the current state of – calibration facilities and...

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Dr. Th. Bruns “Acceleration” & “Impact Dynamics”

The Current State of Vibration Metrology

in Germany

Dr. Thomas BrunsHead of the Working Groups

“Acceleration” and “Impact Dynamics”of the

Physikalisch-Technische Bundesanstalt

March 2006

Invited Visit to NMIJ / AIST (Tsukuba/Japan)


Contents of the presentation

• Introduction of the Working Group “Acceleration”– Calibration Facilities and Methods– Current research Topics (general)– Special Interest “Laser Vibrometer Calibration”

• Metrology Infrastructure in Germany (DKD)– The German Calibration Service– Accreditation procedures– How to handle “primary methods”

• Fundamental research in Dynamics– Dynamic Force Measurement/calibration– Dynamic Torque Measurement/calibration


Introduction

The Working Group 1.31“Acceleration”

of the PTB


Airborne Armature max. Displacement: 1 m

Low Frequency (0,1 Hz to 20 Hz)


Low Frequency (0,4 Hz to 63 Hz)


Medium Frequency (10 Hz to 5 kHz)

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High Frequency (10 Hz to 20 kHz)


High Frequency (10 Hz to 20 kHz)

49Section Acceleration


Angular Acceleration (0,4 Hz to 1 kHz)


Hammer-Anvil Principle

Air-borne anvilAir-borne hammer

Spring unit

Low Intensity Shock (50 m/s² to 5000 m/s²)


High Intensity Shock (1 km/s² to 100 km/s²)(durations 100 µs to 300 µs)


Multicomponent facility (x-y-z-φ)

3


Survey of Applied Methods

• Measurement of Transducer output– DVM for Magnitude of sensitivity over frequency– Transientrecorder for Magnitude & Phase, Shock

• Measurement of acceleration (interferometer)1. Fringe counting of homodyne Michelson Interferometer2. Homodyne Quadratur (modified Michelson) Interferometer3. Heterodyne (~3 MHz fm) time-interval analysis4. Heterodyne (~3 MHz fm) digital quadrature5. Heterodyne (~20 MHz fm) digital quadrature

2-4 with Sine-Approximation Method5 with numerical differentiation

• Traceability of frequency to PTB-CS1/CS2 (10 MHz) standard


Current research Interest

Shock calibration of accelerometers:

• Practical Equivalence of Shock- and Sine-calibration

• Parametric identification/description of accelerometers

• Goal is a better Definition of the shock sensitivity


Current Research Interests

• Shock Calibration, the Symptoms:


• Shock Calibration the Reason:

shpeak

peak

aS

u=

Interferometricacceleration

Sensorvoltage


Current Research Interests

• Shock Calibration, Maybe Solution:


Current Research Interest

• Extending the usability range of homodyne interferometry

• Laser Vibrometer Calibration in Magnitude and Phase

• New Exciter Technologies

– minimizing disturbing motions

– maximizing amplitude and frequency

• Multi-component excitation for

– Multi-component calibration (sensitivity matrix)

– transverse sensitivity under load

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Special Interest Laser Vibrometer Calibration



PTB’s Set-Up for Laser Vibrometer Calibration


100 1000 10000

-0 ,25

-0 ,20

-0 ,15

-0 ,10

-0 ,05

0,00

0,05

0,10

0,15

0,20

0,25

0,30

rel.

Abw

eich

ung

in %

F requenz in H z

R eferenz-V ibrom eter M odell 1 (C S 18P S P E K T R A ) R eferenz-V ibrom eter M odell 2 (C S 18P C hina)



Example of heterodyne signal processing in a laser-interferometer standard(extract from the WD of 16063-41)



Special Requirements for Laser Interferometer Standards

• Laser spot size between 0,1 mm and 0,5 mm

• Amplitude stabilized photo detector signal

• digital demodulation technique

• stabile delay time for phase measurements

• external trigger option

(extract from the WD of 16063-41)


TheMetrology Infrastructure

of Germany


Metrology Infrastructure

Metrology and testing in Germany is characterized by

• a metrology system promoted and supported by the State

• a decentralized, federal system which takes thestructure of the German federal states into account

• a separation of the metrology and test sector into areasunder legal control and industrial metrology.

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The metrology infrastructure is embedded in:• International Framework given by CIPM/BIPM RMO etc.

• Definition of units, fundamental constants, terms and procedures

• coordination of international intercomparissons

• The Mutual Recognition Arrangement• mutual acceptance of measurement result (calibration certificates,

test reports) under accepted conditions

=> reduction of barriers in global trade

• Rules and regulations of international written standardsISO 9000, ISO 17025, ISO 16063

• International regulations for Accreditation EA / ILAC



NMI

(PTB)

NationalCalibr. Service

(DKD)

ManufacturerCalibration Laboratory

Measurement Equipmentused in Production Processes

National primary standards, based on laser interferometry

Secondary calibration, based onreference / transfer standards

Working standards, home-madecalibration procedures

Traceable calibration required



NMI

(PTB)

NationalCalibration Service

(DKD)

ManufacturerCalibration Laboratory

Measurement Equipmentused in Production Processes

covered by international and national written standards

• ISO/IEC 17025:2005• ISO 16063• DKD-R 3-1 part 1 to 4• validated methods

defined in the manufacturers internal Quality ManagementSystem

BIPM



Accreditation of Calibration Labs in Germany:• Accreditation Body is part of the DKD (deutscher Kalibrierdienst)

Member of EA (Europe) and ILAC (worldwide)

task of accreditation and supervision of the Labs

• Supervision in two levels:Every 18 months a regular surveillance visit (technical on site audit) concerning one of the measurands

- check of changes in the technical premises of the calibration

- random inspection of parts of the QM-System

- typically a comparison calibration against a national standard

Every 60 month a complete surveillance audit

- on site audit concerning all measurands and the whole QM-System

- same complexity as the original accreditation audit

• The accreditation proves the competence of the calibration lab and the traceability of the performed calibrations to the SI-System of Units.



Accreditation of Calibration Labs in Germany:• Laboratory applies for the accreditation and submits the

documentation of its QM-System

• Auditors check the documentation off site with respect to formal aspects (auditors from accreditation body)technical aspects (specialist in the field, typical PTB scientific staff)

• On site assesment with both auditors in the calibration labrealization of the formal aspects of the QM-System (reports, standards, archives, customer relations, staff education,etc.) correct implementation, execution of the calibration procedures,monitoring of environmental conditions, uncertainty contributions,…



0100200300400500600700800900

10001100

1982 1986 1990 1994 1998 2002

AccreditationsExtensions

A m

o u

n t

Accreditations+ 100 %

1056

372

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DKD-CalibrationLaboratories in Germany


Primary Methods

Example: DKD-Accreditation of the calibration laboratory of the manufacturerSPEKTRA SCHWINGUNGSTECHNIK UND AKUSTIK GmbH DresdenDKD-K 27801 for primary calibration of Laser Vibrometers

Primary calibration system CS 18P HF


Primary Methods

Traceability to the SI units may be achieved by reference to an appropriate primary standard or by reference to a natural constant, the value of which in terms of the relevant SI units is known and recommended by the CGPM and the CIPM

Calibration laboratories that maintain their own primary standard or representation of SI units based on fundamental physical constants can claim traceability to the SI system only after this standards have been compared directly or indirectly, with other similar standards of an NMI

Comparisons are in every aspect the most reliable way to get widely accepted measurements


Primary Methods

The case of SPEKTRA:

• SPEKTRA’s CS18P uses primary Methods

• SPEKTRA is accredited for prim. cal. of– Accelerometers

– Laser Vibrometers

– etc …

• SPEKTRA does not maintain it’s own primary standard

• SPEKTRA as DKD-Lab is traceable to PTB


Some Fundamental Research

in Dynamicsof the PTB


Dynamic Force (Impact)

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SAE J211: Surface Vehicle Recommended PracticeInstrumentation for Impact Test – part 1 – Electronic Instrumentation

“…Accuracy of reference equipment for calibration:…Forces and displacements:

(No method for the evaluation of the dynamic response during calibration of data channels for forces and displacements is included since no satisfactory method is known at present.) “

Dynamic Force (Impact)(applicable standards)


ISO 6487: Road Vehicles Measurement Techniques in Impact Tests - Instrumentation -

“…Accuracy of reference equipment for calibration: …Forces and displacements:

No method for the evaluation of the dynamic response during calibration of data channels for forces and displacements is included in this international standard since no satisfactory method is known at present. The problem will be reconsidered later.”

Dynamic Force (Impact)(applicable standards)



F(t) = m · a(t)


Fmax = 20 kN

m1 = 10,112606 (15) kgm2 = 9,881528 (15) kg






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Diffraction grating

Accelerationmechanism

Laser-Doppler interferometer

Force Sensor

Mass 2 Mass 1

Air bearings

Beam deflection optics

• Measurement of inertial forces bylaser-Doppler interferometer



Moving surface

LDIReflected light

Speckle noise

Retro reflector

Moving surface

LDI0

-1Diffraction order

-2

Test grating (CD)


Speckle noise

Retro reflector

Test grating (CD)


Speckle noise


Speckle noise

Cr-Gitter on a Si-Plate (Wafer)

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Sinusoidal torqueprinciple of calibration


angular acceleration )(tϕ&&


rotational exciter

torque-transducer

air bearing

opt. radial grating

transducer signal A(t)

moment of inertia θ


opt. phase shift:1st order of diffraction

λ per line of grating

measurement:

digital quadrature analysis of the phase modulated Signals



Traceability:)()( ttT ϕθ &&⋅=

calibration:

TAS ˆˆ


angular acceleration )(tϕ&&

rotational exciter

torque-transducer

air bearing

opt. radial grating

transducer signal A(t)

moment of inertia θ


Sinusoidal TorqueCompensation of parasitic components



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The Current State of Vibration Metrology

in Germany

Dr. Thomas BrunsHead of the Working Groups

“Acceleration” and “Impact Dynamics”of the

Physikalisch-Technische Bundesanstalt

March 2006

Invited Visit to NMIJ / AIST (Tsukuba/Japan)

Thank you, for your attention!

the current state of – calibration facilities and...

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