ontario, Canada.
In a instance control survey including 88 instances consisting incident leukaemia at 0-14 old ages of age and 133 controls an association between magnetic field exposure and increased hazard of leukaemia was observed [ 5 ] .
Childhood Leukemia and Magnetic field Exposure in Japan
Power frequence magnetic field is labeled as a possible carcinogen by the International Agency for Research on malignant neoplastic disease panel. In Japan one of the high exposure countries of the universe a population-based case-control survey was performed. This survey covered countries with 54 % of the Nipponese kids. 312 instance kids between 0-15 old ages old with acute leukaemia and 603 controls matched for gender, age and residential country were analyzed. magnetic field mean was measured in each kid house the survey showed that most of the leukaemia instances were exposed to magnetic field degrees far above 0.4 I?T. [ 6 ]
Exposure to Magnetic Fields during Pregnancy and the Hazard of Miscarriage.
In a survey performed in San Francisco 969 pregnant adult females all with a positive gestation trial at less than 10 hebdomads of gestation and all the adult females were shacking in San Francisco. The result consequences were tested utilizing the wellness care organisation databases. Although no association was observed between abortion hazard and the mean magnetic field degree, abortion additions with an increasing degree of maximal magnetic field exposure with a threshold around 1.6 AµT [ 7 ] .
This all shows it is of great importance to cognize about the distribution of the magnetic field in the residential countries. The methods used to supply such a graph demoing this distribution are explained in the following chapter.
In the old chapter the wellness jeopardies associated with exposure to low frequence magnetic Fieldss were discussed and based on several surveies mentioned in the same chapter. Magnetic Fieldss above a certain degree might be considered as a possible menace to inhabitants overall wellness in residential countries therefore it is of great importance to cognize about the distribution of magnetic Fieldss in residential countries.
In Sweden Stralsakerhetsmyndigheten ( Swedish Radiation Safety Authority ) asked Chalmers University of Technology in Gothenburg to execute a survey in Gothenburg, Boras and Mark in order to supply the Authorities with magnetic field distribution in the houses of these country.
In this chapter methods for supplying such a distribution are described every bit good as instruments used for measurement intent. Wholly 97 houses in Gothenburg, Boras and Mark in Vastergotland were capable of this survey. All the houses were chosen indiscriminately to cover all the residential countries in the mentioned countries.
It was explained in the first chapter that magnetic Fieldss tend to hold a complicated visual aspect which normally can non be calculated, but have to be measured. Five different instruments were used in this survey, a short description of each one beside its application in this survey is given in this subdivision.
2.1.1. Envirometor ML-1
Figure 2.1. Enviromentoir ML-1 magnetic field lumberman.
This instrument is capable of mensurating RMS value of the magnetic Fieldss in X, Y and Z way irrespective of the way in which the instrument is indicating in relation to the magnetic field. This instrument is able to hive away the measuring informations in a logging footing with logging intervals runing from 1 2nd to 150 seconds and wholly the instrument can hive away up to 8,192 readings. The stored informations can be transferred to a computing machine utilizing the Rs232 connexion so the Personal computer package attach toing the instrument will supply the user with mean of stored readings
Maximum and lower limit of stored informations, standard divergence, average and eventually high and low one-fourth.
A figure of studies and graphs can besides be generated utilizing this Personal computer package. Ml-1 frequence scope is 30Hz-2kHz. In this survey we used ML-1 for 24 hours logging in the sleeping rooms with logging intervals equal to 40 seconds. However in the houses near the railroads this instrument could non be used for 24 hours logging since trains in Sweden are bring forthing a dominant magnetic field in 16 Hz and ML-1 due to its internal set base on balls filter get downing at 30 Hz can non mensurate this major constituent hence due to this hardware restriction for houses near the railroads this instrument was non suited and another instrument Combinova MFM10 was used. In the following page an illustration of a study generated by ML-1 PC package is shown.
Figure 2.2.Intensity distribution of magnetic field from Enviromentor ML-1.
In this study every bit good as the strength distribution of the logging informations some other statistical information like Min, Max, Mean, Median, Standard divergence, Low quart and High Quart are given.
2.1.2. Combinova MFM10
Figure 2.3. Combinova MFM10 magnetic field logger.MFM10 is capable of individual point measurings of the magnetic field. It can every bit good be used for logging measurings. The frequence scope MFM10 covers is between 5-2000 Hz. Since this frequence scope covers the 16 Hz frequence it was used for 24 hours logging of the houses in the locality of railroads alternatively of Enviromentor ML-1. The 16 Hz magnetic field constituent generated by trains which is a major constituent that Enviromentor ML-1 is unable to mensurate due to its hardware restrictions will be taken into history utilizing this instrument. Stored readings From CombinovaMFM10 are transferred to computing machine utilizing RS232 overseas telegram as a text file. The logging interval used for MFM10 is 60 seconds. A typical image of this instrument is show in figure 2.3.
2.1.3. MFM 3000
Figure 2.4. Combinova MFM 3000 magnetic field loggerThis instrument, as depicted in figure 2.4 is used for individual point measurings. MFM 3000 is an advanced instrument that besides giving the entire RMS value for the magnetic field it besides provides user with the largest and 2nd largest frequence constituents of the entire RMS value. The frequence coverage of this instrument is from 5 Hz up to 400 KHz. However this instrument gives the user the possibility to contract this frequence scope. In the instance of these survey frequencies up to 10 Hz were filtered to cut down the signals due tomeasurments in the earth magnetic field.
Before executing any measurings all the instruments used in this survey were calibrated. A standardization trial was performed in Stralsakerhetsmyndigheten ‘s research lab to see if they were all to the full functional and step true values for the magnetic field. For this intent a set up including a Helmholtz spiral bring forthing magnetic field was used The magnetic field created in the centre of spiral was calculated so all the instruments were placed in the centre of the spiral to see if they were mensurating the expected value or non. This set up includes four chief parts
Signal generator ( SPN ) ( 1Hz -1.3MHz )
Amplifier ( gain 16.1 for burden of 5 ohm )
Resistor to mensurate the current ( 3.3 ohm, 1 ohm )
Helmhotz spiral ( dimension of the box is 56×79 )
These five parts were conected based on the schem dipicted in figure 2.5.
Figure 2.6. Calibration Apparatus
Signal generator was connected to the Amplifier and so to the opposition. Finally the spiral was conected to the other parts to the spiral. .
The expression AµT was used to cipher the magnetic field produced by the spiral at its centre ; therefore the electromotive force was set to 0.581883v so based the former equation all the instruments were supposed to mensurate a magnetic field of 1 AµT ( RMS ) at the centre of the spiral.
2.3. Measurement Prosodies
It was mentioned earlier that the intent of this survey is chiefly to hold the distribution of the magnetic field in houses in Gothenburg, Boras and Mark and a entire figure of 97 houses were indiscriminately chosen for this end and a figure of prosodies have been defined to be express the measuring consequences from each of these house. In this portion a short description of each of these prosodies is given so processs for informations acquisition are given in the undermentioned subdivision.
2.3.1. Adjusted Average:
Two types of measurings are performed in this survey one is individual point measuring and the other one is the 24 hours logging. For individual point measurings Combinova MFM 3000 is used and the individual point measurings are performed in the life room, kitchen and sleeping room harmonizing to the strategy depicted in figure 2.7 in which for each room the magnetic field is measured in the four corners of the room and the centre in three different tallness degrees. For 24 hr logging either Enviromentor ML-1 or Combinova MFM10 are used therefore we need a alone expression to cipher the mean magnetic field of the house based on the reading of both instruments. In order to give such a expression two constructs are taken into consideration, first one is the mean exposure of the people in house that requires a leaden norm expression based on the mean clip people spend in each room, 2nd is the mean magnetic field of the house that is a normal norm. The expression for ciphering the mean magnetic field that people in each house are exposed to is called Badjust and it is calculated from the following values. It is assumed that people on mean spend 9 hours in the sleeping room 2 hours in the kitchen and 4 hours in the life room so the leaden mean expression can be calculated as follow
Bbed = 24 h norm from the measuring point at the bed.
BsleepR = Room norm for kiping room.
Bkitchen = Room norm for kitchen
BlivingR = Room norm for life room
3 suites: Badjust =
2 suites: Badjust =
1 room: Badjust = Bbed.
Figure ( 2.7 ) : individual point measurings strategy
2.3.2. Entire Harmonic Distortion ( THD )
To hold a better underestanding of the THD we refre to Wikipedia
“ To understand a system with an input and an end product, such as an sound amplifier, we start with an ideal system where the transportation map is additive and time-invariant. When a signal passes through a non-ideal, non-linear device, extra content is added at the harmonics of the original frequences. THD is a measuring of the extent of that deformation.
When the input is a pure sine moving ridge, the measuring is most normally the ratio of the amount of the powers of all higher harmonic frequences to the power at the first harmonic, or cardinal, frequence:
Which can equivalently be written as
Measurements based on amplitudes ( e.g. electromotive force or current ) must be converted to powers to do add-on of harmonics deformation meaningful. For a electromotive force signal, for illustration, the ratio of the squares of the RMS electromotive forces is tantamount to the power ratio:
where Vn is the RMS electromotive force of n-th harmonic and n=1 is the cardinal frequence.
THD is besides normally defined as an amplitude ratio instead than a power ratio, [ 1 ] ensuing in a definition of THD which is the square root of that given above:
This latter definition is normally used in audio deformation ( per centum THD ) specifications. It is unfortunate that these two conflicting definitions of THD ( one as a power ratio and the other as an amplitude ratio ) are both in common use. The power THD can be higher than 100 % and is known as IEEE, but for audio measurings 100 % is preferred as upper limit, therefore the IEC version is used ( used by Rohde & A ; Schwartz, Bruel and Kj?r ) .
Measurements for ciphering the THD are made at the end product of a device under specified conditions. The THD is normally expressed in per centum as deformation factor or in dubnium as deformation attenuation. ” . [ 8 ]
Based on the former subdivision from Wikipedia there are two different definitions, nevertheless in this survey the power definition ( IEEE ) is used
Measuring the amplitudes of the B-field from MFM 3000 we get
Figure 2.7. A typical measurment on Combinova MFM 3000 show.
Here Ptotal is relative to
P1 is relative to ( the square of the largest signal )
Therefore the THD = %
Frequency of the 2nd largest signal:
At each house there are 15 measurement values in each room and up to 3 suites ( Bed room, living room and kitchen ) are measured.
The THD for each measuring point ( up to 45 values ) is calculated and so the mean THD is calculated
THD Average =
Where THD1 = is the THD for the first measuring point in that house aˆ¦and THDn is the last measuring point in that house.
For the frequence of the 2nd largest signal the most frequent value of the n measurings is chosen nevertheless Due to FFT some inexact frequences can look, values from 149 to 151 Hz are rounded to 150 Hz and values around 16 – 18 Hz are rounded to 16.7 Hz ( train frequence ) .
However in some instances some struggles may originate so some regulations are set for computation of the THD. These regulations are listed below.
If L.S. & gt ; RMS put THD = 0. ( If L.S. is considerable & gt ; RMS so in informations must be incorrect, seek to rectify indata, if informations ca n’t be corrected so do n’t utilize this information for any computations ( THD and B adjust, degrees etc ) )
If L.S. = 0 so do non cipher THD and do n’t see it in the mean THD.
If L.S. is non 50 Hz do non cipher THD and do n’t see it in the mean THD.
If 2nd L.S. is non 0 or 150 Hz do non cipher THD and do n’t see it in the mean THD.
If L.S. & lt ; 30 National Trusts do non cipher THD and do n’t see it in the mean THD.
2.3.3. William claude dukenfields Highest on Level
The RMS readings for the 3 degrees ( floor, in-between or top ) measured in the house are compared therefore there will be up to 15 consequences for the different places. In each place the highest field can be at degree: floor, in-between, top or none ( if the measuring values are the same for the two or three highest values ) . Numbers of highest degree at “ floor ” , “ center ” , “ top ” or “ none ” are calculated so the most frequent one is chosen. If the Numberss of the most frequent degree is shared with more than one degree, so “ none ” is chosen. However for floor totaling two methods are used based on Wikipedia
“ Floor enumeration is the numbering strategy used for a edifice ‘s floors. There are two major strategies in usage across the universe. In one system, used for case in the British Isles, the floor merely above the land floor is assigned the figure 1 ( or “ first ” ) ; in the other system, used in the United States, that same floor is figure 2 ( or “ 2nd ” ) . In both systems, the enumeration of higher floors continues consecutive as one goes up, as shown in the undermentioned tabular array:
Supplanting from land degree
3 narrative highs above land
“ 3rd floor ”
“ fourth floor ”
2 narrative highs above land
“ 2nd floor ”
“ 3rd floor ”
1 narrative height above land
“ 1st floor ”
“ 2nd floor ”
at land degree
“ Land floor ”
“ Land floor ” or “ 1st floor ”
In this survey the British Scheme is used. ” [ 9 ]
2.4. Data Acquisition Procedures:
In this subdivision procedures for informations acquisition and besides informations certification are described. All the instruments are capable of hive awaying readings and through their Personal computer package they transfer informations to a Personal computer. Beside these computerized stored informations a cheque list was used every bit good for manual certification of informations. Besides readings from the instruments some extra information sing each house like house type ( if it is a Villa or an flat ) and its location ( if it is close railroads or non ) were documented on a hardcopy. An illustration of list for manual certification of the information is shown in figures 2.8 and 2.9. beside references and contact info a alone codification was besides assigned to each house therefore the difficult transcripts and softcopies were match easy with an anon. pod and after sharing the measuring informations between group members over internet participants privateness was reserved since there is nil sing the individuality of the participants over cyberspace and they are all called with a alone silent person pod. Due to privacy grounds the method for coevals of alone pods is non explained here.
Figure 2.9. Typical checklist Used in this survey.
In the first page of this cheque list as it is shown in figure 2.9 basic information like the house type, figure of floors and its location if it is close railroads or non are filled out so information sing the 24 hours logging are filled out eventually a little secret plan of the sleeping room is given with major magnetic field beginnings if there is any in the room. In the following pages of the checklist as depicted in figure 2.10 individual point measurings from MFM 3000 are filed out and a simple secret plan of that room with the major magnetic field beginnings is included.
Figure 2.9. Checklist used for individual point measurings.
In the old chapter methods for mensurating the magnetic field were described in inside informations so a figure of prosodies introduced to stand for the magnetic field measurments matching to each house. The concluding end of this chapter is to demo how much per centum of the houses are below a certain value for the magnetic field, meanwhile some single graphs and values for some houses with certain belongingss are given.
3.1.24 Hours Measurements Using Combinova ML-1
As it was explained before for 24 hours measurings of the magnetic field in the houses non in the locality of the railroads ML-1 was used in the maestro sleeping room. Here two illustrations for the distribution of the magnetic field in the sleeping room for 24 hours logging are given. Figure 3.1 belongs to a Villa house in Boras and figure 3.2 belongs to an flat in Boras.
Figure 3.1. Magnetic field distribution of a typical house in Boras after 24 hours logging in the maestro sleeping room.
Figure 3.2. Magnetic field distribution of a typical house in Boras after 24 hours logging in the maestro sleeping room.
3.2. 24 Hours Measurements Using MFM10
AverageHouses in the locality of the railroads are exposed to magnetic field at 16.7 Hz since Enviromentor ML-1 rejects the magnetic constituents below 30 Hz another instrument Combinova MFM10 for 24 hours measurings in the maestro sleeping room was used. This instrument creates a text file including the logging informations, in figure 3.3 portion of such a file for a house in Mark is given. The logging interval is set to 60 seconds and the instrument automatically calculates the mean value of the logging informations for every 30 proceedingss, nevertheless it rejects informations that are excessively far from the scope of other informations during each 30 proceedingss.
Figure 3.3. Part of a text file from MFM10 incorporating 24 logging informations.
An illustration of a house near railroads holding high values over 24 hours is given in figure 3.4. This house comprises the mean magnetic field of 0.003 I?T in the sleeping room over 24 hours logging and the adjusted magnetic field norm of 0.08 I?T from both 24 hours logging in the sleeping room and individual point measurings in other suites. THD is besides 3.6. In contrast to calculate 3.4 an illustration of a house near railroads holding high values over 24 hours is present in figure 3.5. This 2nd house comprises the mean value of 0.51 I?T for 24 hours logging in the sleeping room and 0.39 for the adjusted norm as explained earlier. THD for this 2nd house is 257.2 % . Reviewing these two illustrations and detecting their relevant distribution figures for 24 hours logging in the sleeping room in the following page, reader can hold a ocular apprehension of the difference with the mentioned values.
Figure 3.4.A house near railroads holding typical values for magnetic field over 24 hours logging.
Figure 3.5. A house near railroads holding high values for magnetic field over 24 hours logging.
3.3. Single Point Measurements Using MFM 3000
Single point measurings are all performed utilizing MFM 3000 instrument in 15 different points at three different highs in up to three suites for each house. Distribution values of magnetic field for all these 15are shown in figure 3.6 and figure 3.7 these graphs are coming from the same house for which the 24 hours logging graph from ML-1 were represented in figure 3.1 and 3.2.
Figure 3.6.Single point measurings for a Villa in 45 different individual points of life room, kitchen and maestro sleeping room.
Figure 3.7. Single point measurings for an flat in 45 different individual points of life room, kitchen and maestro sleeping room.
3.4. Concluding Consequences:
Concluding consequences are given in five different parts the first subdivision includes a Accumulative Distribution Function ( CDF ) that shows how much per centum of the houses are below a certain magnetic field for the full house ( adjusted norm from both 24 hours logging in sleeping room and individual point measurings in all room ) . In figure 3.7 this graph is represented.
Figure ( 3.8 ) : Accumulative distribution map demoing how much per centum of houses are below a certain value for the magnetic field coming from both individual point measurings and 24 hours logging
This graph shows that 90 % of the houses have the adjusted mean magnetic field ( from both individual point measurings and 24 hours logging ) in the scope 0-0.2I?T. in the following graph in figure 3.9 the CDF graph from mean value of the magnetic field in the sleeping room over 24 hours logging is given.
Figure ( 3.9 ) : Accumulative distribution map demoing how much per centum of houses are below a certain value for the magnetic field coming merely from 24 hours logging in the sleeping room
The 3rd subdivision shows the THD value in a saloon graph demoing figure of houses with a certain THD value this graph is depicted in figure 3.10.
Figure ( 3.10 ) saloon graph demoing figure of houses with a certain magnetic field value
This graph shows that most houses have high value for THD. The cumulative distribution map ( CDF ) for THD is besides given in figure 3.11 However after making individual point measurings in a figure of houses and having unusual values for the THD frequencies up to 10 Hz were filtered to reject the effects of noise and better the THD values in figure 3.11 CDF graph for THD in the houses that this 10 Hz filter was included is given it is apparent that the THD value is improved.
Figure ( 3.11 ) CDF for THD
Finally in the last portion in a graph in figure 3.12 it is shown how much per centum of the houses have the highest magnetic field in each degree as explained in chapter two. It comes from this graph that most houses have the highest value for the magnetic field on the land degree
Figure ( 3.13 ) : Bar graph demoing per centum of the houses with highest magnetic field in each degree
In the appendix a drumhead tabular array including consequences for all 97 houses is given.
It is aimed in this chapter to hold a treatment over the consequences of this survey. This survey shows that 90 % of the houses have the magnetic value in the scope between 0-0.2 AµT which is sensible harmonizing the surveies over the wellness jeopardies associated with exposure to low frequancy magnetic Fieldss. nevertheless this value is non the net magnetic field for the house but it comes from a leaden norm demoing the mean magnetic field exposed to people in the houses based on the mean hours people spend in each room. This survey besides tried to give some information sing the harmonics organizing the entire RMS and it was seen that the largest constituent is in the 50 Hz that demonstrates the magnetic field in low frequences is chiefly coming from the power lines. However the entire harmonic deformation THD has some unnatural values and at the get downing it was thought this can be a consequence of the noise or shaking of the instrument and a 10 Hz filter was applied to reject frequences up to 10 Hz and consequences were improved. In the the figure 4.1 CDF for THD befor appling the 10 Hz filter is represented and comering it with the CDF of the THD after using 10 Hz filter.
Spectrum of these individual point measurings could be a utile tool to delve more into inside informations and seek for the grounds of such unusual values for THD unluckily the MFM 3000 did non hold this possibility to hold the FFT of all individual point measurings but it calculates the FFT of the last measurings but in this survey the FFT values were all zero so this could be due to some jobs with the instrument.
It was observed every bit good that in bulk of the instances the largest signal in the harmonics is at 50 Hz and the 2nd largest signal is at 0 H.