SIST EN 14253:2004+A1:2009
(Main)Mechanical vibration - Measurement and calculation of occupational exposure to whole-body vibration with reference to health - Practical guidance
Mechanical vibration - Measurement and calculation of occupational exposure to whole-body vibration with reference to health - Practical guidance
This European Standard provides guidelines for the measurement and evaluation of whole-body vibration at the workplace. This European Standard describes the precautions to be taken to make representative vibration measurements and to determine the daily exposure time for each operation in order to calculate the daily exposure value standardized to an 8 h reference period. This European Standard provides a means to determine the relevant operations that should be taken into account when determining the vibration exposure. This European Standard applies to situations where people are exposed to whole-body vibration at the workplace, transmitted through the buttocks for a seated person or through the feet for a standing person. This European Standard is restricted to the evaluation of exposure to whole-body vibration using quantities derived from frequency-weighted root-mean-square acceleration. The frequency range considered is 0,5 Hz to 80 Hz. Where the vibration includes shocks or impacts, methods in this European Standard may underestimate the severity of the exposure. There is a need to assess the risks arising from exposure to whole-body shocks and high crest factor vibration. Methods for this are beyond the scope of this European Standard.
Mechanische Schwingungen - Messung und rechnerische Ermittlung der Einwirkung von Ganzkörper-Schwingungen auf den Menschen am Arbeitsplatz im Hinblick auf seine Gesundheit - Praxisgerechte Anleitung
Diese Europäische Norm enthält Anleitungen zur Messung und Bewertung von Ganzkörper-Schwingungen am Arbeitsplatz.
Diese Europäische Norm beschreibt die zu treffenden Vorkehrungen, um repräsentative Schwingungs¬messungen durchzuführen und die tägliche Einwirkungsdauer jeder Tätigkeit zu ermitteln, um daraus die Tages-Schwingungsbelastung, normiert auf eine Bezugsdauer von 8 h, zu errechnen. Diese Europäische Norm stellt Mittel zur Bestimmung der relevanten Tätigkeiten zur Verfügung, die bei der Ermittlung der Schwingungs¬belastung einbezogen werden sollten.
Diese Europäische Norm gilt für Situationen, in denen am Arbeitsplatz Ganzkörper-Schwingungen auf Bedienungspersonen beim Sitzen über das Gesäß oder beim Stehen über die Füße übertragen werden.
In dieser Europäischen Norm wird die Einwirkung von Ganzkörper-Schwingungen nur mit solchen Größen beschrieben, die aus dem Effektivwert der frequenzbewerteten Beschleunigung abgeleitet sind. Der betrachtete Frequenzbereich beträgt 0,5 Hz bis 80 Hz. Wenn die Schwingungseinwirkung stoß- oder impulshaltig ist, liefern die Verfahren nach dieser Europäischen Norm in der Regel einen zu kleinen Wert für die Schwingungsintensität. Es sind dann Verfahren zur Beurteilung der Risiken bei der Einwirkung von Stößen und Ganzkörper-Schwingungen mit hohem Scheitelfaktor notwendig. Solche Verfahren werden aber in dieser Euorpäischen Norm nicht benutzt.
Vibrations mécaniques - Mesurage et calcul de l'effet sur la santé de l'exposition professionnelle aux vibrations transmises à l'ensemble du corps - Guide pratique
La présente norme européenne fournit des principes directeurs pour le mesurage et l’évaluation des vibrations transmises à l’ensemble du corps sur le lieu de travail.
La présente norme européenne décrit les précautions à prendre pour effectuer des mesurages de vibrations représentatifs et déterminer la durée d’exposition quotidienne pour chaque opération, afin de calculer la valeur d’exposition quotidienne équivalente pour une période de référence de 8 heures. Elle offre un moyen de déterminer les opérations correspondantes qu’il convient de prendre en compte lors de la détermination de l’exposition aux vibrations.
La présente norme européenne s’applique aux situations où des personnes sont exposées à des vibrations transmises à l’ensemble du corps sur le lieu de travail, transmises par le séant pour les personnes assises ou par les pieds pour les personnes debout.
La présente norme européenne se limite à l’évaluation de l’exposition aux vibrations transmises à l’ensemble du corps utilisant des grandeurs dérivées de l’accélération efficace pondérée en fréquence. La gamme de fréquences considérée est comprise entre 0,5 Hz et 80 Hz. Lorsque les vibrations comprennent des chocs ou des impacts, les méthodes de la présente norme européenne peuvent sous-estimer la gravité de l’exposition. Il est nécessaire d’évaluer les risques engendrés par l’exposition à des chocs et des vibrations à facteur de crête élevé transmis à l’ensemble du corps. Ces méthodes d’évaluation ne relèvent pas du domaine d’application de la présente norme européenne.
Mehanske vibracije - Merjenje in računsko ugotavljanje učinkov na zdravje oseb, ki so na delovnem mestu izpostavljene tresenju celotnega telesa - Praktično navodilo
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Mechanische Schwingungen - Messung und rechnerische Ermittlung der Einwirkung von Ganzkörper-Schwingungen auf den Menschen am Arbeitsplatz im Hinblick auf seine Gesundheit - Praxisgerechte AnleitungVibrations mécaniques - Mesurage et calcul de l'effet sur la santé de l'exposition professionnelle aux vibrations transmises à l'ensemble du corps - Guide pratiqueMechanical vibration - Measurement and calculation of occupational exposure to whole-body vibration with reference to health - Practical guidance13.160Vpliv vibracij in udarcev na ljudiVibration and shock with respect to human beingsICS:Ta slovenski standard je istoveten z:EN 14253:2003+A1:2007SIST EN 14253:2004+A1:2009en,fr,de01-februar-2009SIST EN 14253:2004+A1:2009SLOVENSKI
STANDARD
SIST EN 14253:2004+A1:2009
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14253:2003+A1
November 2007 ICS 13.160 Supersedes EN 14253:2003 English Version
Mechanical vibration - Measurement and calculation of occupational exposure to whole-body vibration with reference to health - Practical guidance
Vibrations mécaniques - Mesurage et calcul de l'effet sur la santé de l'exposition professionnelle aux vibrations transmises à l'ensemble du corps - Guide pratique
Mechanische Schwingungen - Messung und rechnerische Ermittlung der Einwirkung von Ganzkörper-Schwingungen auf den Menschen am Arbeitsplatz im Hinblick auf seine Gesundheit - Praxisgerechte Anleitung This European Standard was approved by CEN on 1 September 2003 and includes Amendment 1 approved by CEN on 21 October 2007.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36
B-1050 Brussels © 2007 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14253:2003+A1:2007: ESIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 2 Contents Page Foreword.3 Introduction.4 1 Scope.5 2 Normative references.5 3 Terms and definitions.5 4 Quantities to be evaluated.6 5 Preparation of the measurement procedure.6 6 Measurement of vibration.10 7 Measurement uncertainty.13 8 Calculation of the daily vibration exposure.15 9 Information to be reported.15 Annex A (informative)
Examples of the calculation of daily vibration exposure.17 Annex B (informative)
Some numerical examples of the determination of daily vibration exposure.19 Annex C (informative)
!!!!Guidance on handling of transient acceleration artefacts due to intentional operator movements.21 Bibliography.24 SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 3 Foreword This document (EN 14253:2003+A1:2007) has been prepared by Technical Committee CEN/TC 231 “Mechanical vibration and shock”, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2008, and conflicting national standards shall be withdrawn at the latest by May 2008. This document supersedes EN 14253:2003. This document includes Amendment 1, approved by CEN on 2007-10-21. The start and finish of text introduced or altered by amendment is indicated in the text by tags !". Users of this EN, prepared in the field of application of Article 137 (formerly 118a) of the EC Treaty, should be aware that standards have no formal legal relationship with Directives which may have been made under Article 137 of the Treaty. In addition, national legislation in the Member states may contain more stringent requirements than the minimum requirements of a Directive based on Article 137. Information on the relationship between the national legislation implementing Directives based on Article 137 and this EN may be given in a national foreword of the national standard implementing this EN. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 4 Introduction Occupational exposure to whole-body vibration can, in some circumstances, contribute to illness. The general requirements for measuring and evaluating whole-body vibration exposure are specified in ISO 2631-1. The aim of this European Standard is to provide practical guidelines to develop an effective strategy for evaluation of whole-body vibration exposure at the workplace. The use of the strategy described in this European Standard will lead to a realistic picture of the daily exposure of a subject and of the relevant uncertainties. The evaluation of vibration exposure can be broken up into a number of different stages: identifying a series of discrete operations which make up the subject's working pattern; selection of operations to be evaluated; establishing the r.m.s. acceleration value for each selected operation; evaluation of a typical daily exposure time for each operation identified; calculating the daily vibration exposure. SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 5 1 Scope This European Standard provides guidelines for the measurement and evaluation of whole-body vibration at the workplace. This European Standard describes the precautions to be taken to make representative vibration measurements and to determine the daily exposure time for each operation in order to calculate the daily exposure value standardized to an 8 h reference period. This European Standard provides a means to determine the relevant operations that should be taken into account when determining the vibration exposure. This European Standard applies to situations where people are exposed to whole-body vibration at the workplace, transmitted through the buttocks for a seated person or through the feet for a standing person. This European Standard is restricted to the evaluation of exposure to whole-body vibration using quantities derived from frequency-weighted root-mean-square acceleration. The frequency range considered is 0,5 Hz to 80 Hz. Where the vibration includes shocks or impacts, methods in this European Standard may underestimate the severity of the exposure. There is a need to assess the risks arising from exposure to whole-body shocks and high crest factor vibration. Methods for this are beyond the scope of this European Standard. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. !EN ISO 8041, Human response to vibration - Measuring instrumentation (ISO 8041:2005)" EN 30326-1, Mechanical vibration — Laboratory method for evaluating vehicle seat vibration — Part 1: Basic requirements (ISO 10326-1:1992) ISO 2631-1, Mechanical vibration and shock — Evaluation of human exposure to whole-body vibration — Part 1: General requirements ISO 5347 (all parts), Methods for the calibration of vibration and shock pick-ups ISO 5348, Mechanical vibration and shock — Mechanical mounting of accelerometers ISO 16063 (all parts), Methods for the calibration of vibration and shock transducers 3 Terms and definitions For the purposes of this European Standard, the following terms and definitions apply. 3.1 operation identifiable activity for which a representative vibration magnitude measurement is made, being a combination of a type of work and a working condition EXAMPLE The type of work can be travelling for a lorry, lifting for a fork-lift truck, etc.; a working condition can be good or poor travelling surface, soft or hard material to excavate, etc. 3.2 work cycle operation or series of different operations, which is repeated SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 6 4 Quantities to be evaluated There are two principal quantities to be evaluated for each operation i during exposure to vibration: The frequency-weighted acceleration in metres per second squared (m/s2), expressed as the root-mean-square (r.m.s.) values awi for each of the three axes at the supporting surface; the total duration per day Ti of vibration exposure for operation i. The daily vibration exposure Al (8), in m/s2, for each direction l is defined as: ∑=iiwlillTaTkA201)8( (1) where awli
is the frequency-weighted r.m.s. value of the acceleration, determined over the time period Ti kx = ky = 1,4 for the x- and y-directions; kz = 1 for the z-direction l = x, y, z T0
is the reference duration of 8 h (28800 s) NOTE 1 The Physical Agents Directive 2002/44/EC allows an 8-h vibration dose value (VDV) instead of A(8). Where VDV is used, the Al(8) in this European Standard should be replaced by the daily vibration dose value in the l direction. The use of VDV instead of A(8) will generally result in a different evaluation of the health risk. NOTE 2 The values of kl in the x- and y-directions are based on sensitivity of seated persons but the same factors should be applied for other postures, e.g. standing. NOTE 3 If it can be shown that there is clearly a dominant direction it is sufficient to measure only this direction. The individual contribution of an operation or work cycle i to the daily vibration exposure can be calculated as: 0)8(TTakAiwlilli= (2) 5 Preparation of the measurement procedure 5.1 General The vibration exposure of an individual during a working day may involve a series of different operations, some of which may be repeated. The vibration exposure may vary greatly from one operation to another, e.g. due to the operator’s behaviour, the use of different machines or differences between the operations, or due to seasonal effects. Before making measurements, it is first necessary to identify the individual operations which are likely to contribute substantially to the overall exposure. The location and nature of each operation should be defined accurately and the total duration associated with the individual worker during the single day should be quantified. A survey should be undertaken to establish an “exposure profile”. This will help to determine the likely relative importance of each type of operation in the overall value of A(8), to identify those for which measurements are required, and to assist in the planning of any necessary exposure controls. The daily vibration exposure A(8) may be determined for a specific individual on a specific day. In some situations it may also be useful to calculate A(8) for a notional “typical” day’s exposure, using carefully selected representative vibration measurements and carefully considered exposure duration values. There is no method for evaluating the SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 7 combined vibration exposure for more than one day. Therefore, to know what is a typical day when vibration varies from one day to another, it is recommended to evaluate the variability of the daily vibration exposure A(8) over days. However, it is not acceptable to determine A(8) by averaging over several days on which different levels of variation exposure have occurred. Representative days of measurement shall be selected with care if evaluation concerns the individual risk. In particular, variation in exposure due to equipment used, work condition, or environments, shall be evaluated. 5.2 Exposure profile The exposure profile is used to identify those operations which contribute to the overall value of A(8) and to define the conditions under which measurements are to be made. It is important to make measurements for all the machines and operations which may give a significant contribution to the daily vibration exposure. For each operation identified, the following should be established: the machine being used; a full description of the operation (e.g. for a fork-lift truck: travelling or lifting or idling; for an excavator: digging or travelling; or a combination of these); operation conditions; nature of ground; state and tuning of the seat; the number of times the operation is performed per day; the average duration of the operation; if possible, the nature of the vibration (e.g. continuous, impulsive, shocks, principal direction, source). Identify all changes in the operating conditions where this might affect the vibration exposure.
EXAMPLE speed of mobile machines; a fork-lift truck may be travelling on a smooth surface inside a building, on an uneven surface inside (pits, thresholds, cables/hoses, debris, etc.) or on a rough surface outside; a dumper may be travelling unloaded or loaded; additional equipment which might affect vibration exposure, e.g. an agricultural tractor may be fitted with a slurry tanker or a plough. In addition, it may be useful to obtain: information from workers and supervisors on which operations they believe produce the highest vibration magnitude; estimates of the potential vibration hazards for each operation, using information from manufacturers on vibration emission values, or using published results of previous measurements on similar machines; manufacturers’ information on vibration magnitudes and the travelling conditions under which they have been measured; subject's posture, seat suspension topping or bottoming, use of backrest. In the case of short, well-defined exposures, different vibration magnitudes may be associated with each of the individual operations (e.g. loading and travelling over a rough surface with a wheel-loader, travelling and lifting with a fork-lift truck). In such cases, as many measurements as practicable should be performed for each individual SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 8 operation identified in the profile, and averaged as shown in equation (3). The daily duration of overall exposure to each operation should then be used to determine the overall exposure as shown in equation (1). For the case of long uninterrupted operations (e.g. driving a long-distance in a coach or lorry), two possible situations can exist. The first consists of essentially stationary vibration data, unchanging in its statistical characteristics; this might be true for a long journey at constant speed on a motorway. The measurement should be long enough to determine an accurate average vibration magnitude (see 5.4). The other possible situation consists of a continuous operation for which the vibration is not statistically stationary but changes with time. An approximate exposure profile can be obtained by grouping periods of substantially different vibration that are statistically stationary. Common examples of logical measurement groupings include grouping by road type (e.g. urban roads, country roads, motorways) or grouping by vehicle operation (e.g. travelling, other operations). As many measurements as possible should then be made for each operational grouping to provide a statistical description of the vibration. 5.3 Organization of the measurements Ideally, measurement of the daily exposure will be continuous throughout the working day and some modern instruments facilitate this. However, this is often impracticable and it is then necessary to establish a method of sampling appropriate periods of vibration exposure. The organization of the measurements will depend on the types of vibration exposure of the selected relevant operations. To evaluate the daily vibration exposure, two types of work pattern can be distinguished: a) The daily work consists of long uninterrupted operations (e.g. driving a long-distance in a coach or lorry). In this case, vibration measurements are made over a section of an operation or a complete operation, which may include short interruptions, which are valid parts of the normal operation (e.g. stops at traffic lights).
In addition to vibration magnitude information, the evaluation of daily vibration exposure requires a determination of the duration of exposure to vibration per day. b) The daily work consists of operations with different vibration magnitudes over short periods in respect to the daily working times (e.g. loading and travelling over a rough surface with a wheel-loader, travelling and lifting with a fork-lift truck). In such cases either the measurements are made separately for each of the different operations at the whole work and the results are combined or where the combination of operation duration is available the measurements are made directly for this combination. In addition to vibration magnitude information, the evaluation of daily vibration exposure requires a determination of the exposure duration associated with each operation. Separate measurements shall be made during those operations believed to cause the greatest vibration magnitudes in order to establish the highest short-term exposure. When identifying the important operations, it is important to consider events which occur outside the main work. For example, driving an agricultural tractor to and from the field may result in more vibration than the operation undertaken in the field. 5.4 Duration and number of vibration measurements The duration and number of measurements shall be selected so that a representative 8 h frequency-weighted vibration value can be established. Where continuous measurement throughout the day is not possible, the duration of measurements will be determined by the operation characteristics defined in 5.2. a) Where the daily work consists of long uninterrupted operations, a series of sample measurements, each of at least 3 min duration, should be taken at different times of the day, and averaged so that variations in vibration through the day are accounted for. The number, N, of sample measurements made shall be sufficient to show that the average value obtained is representative of the vibration occurring throughout the day. SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 9 The average vibration magnitude, in m/s2, of a series of N vibration magnitude samples is given by: ∑==NjjwjwtaTa121 (3) where wja is the measured vibration magnitude for samplej jt is the measurement duration of samplej
∑==NjjtT1 is the total measurement duration This procedure shall be carried out separately for vibration in each of the axes measured. b) Where the daily work consists of operations of shorter duration, which are repeated several times during a working day, measurements for determination of the 8 h energy-equivalent vibration value can be made over complete work cycles. The number of work cycles over which measurements are made shall be sufficient to show that the average value obtained is representative of the vibration from the operation throughout the day. c) Where no operations are repeated, the vibration from every operation shall be measured. d) Where there is no repeated work cycle of operations of short duration and the individual operations are shorter than 3 min, the operations can be repeated in order to collect measurements over a minimum of 3 min, see example in clause A.3. As an alternative, simulated operations may be organized for making measurements of 3 min duration. NOTE The requirement of a minimum of 3 min is due to statistical reasons. 5.5 Estimation of exposure time The total daily exposure duration shall be obtained for each operation or work cycle for which a vibration magnitude has been established. This may be based on; a) a measurement of the actual exposure duration of a single operation or work cycle; and b) information on the number of operations or work cycles per working day. The first of these will be a measurement to determine how long an operator is exposed to vibration, and from what source, during a specified period. Various techniques may be used, for example: use of a stopwatch; analysis of video recordings; activity sampling. A source of information may be work records, e.g. the number of lorries loaded and unloaded by fork-lift trucks. However, it is important to ensure that the information is compatible with the information required for an evaluation of daily vibration exposure. For example, work records might give very accurate information on the number of completed work items at the end of each day, but where there is more than one operator, or unfinished work items at the end of a shift, this information may not be directly applicable to a vibration exposure evaluation. NOTE Operators asked for information on their typical daily vibration exposure duration will normally give an estimate which includes periods of time when there is no vibration (e.g. idling, lifting for a fork-lift truck). Therefore, such an approach often results in an overestimation of the exposure duration. SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 10 6 Measurement of vibration
6.1 Measuring equipment 6.1.1 General Vibration measurement systems generally use accelerometers to detect the motion of the vibrating surface. Measurement systems shall be checked before and after measurements. Calibrated measurement systems shall be used. Vibration measurements may be made using simple single-unit vibration meters featuring built-in frequency weightings and integrating facilities. These systems are designed primarily to evaluate the vibration exposure at the workplace; they are generally sufficient for most situations covered by this European Standard. More sophisticated measurement systems are often based around some form of frequency analysis, (e.g. narrow band or one-third-octave bands); they may use digital or analogue data recorders to store time information. They may use computer-based data acquisition and analysis techniques. These systems are more costly and complex to operate than the single-unit systems. Frequency analysis will provide information on any dominant frequencies and harmonics which may help to identify effective vibration control measures. Where there is any doubt about the quality of the acceleration signal, it is useful to inspect the acceleration time history. Measuring and analysing equipment shall meet the requirements of !EN ISO 8041", which specifies minimum performance requirements (e.g. frequency weighting characteristics, tolerances, dynamic range, sensitivity, linearity and overload capacity) for appropriate measuring and analysing equipment.
!This" instrumentation can normally be used for evaluation of human exposure. 6.1.2 Accelerometers 6.1.2.1 General Accelerometers shall normally be used for measurement of vibration. In general, the choice of accelerometer will be defined by the expected vibration magnitude, the required frequency range, the physical characteristics of the surface being measured and the environment in which they are to be used. 6.1.2.2 Vibration magnitude The accelerometers chosen for the measurement shall be able to operate at the greatest acceleration magnitudes expected and have a suitable dynamic range to cope with smaller magnitudes at low frequencies. If the accelerometer responds at zero Hertz (e.g. piezoresistive accelerometers) the dynamic range shall be sufficient to accommodate both the gravitational component and the vibration. 6.1.2.3 Environmental conditions Accelerometer’s sensitivity to temperature, humidity and other environmental factors shall be considered (see !EN ISO 8041"). 6.1.3 Location and mounting of accelerometers 6.1.3.1 General Accelerometers shall be located so as to indicate the vibration at the interface between the human body and the source of vibration.
SIST EN 14253:2004+A1:2009
EN 14253:2003+A1:2007 (E) 11 Accelerometers oriented in different directions at a single measurement location shall be as close together as possible. The vibration shall be measured on the seat of seated persons and on the floor of standing persons. NOTE 1 On a mobile machine the measuring equipment should be secured with belts, straps, double-sided adhesive tape, etc. Some equipment such as recorders should be protected against shocks or transients. Different suspension systems may be used; a layer of soft foam placed between the secured equipment and the vibrating surface is generally sufficient. NOTE 2 If machines are operating on a slope, the accelerometers should be aligned with the operator's body rather than with the vertical and horizontal directions. Use of piezoelectric accelerometers or high-pass filtering is recommended to remove the DC component. 6.1.3.2 Seated persons The vibration shall be measured on the seat surface. For a non-rigid or resilient seat, the accelerometers shall be mounted in a semi-rigid disc as described in EN 30326-1.
NOTE There is no need to attach the disc on the seat since the fixing due to the operator mass is adequate in the range of frequencies being measured. Nevertheless the disc may be maintained in place by an adhesive tape. 6.1.3.3 Standing persons The vibration shall be measured on the surface on which the feet are most often supported. The accelerometers used for the measurement at the feet shall be rigidly fixed on the working platform. The vibration shall be measured on the supporting surface closely adjacent to the area of contact between the feet and that surface (usually within 100 mm of the centre of this area). If the working platform is covered by a resilient material, the accelerometers may be mounted in the middle of a rigid plate (about 300 mm x 400 mm) with the person standing on the plate. The mounted resonance shall be more than five times the maximum frequency of interest (see ISO 5348). Different mounting systems may be used to attach the accelerometer to the vibrating surface such as a powerful magnet (the force should be at least 1 kN), glue, double-sided thin adhesive tape, etc. 6.1.4 Frequency weighting Details on the parameters and tolerances for frequency weighting and band limiting are given in !EN ISO 8041" and ISO 2631-1.
Frequency weighting can be achieved by; analogue or digital filtering of the time signal; application of weighting factors to one-third-octave band or narrower-band frequency analysis spectra. It is important that digital methods, such as digital filtering and Fast Fourier Transform (FFT) analysis, are properly capable of providing accurate analysis over the full frequency range. The analyses should provide good resolution at low frequencies, and use a sample rate high enough to obtain accurate information at high frequencies. For most time signals, the Hanning window function is recommended for FFT analyses. NOTE If it has been established that the frequency range below 1 Hz is not relevant nor important, the range between the corner frequencies of the frequency weighting may be limited to 1 Hz to 80 Hz. 6.1.5 Use of data recorders Data recording can be achieved either using analogue or digital
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