EN 13860-1:2003
(Main)Non destructive testing - Eddy current examination - Equipment characteristics and verification - Part 1: Instrument characteristics and verification
Non destructive testing - Eddy current examination - Equipment characteristics and verification - Part 1: Instrument characteristics and verification
The purpose of this standard is to identify the functional characteristics of a general purpose eddy current equipment and to provide methods for their measurement and verification. The evaluation of these characteristics will permit a well defined description and comparability of an eddy current equipment. By careful choice of the characteristics, a consistent and effective eddy current examination system can be designed for a specific application. Where accessories are used, these should be characterised using the principles of this standard. This standard does not give acceptance criteria for the characteristics.
Zerstörungsfreie Prüfung - Wirbelstromprüfung - Kenngrößen von Prüfeinrichtungen und deren Verifizierung - Teil 1: Kenngrößen von Prüfgeräten und deren Verifizierung
Diese Europäische Norm erläutert Funktionskennwerte von Wirbelstromprüfeinrichtungen für die allgemeine Anwendung und zeigt Verfahren für deren Messung und Verifizierung. Die Bewertung dieser Kennwerte erlaubt eine verständliche Beschreibung und Vergleichbarkeit von Wirbelstromprüfeinrichtungen. Mit einer sorgfältigen Auswahl der Kennwerte ist es möglich, ein angemessenes und effizientes Wirbelstromprüfsystem für einen besonderen Anwendungsfall aufzubauen. Zusatzeinrichtungen sollten, sofern sie eingesetzt werden, nach den Grundsätzen der vorliegenden Norm beurteilt werden.
Essais non destructifs - Examen par courants de Foucault - Caractéristiques et vérification de l'appareillage - Partie 1: Caractéristiques de l'appareil et vérifications
La présente Norme européenne identifie les caractéristiques fonctionnelles d'un appareillage à courants de Foucault à usage général et fournit des méthodes pour les mesurer et les vérifier.
L'évaluation de ces caractéristiques permet de donner une description bien définie de l'appareillage à courants de Foucault et d'assurer la comparabilité entre appareils.
Un système d'examen par courants de Foucault, cohérent et efficace, peut être conçu en procédant à un choix scrupuleux des caractéristiques pour une application spécifique.
Lorsque des accessoires sont mis en �uvre, il convient de les caractériser en appliquant les principes de la présente norme.
La présente Norme européenne ne donne ni l'étendue de la vérification ni les critères d'acceptation des caractéristiques. Celles-ci sont définies dans les documents d'application.
Neporušitveno preskušanje – Preiskave z vrtinčnimi tokovi – Karakteristike naprav in njihovo overjanje – 1. del: Karakteristike aparatur in njihovo overjanje
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Zerstörungsfreie Prüfung - Wirbelstromprüfung - Kenngrößen von Prüfeinrichtungen und deren Verifizierung - Teil 1: Kenngrößen von Prüfgeräten und deren VerifizierungEssais non destructifs - Examen par courants de Foucault - Caractéristiques et vérification de l'appareillage - Partie 1: Caractéristiques de l'appareil et vérificationsNon destructive testing - Eddy current examination - Equipment characteristics and verification - Part 1: Instrument characteristics and verification19.100Neporušitveno preskušanjeNon-destructive testingICS:Ta slovenski standard je istoveten z:EN 13860-1:2003SIST EN 13860-1:2004en01-marec-2004SIST EN 13860-1:2004SLOVENSKI
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SIST EN 13860-1:2004
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13860-1February 2003ICS 19.100English versionNon destructive testing - Eddy current examination - Equipmentcharacteristics and verification - Part 1: Instrumentcharacteristics and verificationEssais non destructifs - Examen par courants de Foucault -Caractéristiques des équipements et vérification - Partie 1:Caractéristiques des appareils et vérificationZerstörungsfreie Prüfung - Wirbelstromprüfung -Kenngrößen von Prüfeinrichtungen und deren Verifizierung- Teil 1: Kenngrößen von Prüfgeräten und derenVerifizierungThis European Standard was approved by CEN on 12 December 2002.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the 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 translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and UnitedKingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2003 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13860-1:2003 ESIST EN 13860-1:2004
EN 13860-1:2003 (E)2ContentspageForeword.31Scope.42Normative references.43Terms and definitions.44Eddy current instrument characteristics.44.1General characteristics.44.2Electrical characteristics.55Verification.105.1General.105.2Levels of verification.105.3Verification procedure.115.4Corrective actions.116Measurement of the electrical characteristics of the instrument.126.1Measuring requirements.126.2Generator unit.126.3Input stage characteristics.156.4Signal processing.176.5Output.266.6Digitisation.26Annex A (informative)
Principle of frequency beat method.27Annex B (informative)
Method of measurement of the linearity range between an output O and an inputI.29Annex C (normative)
Alternative measurement of the input impedance.31SIST EN 13860-1:2004
EN 13860-1:2003 (E)3ForewordThis document (EN 13860-1:2003) has been prepared by CEN/TC 138, "Non-destructive testing", the secretariat ofwhich is held by AFNOR.This European Standard shall be given the status of a national standard, either by publication of an identical text orby endorsement, at the latest by August 2003, and conflicting national standards shall be withdrawn at the latest byAugust 2003.EN 13860 comprises a series of European Standards for Eddy current examination - Equipment which is made upof the following:EN 13860-1Non-destructive testing - Eddy current examination - Equipment characteristics and verification -Part 1: Instrument characteristics and verification.EN 13860-2Non-destructive testing - Eddy current examination - Equipment characteristics and verification -Part 2: Probe characteristics and verification.prEN 13860-3Non-destructive testing - Eddy current examination - Equipment characteristics and verification -Part 3: System characteristics and verification.Annexes A and B are informative, annex C is normative.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,Slovakia, Spain, Sweden, Switzerland and the United Kingdom.SIST EN 13860-1:2004
EN 13860-1:2003 (E)41 ScopeThis European Standard identifies the functional characteristics of a general purpose eddy current equipment andprovides methods for their measurement and verification.The evaluation of these characteristics permits a well defined description and comparability of an eddy currentequipment.By careful choice of the characteristics, a consistent and effective eddy current examination system can bedesigned for a specific application.Where accessories are used, these should be characterised using the principles of this standard.This European Standard gives neither the extent of verification nor acceptance criteria for the characteristics. Theyare given in the application documents.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text, and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this EuropeanStandard only when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred to applies (including amendments).EN 1330-5:1998Non-destructive testing - Terminology - Part 5: Terms used in Eddy current testing.EN 12084Non-destructive testing - Eddy current testing - General principles and guidelines.3 Terms and definitionsFor the purposes of this European Standard the terms and definitions given in EN 1330-5:1998 apply.4 Eddy current instrument characteristics4.1 General characteristics4.1.1 Type of instrumenta) An instrument is of general purpose application when the relationship between the measured quantity and thedisplay or output is established by the user. A range of probes can be connected to the instrument. Theinstrument manufacturer shall provide details of the internal electrical characteristics in order that the user candesign the examination system. The examination system shall be in accordance with EN 12084. The user shallbe able to vary the value of frequency, gain, balance (unless automatic balance), phase, filters, and gain andzero of the display.b) An instrument is of specific application when the relationship between the measured quantity and the displayor output is explicitly defined in the range of application. The probe is specific to the instrument. For this type ofinstrument, this standard may be partially applied.4.1.2 Power supplyThe instrument can be powered by batteries or by the local A.C. power supply. The nominal values of voltage,frequency, and power consumption shall be stated together with the tolerance for correct operation.SIST EN 13860-1:2004
EN 13860-1:2003 (E)54.1.3 SafetyThe instrument and its accessories shall meet the applicable safety regulations, e.g. electrical hazard, surfacetemperature, explosion, etc.4.1.4 TechnologyThe instrument can be wholly analogue or part analogue and part digital.The excitation can be single frequency, multifrequency, swept frequency, or pulsed.The instrument can be single or multichannel.The instrument settings can be manual, remote controlled, stored, or pre-set.The instrument shall have component outputs and can be with or without a self contained display.4.1.5 Physical presentationThe instrument can be portable, cased, or rack mounted, with the component parts integrated or modular.The weight and size shall be specified for the instrument and its accessories.The plugs and sockets shall be specified regarding type and pin interconnections.The instrument model number and the serial number shall be clearly readable and located in a readily accessibleplace.4.1.6 Environmental effectsThe warm up time necessary for the instrument to reach stable operating conditions within specified limits shall bestated.The temperature, humidity, and vibration ranges for normal use, storage and transport shall be specified for theinstrument and its accessories.The instrument shall conform to relevant electromagnetic compatibility (EMC) regulations.4.2 Electrical characteristics4.2.1 GeneralThe electrical characteristics of an instrument shall be evaluated after the warm up time has elapsed.The electrical characteristics are only valid for the stated operating conditions.When relevant, the stability of the specified values with time, for specified environmental conditions, shall be stated.The electrical characteristics apply to various items of the functional block diagram of the instrument. Whereapplicable, they are provided by the manufacturer. Some of these characteristics can be verified according to themethodology described in clause 6.4.2.2 Functional block diagramThe functional block diagram of a typical general purpose eddy current instrument is shown in Figure 1.SIST EN 13860-1:2004
EN 13860-1:2003 (E)6Figure 1 — Functional block diagram of an eddy current instrument4.2.3 Generator unitThe source of excitation is the generator unit.In the case of alternating excitation (sinusoidal, triangular, rectangular, etc.) the characteristics to be defined are:¾ type of generator: current or voltage;¾ type of excitation: single or multifrequency;¾ frequency setting: range, step size, deviation from nominal value;¾ harmonic distortion;¾ amplitude setting: range, step size, deviation from nominal value, maximum output voltage or current;¾ source impedance with frequency dependence.In the case of multifrequency excitation it shall be stated if frequencies are injected simultaneously or multiplexed,independent or related, and the multiplexing sequence, when relevant.4.2.4 Input stage characteristicsThe input stage interfaces the probe to the instrument. It provides impedance matching and amplification asrequired.The characteristics to be defined are:¾ input impedance with frequency dependence;¾ gain setting range, step size, deviation from nominal value;BalanceGene-ratorProbeInputHF signal& demod.LF-signalDisplayAccessoriesDigitisationXYSIST EN 13860-1:2004
EN 13860-1:2003 (E)7¾ maximum input voltage;¾ common mode operating parameters, when relevant.4.2.5 BalanceBalance is the compensation of the signal to achieve a predetermined operating point, e.g. zero. The compensationmay be performed manually or automatically, at the input stage, or during HF signal processing, or duringdemodulated signal processing, or on the display.The characteristics to be defined are:¾ maximum input range, which can be compensated;¾ residual value at balance (expressed as a percentage of a specified range, e.g. full scale output).4.2.6 High frequency signal processing4.2.6.1 HF filteringFilters reduce the signal frequency content which can have an undesirable effect on the test result.The filters used before demodulation are referred to as carrier frequency filters (HF filters). These are usually bandpass filters which suppress any signal frequencies which do not correspond to the excitation frequency.The characteristics to be defined are:¾ gain;¾ bandwidth at 3dB attenuation;¾ rate of attenuation;¾ transient response.4.2.6.2 HF amplificationThe characteristics to be defined are:¾ gain setting range, step size, deviation from nominal value;¾ input signal range;¾ bandwidth;¾ output saturation level.4.2.6.3 DemodulationSynchronous demodulation extracts the vector components from the HF signal.For positive polarity of demodulation a delay in the signal will cause the signal vector to rotate clockwise. Thepolarity of demodulation shall be positive and shall be confirmed.The characteristics to be defined are:¾ wave shape of the reference signal, e.g. sine, square, pulse;¾ bandwidth for each wave shape of reference signal;SIST EN 13860-1:2004
EN 13860-1:2003 (E)8¾ phase dependent amplitude deviations;¾ phase dependent phase deviations.Amplitude demodulation extracts the low frequency amplitude variations from the HF signal.4.2.7 Demodulated signal processing4.2.7.1 Vector amplificationVector amplification generally consists of two transmission channels of identical design. These channels amplifythe vector components produced by synchronous demodulation. In some instruments, these components can beamplified with different gains.The characteristics to be defined are:¾ gain setting range, step size, deviation from nominal value;¾ input signal ranges;¾ bandwidth;¾ output saturation level.4.2.7.2 LF filteringThe filters used after demodulation are referred to as low frequency filters (LF filters). The bandwidth of the filter ischosen to suit the application, e.g. wobble, surface speed, etc.The characteristics to be defined are:¾ gain;¾ bandwidth at 3 dB attenuation;¾ rate of attenuation;¾ transient response.4.2.7.3 Phase settingPhase setting permits rotation of the demodulated signal vector on the complex plane display.The characteristics to be defined are:¾ range;¾ step size;¾ amplitude variation of the signal vector with phase setting;¾ deviation of indicated phase rotation from actual phase rotation.4.2.8 Output and signal displayThe type of display can be an indicator display, or a hard copy display, or a screen display.The type of presentation can be e.g. complex plane, ellipse, time synchronous, frequency spectrum, imaging.SIST EN 13860-1:2004
EN 13860-1:2003 (E)9The related characteristics to be defined include:¾ size;¾ graticule divisions - major and minor;¾ full scale display voltage range or time range;¾ transfer factor e.g. volts/division;¾ linearity;¾ bandwidth.The output can be analogue, digitised, or logical.The characteristics of analogue outputs to be defined are:¾ voltage or current range;¾ output impedance;¾ linearity;¾ bandwidth.The characteristics of digitised outputs to be defined are:¾ data protocol;¾ serial or parallel;¾ voltage and current levels;¾ speed and format;¾ sampling rate;¾ A/D resolution, range and linearity.The characteristics of logical outputs to be defined are:¾ voltage and current levels;¾ settling delay;¾ hysteresis;¾ active high or low.4.2.9 Digitisation4.2.9.1 GeneralWhenever digitisation is performed the following characteristics shall be defined:¾ stage of digitisation in the signal processing;¾ digitisation technique;SIST EN 13860-1:2004
EN 13860-1:2003 (E)10¾ A/D resolution;¾ sampling rate.The information supplied by the manufacturer shall therefore include data on the following parameters.4.2.9.2 Stage of digitisationDigitisation may be performed either before or after signal demodulation.4.2.9.3 Digitisation techniqueDigitisation can be performed using an internal clock or an external encoder.4.2.9.4 A/D ResolutionResolution is the nominal value of the converter input voltage corresponding to one digitisation bit.The number of digitisation bits is an equally useful information even though it can be directly accessed through themaximum input voltage and the resolution.4.2.9.5 Sampling rateThe sampling rate is the frequency, in hertz, at which the A/D conversion is made.5 Verification5.1 GeneralFor a consistent and effective eddy current examination it is necessary to verify that the performance of thecomponent parts of the eddy current test system is maintained within acceptable limits.The physical condition of the reference blocks shall be verified to be within acceptable limits before being used toverify the system, or probes.The measuring equipment used for verification shall be in a known state of calibration.For a better understanding, the verification procedure is identically described in all three parts of EN 13860.5.2 Levels of verificationThere are three levels of verification. Each level defines the time intervals between verification and the complexityof the verification.It is understood that initial type testing has already been done by the manufacturer or under his control.LEVEL 1:Global functional checkA verification performed at regular intervals of time on the eddy current test system using reference blocks to verifythat the performance is within specified limits.The verification is usually performed at the examination location.The time interval and the reference pieces are defined in the verification procedure.LEVEL 2:Detailed functional checkA verification on an extended time scale, performed to ensure the stability of selected characteristics of the eddycurrent instrument, probe, accessories, and reference blocks.SIST EN 13860-1:2004
EN 13860-1:2003 (E)11LEVEL 3:CharacterisationA verification performed on the eddy current instrument, probe accessories, and reference blocks to ensureconformity with the characteristics supplied by the manufacturer.The organisation requiring the verification shall specify the characteristics to be verified.The main features of verification are shown in Table 1.Table 1 — Verification levelsLEVELOBJECTTYPICAL TIMEPERIODINSTRUMENTSRESPONSIBLEENTITY1Global functioncheckStability of systemperformance.Frequently.e.g hourly, dailyReference blocks.USER2Detailed functionalcheck andcalibrationStability of selectedcharacteristics of theinstrument, probesand accessories.Less frequently butat least annually andafter repair.Calibratedmeasuringinstruments,reference blocks.USER3CharacterisationAll characteristics ofthe instrument,probes andaccessories.Once(on release)and when required.Calibrated laboratorymeasuringinstruments andreference blocks.MANUFACTURER,USER5.3 Verification procedureThe characteristics to be verified are dependant on the application. The essential characteristics and the level ofverification shall be specified in a verification procedure.The examination procedure for the application shall refer to the verification procedure. This can restrict the numberof characteristics to be verified for a defined application.Sufficient data on the characteristics featured in an instrument, probe, and reference piece, shall be provided inorder that verification can be performed within the scope of this standard.5.4 Corrective actionsLEVEL 1:When the performance is not within the specified limits, then a decision shall be made concerning theproduct examined since the previous successful verification. Corrective actions shall be made to bring theperformance within the acceptable limits.LEVEL 2:When the deviation of the characteristic is greater than the acceptable limits specified by themanufacturer or in the application document, then a decision shall be made concerning the instrument, the probeor the accessory being verified.LEVEL 3:When the characteristic is out of the acceptable range specified by the manufacturer or by theapplication document, then a decision shall be made concerning the instrument, the probe or the accessory beingverified.SIST EN 13860-1:2004
EN 13860-1:2003 (E)126 Measurement of the electrical characteristics of the instrument6.1 Measuring requirementsAll measurements described in the following chapters are made at the inputs and outputs of the instrument. Thesemeasurements do not require opening the instrument, (black box concept).Keeping the black box concept, any alternative method, the equivalence of which shall be demonstrated,may be used.Shielded, non-inductive resistors shall be used as loads. The resistors shall have a value of 50 ohm. Additionalmeasurements may be made with other values of resistor. However it needs to be stressed that the characteristicsof an instrument can be significantly altered if a different load is necessary for the instrument or the application. Insuch a case the load used shall be noted in the test report.The measurements described hereafter shall be made at three values in each decade of the frequency range e.g.the factor 1, 2 and 5.It should be noted that the filter settings used for a specific application will modify characteristics, e.g. bandwidth,gain setting accuracy and phase setting accuracy. In this case the measurement conditions for verification shall bespecified in the application document.6.2 Generator unit6.2.1 Excitation frequency6.2.1.1 Definition and measurement conditionsThe frequency shall be measured at the generator output of the instrument loaded in accordance with 6.1.The percentage deviation from the displayed value is:100valuedisplayedvaluemeasuredvaluedisplayed´-The maximum modulus of deviation in the total range of frequencies measured shall be reported.6.2.1.2 Measurement methodThe frequency may be measured using the beat frequency method, a frequency meter, or a spectrum analyser.In the case of multifrequency, multiplexed instruments then appropriate instrumentation shall be used, e.g.spectrum analyser.6.2.2 Harmonic distortion6.2.2.1 Definition and measurement conditionsFor a generator producing a sinusoidal waveform the harmonic content is used as a measure of the deviation froma pure sinusoid.The harmonic distortion is described by the distortion factor, k:k = quantity galternatin the of value RMSharmonics of valueRMS,UUkå=/2nSIST EN 13860-1:2004
EN 13860-1:2003 (E)13An approximate value is given by:UUUk212-=whereU RMS value of the alternating quantity;U1RMS value of the first harmonic (fundamental);UnRMS value of the nth harmonic.The distortion factor shall be measured at the generator output of the instrument loaded in accordance with 6.1.In the case of multifrequency instruments then sufficient instrumentation shall be used, e.g. spectrum analyser.The value to be stated is the maximum distortion factor for each frequency.6.2.2.2 Measurement methodThe distortion factor may be measured using a distortion factor bridge, a spectrum analyser, or a high pass filter.6.2.3 Source impedance6.2.3.1 Definition and measurement conditionsThe source impedance Zs is the internal impedance of the generator unit, see Figures 2a and 2b, measured ateach independent output.Key1 = ZsFigure 2a — Voltage driven generatorSIST EN 13860-1:2004
EN 13860-1:2003 (E)141)Current driven generator2)Equivalent voltage driven generatorKey1 = ZsFigure 2b — Current driven generatorFigure 2 — Internal impedance of the generator unit6.2.3.2 Measurement methodThe method proposed is based on the assumption that the complex source impedance Zs can be considered asresistive.The generator output is loaded with a resistor R1 (normally 50 W). The voltage V1 is measured with an appropriatevoltmeter. It is important to verify that the measured value is less than the maximum output voltage.Repeat the measurement with a resistor R2 ( normally R2 = 0,5 R1) and measure V2.The source impedance Zs, expressed in ohms, is:112221sRVRVVVZ--=NOTE 1Verify that the values of V1, V2 and the intensities V1/R1, V2/R2 are less than the maximum output voltage andcurrent.NOTE 2The choice of R1 and R2 determines the precision of the measured value of Zs.6.2.4 Maximum output voltage V0max6.2.4.1 Definition and measurement conditionsThe maximum output voltage is the peak-to-peak voltage at the generator terminals with no load applied and thegenerator set to give its maximum output.6.2.4.2 Measurement methodThe maximum output voltage is measured using an oscilloscope or an adequate voltmeter. The measuringinstrument shall have a high input impedance (> 1MW) and a bandwidth compatible with the frequency range of theeddy current instrument. Typically the maximum usable frequency of the measuring instrument shall be at leasttwice the maximum frequency of the eddy current instrument.SIST EN 13860-1:2004
EN 13860-1:2003 (E)15The measured values can be presented in graphical format.6.2.5 Maximum output current IOmax6.2.5.1 Definition and measurement conditionsThe maximum output current is the peak value of the current measured at the generator terminals when terminatedwith the lowest permissible resistive load as defined by the manufacturer. The generator is set to give its maximumoutput.6.2.5.2 Measurement methodThe maximum output current is measured with a current probe connected to an oscilloscope or with an ammeter.The measuring instrument shall have a low impedance (typically less than 10% of the smallest resistive load), anda bandwidth compatible with the frequency range of the eddy current instrument.The measured values can be presented in graphical format.6.3 Input stage characteristics6.3.1 Maximum allowable input voltage6.3.1.1 Definition and measurement conditionsThe maximum allowable input voltage is related to safety, saturation, and non-linearity.It is respectively the peak input voltage at minimum gain, corresponding to:a) the maximum value given by the manufacturer. This is the safe input voltage such that the instrument is notdamaged; it includes common mode operating limits when relevant;b) 90 % of the output at saturation;c) the non-linearity exceeding a given value. The maximum allowable deviation from linearity shall be defined inthe application document.In all cases the input voltage applied shall not exceed that given in a).6.3.1.2 Measurement method6.3.1.2.1 Related to saturationThe frequency beat method is used (see principle in annex A). The input voltage is to be provided by a sine wavegenerator. The difference between the frequency of the signal generator and the selected frequency of theinstrument shall not be greater than 10% of the stated bandwidth of the instrument.The gain of the instrument is set to minimum and the filters set to have minimum effect. The input and each outputis loaded with a pure resistor.Ensure that the instrument is balanced. The input signal is measured using a high impedance voltmeter.The output signal is displayed on an oscilloscope and its X and Y components are measured using a peakvoltmeter.The input voltage is increased from zero to the safe input voltage given by the manufacturer, and the positive andnegative peak values of each component of the output voltage are plotted (Vx+, Vx-,Vy+, Vy-). The first value of thefour variables (i.e. that corresponding to the smallest value of the input) which ceases to increase when reaching aSIST EN 13860-1:2004
EN 13860-1:2003 (E)16steady value Vs, provides the saturation output level Vs. The input value thus obtained is then decreased until thecomponent being monitored reaches an output value of 90 % Vs.The input voltage obtained corresponds to the maximum allowable input voltage, related to saturation, (seeFigure 3).Key1Output voltage2Input voltageNOTEThe relative amplitudes of each output are for example only.Figure 3 — Measurement of the
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