SIST EN 13477-2:2011
(Main)Non destructive testing acoustic emission - Equipment Characterisation - Part 2: Verification of operating characteristic
Non destructive testing acoustic emission - Equipment Characterisation - Part 2: Verification of operating characteristic
This part of the standard specifies methods for routine verification of the performance of AE equipment comprising one or more sensing channels. It is intended for use by operators of the equipment under laboratory conditions. Verification of the measurement characteristics is recommended after purchase of equipment, modifications, use under extraordinary conditions, or if one suspects a malfunction. The procedures described in this European Standard do not exclude other qualified methods, e.g. verification in the frequency domain.
Zerstörungsfreie Prüfung - Schallemissionsprüfung - Gerätecharakterisierung - Teil 2: Überprüfung der Betriebskenngrößen
In diesem Teil der Norm werden Verfahren für die routinemäßige Prüfung der Funktion von AE-Messinstrumenten festgelegt, die mit einem Aufnehmerkanal oder mehreren Aufnehmerkanälen ausgestattet sind. Dieser Teil wurde für die Bediener der Messinstrumente für Prüfungen im Laboratorium konzipiert. Eine Überprüfung der Messcharakteristika wird empfohlen nach dem Kauf einer Ausrüstung, nach der Durchführung von Änderungen, nach einem Einsatz unter außergewöhnlichen Bedingungen oder wenn eine fehlerhafte Funktion zu befürchten ist. Die in dieser Norm beschriebenen Verfahren schließen andere qualifizierte Verfahren nicht aus.
Essais non destructifs, émission acoustique - Caractérisation de l’équipement - Partie 2: Vérifications des caractéristiques de fonctionnement
Cette partie de la présente norme spécifie des méthodes appliquées pour les vérifications de routine des performances d’un équipement d'émission acoustique comprenant une ou plusieurs voies de détection. Elle est destinée aux utilisateurs du matériel en conditions de laboratoire. La vérification des caractéristiques de mesure est recommandée après l'achat de l’équipement, après toute modification ou toute utilisation dans des conditions extraordinaires ou si l'on soupçonne un dysfonctionnement. Les modes opératoires décrits dans la présente norme n'excluent pas toute autre méthode qualifiée.
Neporušitveno preskušanje - Akustična emisija - Določevanje značilnosti opreme - 2. del: Preverjanje lastnosti delovanja
Ta del standarda določa metode za rutinsko preverjanje delovanja opreme AE, ki je sestavljena iz enega ali več senzorskih kanalov. Njegov namen je, da ga uporabljajo operaterji opreme pod laboratorijskimi pogoji. Preverjanje merilnih lastnosti se priporoča po nakupu opreme, spremembah, uporabi pod posebnimi pogoji ali če obstaja sum okvare. Postopki, opisani v tem evropskem standardu, ne izključujejo drugih kvalificiranih metod, npr. preverjanja v frekvenčni domeni.
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Zerstörungsfreie Prüfung - Schallemissionsprüfung - Gerätecharakterisierung - Teil 2: Überprüfung der BetriebskenngrößenEssais non destructifs, émission acoustique - Caractérisation de l’équipement - Partie 2: Vérifications des caractéristiques de fonctionnementNon destructive testing acoustic emission - Equipment Characterisation - Part 2: Verification of operating characteristic19.100Neporušitveno preskušanjeNon-destructive testingICS:Ta slovenski standard je istoveten z:EN 13477-2:2010SIST EN 13477-2:2011en,fr,de01-februar-2011SIST EN 13477-2:2011SLOVENSKI
STANDARDSIST EN 13477-2:20011DGRPHãþD
SIST EN 13477-2:2011
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 13477-2
September 2010 ICS 19.100 Supersedes EN 13477-2:2001English Version
Non-destructive testing - Acoustic emission - Equipment characterisation - Part 2: Verification of operating characteristic Essais non destructifs, émission acoustique - Caractérisation de l'équipement - Partie 2: Vérifications des caractéristiques de fonctionnement
Zerstörungsfreie Prüfung - Schallemissionsprüfung - Gerätecharakterisierung - Teil 2: Überprüfung der Betriebskenngrößen This European Standard was approved by CEN on 30 July 2010.
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, Croatia, 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:
Avenue Marnix 17,
B-1000 Brussels © 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 13477-2:2010: ESIST EN 13477-2:2011
EN 13477-2:2010 (E) 2 Contents Page Foreword .41 Scope .52 Normative references .53 Terms and definitions .54 Required test equipment .54.1 List of required equipment .54.2 Test signal waveforms .64.2.1 Continuous sine wave .64.2.2 Triangular modulated sine wave .64.2.3 Sine²-modulated sine wave .74.2.4 Rectangular modulated sine wave .84.2.5 Pulse .94.2.6 Repetitive signals .94.3 Test Body . 104.4 Shielding test plate . 105 Sensor verification. 105.1 General . 105.2 Uses . 105.3 Procedure . 105.3.1 Preliminary examination . 105.3.2 Sensitivity verification . 105.3.3 Verification of electrical shielding . 115.3.4 Electrical noise verification of a sensor-preamplifier combination . 116 Preamplifier verification . 126.1 General . 126.2 Verification of DC-current consumption . 126.3 Measurement of preamplifier characteristics . 136.3.1 General . 136.3.2 Gain . 136.3.3 Bandwidth . 136.3.4 Electronic noise . 156.3.5 Dynamic range . 166.3.6 Pulsing test . 167 AE signal processor verification . 167.1 Overview . 167.2 Bandwidth
and filter roll-off verification . 177.3 Detection threshold verification . 177.4 AE signal processor noise verification . 177.5 Burst signal parameter verification . 187.5.1 General . 187.5.2 Peak amplitude . 187.5.3 Duration . 207.5.4 Rise time . 207.5.5 Ring down count . 207.5.6 Energy . 207.6 Parameters for continuous signal . 218 External parameter verification . 219 System acquisition rate verification . 21SIST EN 13477-2:2011
EN 13477-2:2010 (E) 3 10
∆∆∆∆t measurement verification . 2211 Documentation . 22Annex A (informative)
Sensor performance check form . 25Annex B (informative)
Preamplifier performance check form . 27Annex C (informative)
AE signal processor - bandwidth & noise verification form (one per channel) . 29 SIST EN 13477-2:2011
EN 13477-2:2010 (E) 4 Foreword This document (EN 13477-2:2010) has been prepared by Technical Committee CEN/TC 138 “Non-destructive testing”, the secretariat of which is held by AFNOR. 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 March 2011, and conflicting national standards shall be withdrawn at the latest by March 2011. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 13477-2:2001. EN 13477 consists of the following parts under the general title Non-destructive testing — Acoustic emission — Equipment characterisation: Part 1: Equipment description; Part 2: Verification of operating characteristic. 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, Croatia, 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 13477-2:2011
EN 13477-2:2010 (E) 5 1 Scope This part of the standard specifies methods for routine verification of the performance of AE equipment comprising one or more sensing channels. It is intended for use by operators of the equipment under laboratory conditions. Verification of the measurement characteristics is recommended after purchase of equipment, modifications, use under extraordinary conditions, or if one suspects a malfunction. The procedures described in this European Standard do not exclude other qualified methods, e.g. verification in the frequency domain. 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 1330-1:1998, Non destructive testing — Terminology — Part 1: List of general terms EN 1330-2:1998, Non destructive testing — Terminology — Part 2: Terms common to the non-destructive testing methods EN 1330-9:2009, Non-destructive testing — Terminology — Part 9: Terms used in acoustic emission testing EN 13477-1:2001, Non-destructive testing — Acoustic emission — Equipment characterisation — Part 1: Equipment description IEC 60050 (all parts), International Electrotechnical Vocabulary 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 1330-1:1998, EN 1330-2:1998, EN 1330-9:2009 and IEC 60050 (all parts) and the following apply. 3.1 AE signal processor part of an AE channel for the conversion of the output of the preamplifier to digital signal parameters NOTE The AE signal processor may include additional support functions, e.g. preamplifier power supply, test pulse control, transient recorder, and more. 3.2 arbitrary function generator (AFG) electronic device for generating a programmable test signal (burst) 3.3 DC calibrator electronic device for generating an adjustable or programmable DC voltage of appropriate accuracy for stimulating an external parametric input 4 Required test equipment 4.1 List of required equipment The following minimum test equipment is required: SIST EN 13477-2:2011
EN 13477-2:2010 (E) 6 a) test body; b) shielding test plate; c) Hsu-Nielsen source, for sensor sensitivity verification; d) sweep function/variable pulse generator (if function not included in f)); e) multimeter, e.g. for DC voltage and DC current measurement; f) test signal generator, e.g. AE calibrator or arbitrary function generator (AFG); g) variable attenuator, graduated in decibels, can be part of the test signal generator; h) DC-calibrator, for external parameter stimulation; i) DC-power-supply, for preamplifier supply, with a proper circuit to decouple and terminate the AE signal, if the power is fed-in over the signal wire; j) RMS voltmeter, with known or settable time constant or time window; k) dual channel storage oscilloscope, for preamplifier verification, peak noise measurement and identification of any artefacts on the AE signal. NOTE Items i) to k) can be substituted by a verified AE signal processor comprising peak amplitude and RMS measurement. The inaccuracy of the test signal generator shall be significantly lower than the acceptable inaccuracies given in this standard and summarized in Table 3. Less accurate test signal generators can be used, if the inaccuracy of each pattern is measured and considered during verification. The reproducibility of the DC calibrator output shall be significantly lower than the acceptable inaccuracy of the external parameter verification. The inaccuracy of the DC calibrator at the used measurement levels shall be obtained and considered during verification (see Clause 8). All electric/electronic test items shall be calibrated to ensure traceability to SI units. 4.2 Test signal waveforms The following types of test signals shall be used to verify the operating characteristics of the AE measurement system: 4.2.1 Continuous sine wave This type of test signal shall be used to verify the frequency response and gain of the preamplifier and the continuous signal level accuracy of the AE signal processor. 4.2.2 Triangular modulated sine wave This type of wave simulates an AE burst signal, see Figure 1. It is defined by the following characteristics: A = amplitude; R = rise-time; D = duration; f = carrier frequency. SIST EN 13477-2:2011
EN 13477-2:2010 (E) 7
Key [mV] amplitude Figure 1 — Triangular modulated sine wave in time (left) and frequency (right) domain The measured rise time may be shorter than the visible rise time of the test signal because rise time measurement starts at the time of the first threshold crossing. Table 1 shows the dependency of this threshold crossing delay on the difference between maximum amplitude and threshold setting in an AE channel. 4.2.3 Sine²-modulated sine wave A sine²-modulated signal (see Figure 2) can be used as an alternative to a triangular modulated sine wave. Due to its smooth begin, peak and end, its spectrum is very pure and the influence of filter overshoot and filter ring down behaviour is reduced. This signal can be used to obtain the frequency response of the bandpass of a preamplifier or AE signal processor by burst peak amplitude measurement.
Key [mV] amplitude Figure 2 — Sine²-modulated sine wave in time (left) and frequency domain (right) NOTE The shown signal corresponds to the following function: ))/(²(sin)/2sin(][SWpBSpSWNSpSWNUNUP××××××=ππ (1) 0=N to )SWpB(SpSW×, in integer steps (2) where N = number of each sample in time order; SpSW = Samples per sine wave (48 in Figure 2); SWpB = Sine waves per burst (41 in Figure 2); U[N] = Voltage of sample N; SIST EN 13477-2:2011
EN 13477-2:2010 (E) 8 PU = Peak amplitude (100 mV in Figure 2) of simulated burst. The resulting carrier frequency fc is a function of the sample time interval (ts): ()SpSWtf×=sc1 (3) or the time interval (ts) for a certain carrier frequency is
()SpSWft×=cs1 (4) Example in Figure 2: ts = 1/(200 kHz x 48) = 104.167 ns Similar to the triangular modulated sine wave, the rise time measured by an AE signal processor is shorter than the visible rise time of the test signal, because rise time measurement starts at the time of the first threshold crossing. This so-called “first threshold crossing delay” depends on the difference of maximum amplitude and detection threshold in dB and is listed for the two modulated test signals in Table 1. Table 1 First threshold crossing delay versus amplitude to threshold ratio
for a sin2 and triangular modulated test signal Threshold Sin² modulated first threshold crossing delay % of signal rise time Triangular modulated
first threshold crossing delay % of signal rise time A – 20 dB 19,7 11,0 A – 25 dB 15,0 6,0 A – 30 dB 12,3 3,5 A – 35 dB 8,3 3,0 A – 40 dB 7,6 1,0
4.2.4 Rectangular modulated sine wave This type of signal is defined by the characteristics A, D and f, see
4.2.2 and Figure 3.
Key [mV] amplitude Figure 3 — Rectangular modulated sine wave in time (left) and frequency domain (right) SIST EN 13477-2:2011
EN 13477-2:2010 (E) 9 4.2.5 Pulse This test signal shall be used to check the measurement of ∆t. It is defined by the characteristics A (amplitude) and D (pulse duration). Figure 4 shows the output of an arbitrary function generator where one sample in a cyclic output buffer was set to 0,8 V, all others to zero. The buffer was output at a sample interval of 50 ns. A pulse duration between 50 ns and 500 ns is recommended. The pulse amplitude shall cause a signal amplitude of about 6 dB above the detection threshold. A much higher amplitude may cause additional threshold crossings by ring down cycles as shown in Figure 5.
Figure 4 — Pulse 4.2.6 Repetitive signals This signal is used to verify the signal processing rate. It is a series of pulses as described in 4.2.5. It is defined by A (amplitude), D (pulse duration) and f (repetition frequency), typically 1 Hz – 10 kHz. Figure 5 shows an example with 1/f = 160 µs, taken after the band pass filter of an AE signal processor. The maximum reasonable repetition frequency is limited by the ring down effect of the band pass filter, if a pulse causes multiple threshold crossings.
Key [mV] amplitude Figure 5 — A series of transient signals (pulses) 160 µs apart behind the band pass SIST EN 13477-2:2011
EN 13477-2:2010 (E) 10 4.3 Test Body This can take different forms, e.g. a metallic block, or a plate, or an acrylic rod. Once chosen, the dimensions, construction material, Hsu-Nielsen source position, sensor mounting position and usage shall be controlled to ensure reproducibility of results. The surface in contact with the sensor shall be flat and smooth. The test body shall be isolated acoustically from the work bench to avoid interference from external noise sources. 4.4 Shielding test plate This is a small flat metallic plate sufficient in size to cover the sensor’s sensitive area. The plate shall be connected to a sine wave; therefore, it shall be electrically isolated from earth. Once chosen, the dimension of the plate and the thickness of the non-conductive layer, if applicable, shall be controlled. The test plate shall be given an identifier for use in the verification report. See Figure 6 for the setup. 5 Sensor verification 5.1 General The following procedure allows rapid comparison of the sensitivity of sensors. The deterioration of the sensors can result from e.g. mechanical shock, exposure to high temperature, high ionizing radiation or a corrosive environment, water ingress, a damaged connector or cable. 5.2 Uses The specific objectives of the procedure for checking sensors are: warning of degrading response or damaged internal shielding; determining when a sensor is no longer suitable for use; checking sensors that are known to have been exposed to high-risk conditions; creating matched sets of sensors to achieve uniform performance; verifying sensors quickly and reliably and assisting trouble shooting, when a channel shows a fault. 5.3 Procedure 5.3.1 Preliminary examination Allow the test body, sensors and couplant to adopt the ambient temperature. Perform a preliminary examination of the sensor to identify any obvious mechanical damage, paying particular attention to connector and cable, if any. 5.3.2 Sensitivity verification For the sensitivity verification of a sensor, a verified AE signal processor shall be used. If the sensor does not comprise a preamplifier, a verified reference preamplifier and sensor cable of specified length shall be used. The frequency filters in the preamplifier and AE signal processor shall properly cover the bandwidth of the sensor. SIST EN 13477-2:2011
EN 13477-2:2010 (E) 11 Mount the sensor on the test body using an appropriate couplant. Be sparing with the couplant, e.g. approximately 0,1 cm3 of silicone grease is adequate for most types of sensors. Press the sensor firmly down onto the test body to insure a good coupling. Take care the sensor and attachment cannot move during the test. The use of a constant force device is recommended. Using the Hsu-Nielsen source, make a minimum of 3 lead breaks at the prescribed position on the test body. In each case, record the signal amplitude in units of dBAE, on the test record. The difference between lowest and highest reading shall be within 3 dB. Before proceeding to the next sensor, remove the couplant from the verified sensor. The test temperature, lead diameter and hardness, and bandwidth of preamplifier and AE signal processor shall be recorded. 5.3.3 Verification of electrical shielding In case of an internal defect of the electrical shielding, the sensor signal can be overlaid by electrical noise from the test object which is difficult to differentiate from acoustical noise. This verification step shall observe such a defect. Mount the sensor on the shielding test plate in acoustically quiet environment. If the contact surface of the sensor is electro-conductive, use a thin non-conductive layer of specified thickness, e.g. a self adhesive foil. Connect the test plate to a sine wave using a shielded cable as shown in Figure 6. Connect the cable shield to earth. For each sensor model the sensor manufacturer shall specify the test voltage US1PP (usually 10 V), the test frequency fS (usually 2,5 times the sensor’s main resonance frequency) and the acceptable maximum for the sensor output voltage before preamplification US2PP (usually 2 mV). Manufacturer specification and measured values shall be reported (see Annex A).
Figure 6 — Shielding verification set-up 5.3.4 Electrical noise verification of a sensor-preamplifier combination The electrical noise level of a sensor and preamplifier combination shall be measured in acoustically quiet environment with the sensor dismounted from a structure. The measurement set-up is according to 6.3.4. The noise level is measured in specified units and shall not exceed the noise specification of the manufacturer. The measured value shall be reported on the test record (see Annex A). SIST EN 13477-2:2011
EN 13477-2:2010 (E) 12 6 Preamplifier verification 6.1 General Annex B shows an example for a preamplifier verification report that includes the manufacturer’s acceptance limits and results of measurements. Perform a preliminary examination of the preamplifier to identify any obvious mechanical damage, paying particular attention to connectors and cables, if any. The following procedure applies to voltage preamplifiers. 6.2 Verification of DC-current consumption Figure 7 shows the test set-up for the verification of the DC current consumption. The following applies to a preamplifier with 28V DC supply fed-in over the signal wire. For preamplifiers with other power requirements, the setup shall be properly adapted. Connect the 28 V DC power supply as shown in Figure 7 to the preamplifier output over a DC current meter and a 50 Ohm resistor in parallel with a 10 mH inductor.
With no input from the sine wave generator measure and record the stand by current,ISB
in mA.
Use a sine wave of a frequency within the pass band of the preamplifier and set the preamplifier AC output to full scale. Measure and record the full scale current IFS
in mA. Standby current ISB and full scale current IFS shall not exceed the manufacturer’s specifications.
Figure 7 — Set-up for measurement of DC current consumption SIST EN 13477-2:2011
EN 13477-2:2010 (E) 13 6.3 Measurement of preamplifier characteristics 6.3.1 General For the following measurements, the preamplifier power supply shall be at the prescribed voltage. Good measurement practice requires: correct impedance matching throughout the measurement chain; avoidance of ground loops; avoidance of electromagnetic interference. 6.3.2 Gain The gain factor is the ratio of the output (UOUT) to the input voltage (UIN) of an amplifier at the geometric mean frequency (see 6.3.3). It is converted to dB by the following formula: ()INOUT10log20GainUU×= (5) Figure 8 shows the recommended set-up. The output of the test signal generator is connected over an attenuator to the input of the preamplifier under verification. A proper termination resistor shall be connected in parallel to the high impedance preamplifier input. The attenuation is to be set to the same dB value as the nominal gain. The test signal shall be set to 50 % of the preamplifier’s output range and to the mean frequency of its bandwidth. At correct gain, both channels of the oscilloscope shall show equal amplitudes. For the verification of the preamplifier function with a burst type AE signal, a sine²-modulated sine wave shall be used. Alternatively, for the verification of the preamplifier function with a continuous AE signal, a continuous sine wave shall be used.
Figure 8 — Test set-up for the verification of preamplifier gain and bandwidth 6.3.3 Bandwidth Figure 8 shows the test set-up for the verification of preamplifier bandwidth and gain. The bandwidth shall be obtained from the -3 dB points on the frequency response curve, compared to their geometric mean frequency. The -3dB points are also called “cut-off” frequencies “FLO“ and “FHI“. The geometric mean frequency is calculated as follows:
SIST EN 13477-2:2011
EN 13477-2:2010 (E) 14 ()2/1HILOMFFF×= (6) where FM geometric mean of FLO and FHI; FLO nominal lower cut-off frequency, hereafter called FHP (for high-pass);
FHI nominal upper cut-off frequency, hereafter called FLP (for low-pass). See Figure 9, an example where both roll-offs are 48 dB/octave.
Key [dB] RMS [kHz] frequency Figure 9 Characteristics of a bandpass filter with 48 dB/octave roll-off for the lower and upper cut-off frequencies The test signal amplitude shall be set to 50 % of the preamplifier’s output range at the geometric mean frequency FM. This output voltage refers to 0 dB in the frequency response curve. The corner frequency FHP shall be obtained at the lower -3 dB frequency point (95 kHz in Figure 9). FLP shall be obtained at the upper -3 dB frequency point (850 kHz in Figure 9). “HP roll-off” means the signal level reduction in dB/octave of the high-pass, to be obtained at 0,5 x FHP (-48 dB at 47,5 kHz in Figure 9). “LP roll-off” means the signal level reduction in dB at twice of FLP. Accordingly, LP roll-off shall be obtained at 2xFLP (-48 dB at 1,7 MHz in Figure 9). The verification results FHP, HP roll-off, and FLP, LP roll-off shall be reported (see Annex B) and checked for compliance with the acceptance limits. SIST EN 13477-2:2011
EN 13477-2:2010 (E) 15 6.3.4 Electronic noise For the reproducibility of the noise measurement the following items shall be specified and reported in the test record: input termination of the
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