Dynamic measurement activities at PTB Hans-Jürgen von Martens Physikalisch-Technische Bundesanstalt (PTB), Germany

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1 Metrology Club, Meeting at NMIJ in Tsukuba July 7 Dynamic measurement activities at PTB Hans-Jürgen von Martens Physikalisch-Technische Bundesanstalt (PTB, Germany. General considerations on dynamic measurements and calibrations Simultaneously Simultaneously measured measured pressure pressure curves curves s s and and their their difference difference (Drop-ball (Drop-ballapparatus apparatus Pressure p(t Reference Reference Calibrated Calibrated Pressure difference Pressure difference. Survey PTB activities for pressure, mass, mass flow, force, torque.3 %. % 3. Techniques, standards and traceability for motion quantities (vibration and shock. Applications (vibration and shock 5. Summary and conclusions Dynamic characterization a - Generalized dynamic measurement system Mass m(t PTB Working Group.3 Dynamic Weighing (Dipl.-Ing. Karsten Schulz z i (E - influence quantities from environment, e.g. temperature, humidity Dynamic characterization a : Complex sensitivity for measurand x ˆ j( ϕ y ϕ x' S x = S x e Exampe Automatic rail-weighbridges (OIML R6: Type SOLAR, Pfister Waagen GmbH Germany with modulus y Sˆ x = x ˆˆ and phase shift Δϕx = ( ϕ ϕ y x z i (G - influence quantities from generator e.g. distortion, hum, noise z i (G: evaluated with transfer function to be calibrated Magnitude and phase shift complex sensitivity a (linear are usually measured by defined sinusoidal or shock excitation. xˆ amplitude x ϕ x initial phase x ŷ amplitude y ϕ y initial phase y Loadcell forces 5 PTB Working Group.33 Dynamic pressure measurement (Dipl.-Ing. Ernst Franke PTB Working Group.5 Hydrodynamic Test Field (Dr. Rainer Engel Pressure p(t Computer controlled calibration pressure impulse apparatus PTB Standard straingauge manometers for 69 MPa 3 MPa MPa Mass flow m& (t Examples Flowmeters to be calibrated UUT: Small arms, shooting tools, alarm wapons, handheld powder actuated tools 3 6

2 Force F(t Periodic PTB Working Group.3 Periodical Forces (Dr. Rolf Kumme Facilities for periodical forces have been developed to determine deviations from static calibrations (dynamic properties force s Examples Examples static static and and dynamic dynamic calibrations calibrations force force s s Static calibration PTB Working Groups. Realization Torque/.3 Impact Dynamics in cooperation (Dr. Th. Bruns Torque T(t Sinusoidal torque - principle generation, measurement and calibration Angular acceleration ϕ&(t & Moment inertia θ Air bearing Optical radial grating Dynamic calibration Transducer signal A(t T ( t = θ & ϕ ( t Torque Rotational exciter Most critical: Screw connections 7 Force F(t Periodic Facility for 7 kn PTB Working Group.3 Realization Acceleration (Dr. Th. Bruns - after retirement Dr. H.-J. von Martens Arrangement for the dynamic calibration force s Light reflector Interferometer Velocity v(t Displacement s(t Rotational angle Φ(t Angular velocity Ω(t Angular acceleration α(t Accelerometer Loading mass F(t = m a(t Force Air bearing Measuring signal Measuring signal exciter 8 Force F(t Impact PTB Working Group.3 Impact Dynamics (Dr. Thomas Bruns In terms metrology, and shock are represented by six motion quantities: Rotational angle Φ(t Velocity v(t Angular velocity Ω(t Applications impact force calibrations Facility Facility for for generation generation and and measurement measurement force force impacts impacts Force: H.-J. von kn Martens, Dynamic Impact measurement period: activities ms at PTB Velocity: 3 m/s Air bearings both masses Laser 9 Motion Dependence on time Direction Quantity General Sinusoidal Translational (i.e. linear Rotational (i.e. circular Displacement s(t Angular acceleration α(t Displacement s s (t s( t = sˆ cos( ω t + ϕ s ds v( t = vˆ cos( ωt + ϕv, Velocity v v( t = dt π vˆ = ωsˆ, ϕv = ϕs + Acceleration a d s a ( t = a( t = aˆ cos( ωt + ϕa, dt aˆ = ω sˆ, ϕa = ϕs + π Rotation angle Φ Φ (t Φ ( t = Φˆ cos( ωt + ϕφ dφ Angular velocity Ω Ω ( t = Ω( t = Ωˆ cos( ωt + ϕ Ω, dt ˆ π Ω = ωφˆ, ϕ Ω = ϕφ + Angular acceleration α d Φ α ( t = α( t = ˆ α cos( ωt + ϕα, Metrology Club, Meeting at NMIJ dtsukuba t July 7 ˆ α = ω Φ, ˆ ϕ = + π α ϕφ

3 Example Example dynamic dynamic behaviour behaviour a : : Transfer Transfer function function a piezoelectric piezoelectric accelerometer, accelerometer, description descriptionvariant variant Schematic accelerometer (compression type mass piezoelectric disks (spring ( = S f Sref f + f Qf Vectorial representation sensitivities Complex sensitivity S(f as function frequency f S ref f Q reference sensitivity (undamped resonance frequency quality factor (simplified description as nd order system Normalized magnitude S /S ref Normalized phase shift ϕ/(-π Q = 3... Normalized frequency f /f Q = 3 Modulus Phase shift... Normalized frequency f /f Primary Calibration Methods for the calibration vibration and shock s - ISO 663 series documentary standards (state July 7 Velocity v(t Displacement s(t reciprocity Shock Angular vibration Secondary Calibration Angular ISO 663- Calibration Basic concepts comparison Shock comparison vibration comparison Cal. in severe environment * Transverse sensitivity ** Resonance testing 537-* ** Rotational angle Φ(t renumbered after revision (if any Angular acceleration α(t Angular velocity Ω(t Other calibration methods 663- Calibration laser vibrometers 663- Calibration seismometers 663- XX Calibration force s 3 Implemented at PTB: Interferometry H.-J. von Martens, Dynamic (663-, Footnotes: Zero stage project, measurement -3, -5 activities at PTB Comparison (663-, -, -3 Committee Draft 6 Transfer function accelerometers, description variant ** Expression as 9-parameter model a ln( * spec. in IEEE 5. f hp ref S ( f = S b( T T ref ref f f f Qf hp lp f S ref reference sensitivity f lp low-pass cut-f frequency b temperature coefficient f (undamped resonance frequency T temperature f ref reference frequency T ref reference temperature Q Quality factor f frequency a amplitude slope/decade f hp high-pass cut-f frequency ISO 663-:, rectilinear ISO 663-3: Shock acceleration ISO 663-5:, angular Primary calibration: NMI (PTB Laser National calibration service (DKD Secondary and lower-order calibration: Comparison with reference Manufacturer calibration laboratory (e.g. Polytec ISO 663-:, rectilinear ISO 663-: Shock acceleration ISO 663-3:, angular Traceability chain established in Germany PTB - Accredited calibration laboratories (DKD - Non-accredited calibration laboratories Measurement equipment used in production processes (e.g. car manufacturer Metrology Club, Meeting at NMIJ Tsukuba July * So far, 7 one cal. lab. ( DKD-K-78 is H.-J. von Martens, Dynamic measurement activities at accredited PTB for Laser, too. 7 * Transfer function accelerometers, description variant 3: 3: Table measurement results for forselected frequencies.9 Universal method and technique PTB for generating and measuring rectilinear and angular motion quantities (vibration and shock Mach-Zehnder heterodyne interferometer with frequency conversion and digital data processing Charge sensitivity in pc/(m/s² Frequency in Hz Fringe counting method (PTB MF standard device Sine-approximation method (PTB HF standard device Observation from independent measurement methods and techniques: Systematic deviations from behaviour nd order system. Conclusion: Variant 3 reflects most accurately the accelerometer behaviour (metrological approach. Methods, techniques and procedures are used at PTB in compliance with ISO 63-, ISO 663-3, ISO and ISO CD

4 Low-frequency acceleration standard. Hz to Hz (national measurement standard High-frequency acceleration standard Hz to khz (national measurement standard Velocity v(t Displacement s(t Laser interferometer Velocity v(t Displacement s(t isolation system II Laser interferometer system Air-borne vibration exciter Acceleration: m/s² Air-borne vibration exciter (stroke m Displacement: nm to mm Acceleration: m/s² Displacement: m isolation system I 9 Low-frequency acceleration standard Hz to 63 Hz (national measurement standard Shock acceleration standard 5 m/s² to 5 km/s² (national measurement standard Laser interferometer Velocity v(t Shock exciter with air-bearings hammer and anvil Displacement s(t Air-borne vibration exciter Laser interferometer isolation block II isolation block I isolation block II Acceleration: 5 m/s² Displacement:.6 m isolation block I Shock duration 8 ms to.8 ms 3 Medium-frequency acceleration standard Hz to 5 khz (national measurement standard Shock acceleration standard km/s² to km/s² (national measurement standard Velocity v(t Shock acceleration exciter using shock wave propagation in bars m in length Displacement s(t Accelerometer to be calibrated Laser interferometer Air-borne vibration exciter Pneumatic shock generation using pairs steel balls as mitigators Acceleration: m/s² Displacement: mm Active vibration isolation system Shock duration: µs to 3 µs Laser interferometer mounted on a vibration isolation system

5 Angular acceleration standard.3 Hz to khz (national measurement standard Demonstration the need for dynamic calibrations (example angular accelerometer: Relative sensitivity changes up to 8 % at frequencies between and 5 Hz Angular acceleration α(t Angular velocity Ω(t Rotational angle Φ(t 3. Frequency response (modulus sensitivity a servo angular accelerometer (Type ASMP-, Schaevitz Angular acceleration : rad/s² Rotational angle: rad Diffraction grating laser interferometer Air-borne angular acceleration exciter Active vibration isolation system Voltage Sensitvity in mv/(rad/s² Metrology Club, Meeting at NMIJ Tsukuba July 7 H.-J. von Martens, Dynamic Frequency measurement in Hz activities at PTB 8 Velocity v(t Displacement s(t Simultaneous motion generation (X, Y, Z: user-defined (sine, shock, random etc. Measurement by laser Temperature chamber: - C to 5 C Multi-component acceleration standard Hz to khz (bandwidth Peak acceleration: m/s² Displacement (peak to peak: 5 mm Payload: kg Laser interferometer mounted on an active vibration isolation system Amplitude linearity a back-to-back reference accelerometer A statistical procedure a linear approximation with calculation the upper and lower P = 95 %- confidence limits is an efficient tool for trend checks: The slope the approximation line can lie within the confidence limits. Charge sensitivity in pc/(m/s² ,% measurement results linear approximation 95% upper and lower confidence limit Acceleration amplitude in m/s² linearity test The accelerometer behaves amplitude- linear within the experimental uncertainty Air-suspended (6 t, active vibration isolation 6 9 Rotational exciter multi-component acceleration standard Linearity test an accelerometer standard, using sinusoidal and shock excitation (frequency spectrum Frequency range (bandwidth:, Hz to,8 khz Angular acceleration amplitude: rad/s² Angular velocity (rotating state : ± 8 rad/s Payload: 7,5 kg Sensitivity in pc/(m/s² % Shock excitation (spectral component 6. khz Sinusoidal excitation at 6. khz and m/s² Linear approximation 95 % upper and lower confidence limit 6 8 Acceleration peak value in km/s² Amplitude-linearity test over 3 decades Within the wide peak amplitude range, no systematic deviation are observable (experimental uncertainty ±.5 %. Note: Similar results were obtained for other spectral frequencies 7 3 5

6 Long-term stability a single-ended reference accelerometer measured at 6 Hz Charge sensitivity in pc/(m/s² ,% measurement results linear approximation 95% upper and lower confidence limit Time in days Long-term stability test The slope the stright line can be changed within the confidence limits, even up to a positive slope. Hence, no systematic long-term drift occurs which would exceed the experimental uncertainty.5 %. Charge Ladungsübertragungskoeffizient sensitivity in pc/(m/s² Influence lading mass on sensitivity a back-to-back accelerometer model 7 (manufacturer Endevco Massebelastung auf 7 auf Bouche-Erreger (rechts/links gem. Investigation at PTB using high-frequency vibration exciter,38 y = E-x - 5E-7x +,65,37 y = 7E-x - E-7x +,56,36,35 y = 3E-x - E-7x +,55,3 y = E-x - E-7x +,55,33,3,3,3,9,8,7,6,5,,3, Frequency Frequenz in Hz Masse g Masse g Masse g Masse 6g berecnedt 9,6 khz Polynomisch (Masse g Polynomisch (Masse g Polynomisch (Masse g Polynomisch (Masse 6g Note, however, that long-term drifts in the order some -3 are typical for piezoelectric accelerometers. 3 3 Primary calibration a back-to-back (BB accelerometer standard using dummy masses to simulate actual loading conditions A BB accelerometer is designed to mount any to be calibrated on the top surface, to apply the comparison calibration method in compliance with ISO Modulus and phase shift the complex sensitivity the BB accelerometer standard depend on the mass mounted on its top surface. To simulate the loading conditions when later used in a calibration laboratory, appropriate dummy masses are mounted on the BB accelerometer when the latter is calibrated (preferably in an NMI. ISO 663- Primary vibration calibration by laser examples a set dummy masses u ( ti arctan and phase unwrapping u ( ti Shock sensitivity (time domain Interferometer signal processing in shock measurements (PTB Time domain sd ( ti st ( vd ( i ti Low-pass filtering Sensitivity for spectral frequencies f n the shock spectrum upeak S Sh = apeak S n = uˆ( aˆ( Low-pass filtering Frequency domain vt ( i DFT jπf Differentiation Differentiation vˆ n = vˆ( ϕ v, n = ϕv ( aˆ n = aˆ( ϕ a, n = ϕa( Low-pass filtering IDFT upeak S Sh = apeak S n = a*(t i uˆ( aˆ( at ( i 3 35 Dissemination the unit acceleration (example: sinusoidal linear acceleration Accelerometer standard calibrated by laser Measured with shock acceleration standard km/s².7 mv.6 m/s².5. % Dynamic behaviour an accelerometer in the time domain (S sh and frequency domain (S n time domain S sh upeak S Sh = apeak frequency domains n S n = uˆ( aˆ( Ssh Sensitivity.3.. Sn(6 khz Calibration a single-ended (SE accelerometer by comparison to the back-to-back (BB accelerometer standard. Sn( khz.9.8 Sn( khz.7 km Measured with shock acceleration s² 55 standard 5 km/s² Acceleration peak value

7 Mounting effects - rotation test: Deviations vibration amplitudes measured in mounting positions 5, 35, 5 and 35 the accelerometer, from the mean value for all positions Deviations vibration amplitudes sensed simultaneously by two laser light spots shifted by 8 about the axis the vibration exciter.5 position 5 position 35 position 5 position 35 6 Relative deviation in % Relative deviation in % Positions the laser light spot Frequency in Hz Frequency in Hz Position to 8 Position 9 to 7 Position + 8 to Even if mounting conditions ISO 538 are observed, residual mounting effects may influence the measurement uncertainty 37 Vibrating part without disturbing motion Example: moving part PTB HF exciter, khz Vibrating part with inhomogeneous amplitude distribution (membrane effect Example: one the exchangeable moving parts the PTB MF exciter Upper postion moving part Lower postion moving part 38 Vibrating part with tilting and transverse motion Example: moving part PTB HF exciter, khz Example disturbing effects inhomogeneous vibration distribution CIPM Key comparison CCAUV.V-K, single-ended (SE accelerometer standard Transverse vibration amplitude in % Normalized transverse vibration amplitude 6 Measured by 3D-laser vibrometer Measured simultaneously by digital laser vibrometer 5 3 Frequency in khz Transverse motion indicated by 3D vibrometer and Digital laser vibrometer (manufacturer Polytec GmbH Amplitude distribution over the moving part Tilting motion indicated by Scanning vibrometer (manufacturer Polytec GmbH deviation D i in %.5. Example 7 Accelerometer state6 the art BB-accelerometer ArmatureSE-accelerometer.3 5. Base. reference Relative deviations D i PTB results from Reference Values Key Comparison CCAUV.V-.K ( Frequency in Hz frequency in Hz Relative deviation D i* in % 39 7

8 Comparison accelerometer shock calibrations in Germany Results accredited cal. laboratories and PTB results Shock-shaped acceleration - Measurement capabilities PTB.9 pc/(m/s².85 Reference value +% calibration laboratories: secondary shock calibration (Comparison method, ISO 663- Lab., method A A Shock pendulum Lab., method D Lab. 3, method A B Linear shock calibrator VW Lab. 3, method B (air bearing Shock sensitivity accelerometers Magnitude and phase shift accelerometers at spectral frequencies (shock excitation.8 Lab., method A Lab., method C PTB Reference value C Pneumatic shock calibrator D Drop ball calibrator Sensitivity S qa Reference value -%.6 m/s² Acceleration peak value â PTB: primary shock calibration (ISO Outcome: All deviations from ref. value were < % Demonstration compliance with accredited measurement uncertainty % Specified is expanded uncertainty for coverage factor k = (coverage probability P = 95 %. 3 6 CIPM Key Comparison CCAUV.V-K Participants NMIs from 5 RMOs Pilot Laboratory: PTB (Hans von Martens Quantities angular acceleration, angular velocity and rotational angle (sinusoidal. Measurement capabilities PTB Phase Amplitudes shift angular angular accelerometers, acceleration, angular angular velocity velocity s, and rotational rotational angle angle Sensitivities (modulus s angular accelerometers, and laser vibrometers angular velocity s, rotational angle s and laser vibrometers H.-J. von Martens, C. Elster, A.Link, A. Täubner, W. Wabinski FINAL REPORT ON KEY COMPARISON CCAUV.V-K PTB Braunschweig, October, Accelerometer % BB accelerometer, frequency: 6 Hz Relative deviation D i * from KCRV and expanded uncertainty (k =, U i * Armature (x i-x Ref/x Ref x - Top reference Specified is expanded uncertainty for coverage factor k = (coverage probability P = 95 %. - PTB BNM- Metrology CSIRO- Club, CMI Meeting CSIR- at NMIJ CENAM Tsukuba NRC July KRISS 7NMIJ VNIIM NIST NMi- H.-J. CESTA von Martens, NML Dynamic measurement NML activities at PTB VSL 7 Quantity acceleration (sinusoidal. Measurement capabilities PTB Acceleration Phase amplitude Sensitivity shift accelerometers and (modulus sensitivity and accelerometers (modulus laser vibrometers laser vibrometers 3 m/s² â max Summary and conclusions For mechanical quantities, dynamic measurement techniques applied at PTB were demonstrated. For 6 motion quantities (vibration and shock the advanced state PTB was presented in detail meas. standards developed at PTB represent the state the art in vibration & shock measurements. Acceleration amplitude a U rel =. â min ISO Methods and a traceability chain have been developed and implemented in Germany and worldwide. The meas. capabilities are used to identfy the dynamic behaviour meas. s and instruments. In vibration and shock measurements, various effects are to be considered in uncertainty evaluations. -5. Hz Frequency Specified is expanded uncertainty for coverage factor k = (coverage probability P = 95 %. PTB continues to extend the metrological foundation dynamic measurements in cooperation with advanced national metrology institutes such as NMIJ. For further information, see or contact hans-juergen.v.martens@ptb.de 5 8 8