ISO/TC 108/WG 34 - Calibration of vibration and shock transducers

This document details specifications for the instrumentation and methods to be used for testing fixed temperature sensitivity of vibration transducers. It applies to rectilinear velocity and acceleration transducers. The methods specified use both a comparison to a reference transducer and an absolute measurement by laser interferometer. This document is applicable for a frequency range from 10 Hz to 3 kHz (method-dependent), a dynamic range from 1 m/s2 to 100 m/s2 (frequency-dependent) and a temperature range from ?190 °C to 800 °C (method-dependent). Although it is possible to achieve these ranges among all the described systems, generally each has limitations within them. Method 1 (using a laser interferometer) is applicable to magnitude of sensitivity and phase calibration in the frequency range 10 Hz to 3 kHz at fixed temperatures (see Clause 7). Method 2 (using a reference transducer inside a chamber whose temperature limit is ?70 °C to 500 °C) can be used for magnitude of sensitivity and phase calibration in the frequency range 10 Hz to 1 kHz at fixed temperatures (see Clause 8). Method 3 (using a reference transducer outside the chamber) can only be used for the determination of the temperature response of complex sensitivity over a certain temperature range (see Clause 9). NOTE Method 1 and Method 2 can provide the deviation of complex sensitivity over a certain temperature range if the calibration is also done at the reference temperature (room temperature 23 °C ± 5 °C). To ensure the consistency of the use and test condition, the transducer, its cable and the conditioning amplifier are intended to be considered as a single unit and tested together.

This document specifies the instrumentation and procedure to be used for performing calibration of field vibration calibrators (FVCs). It is not applicable to FVCs used for the calibration of transducers. These are covered by ISO 16063‑21. Procedures and requirements of in situ calibration by FVC are beyond the scope of this document. Annex B provides more information on the application of FVC.

ISO 16063-33:2017 specifies a method, procedures and the specifications for an apparatus to be used for testing the magnetic field sensitivity of vibration and shock transducers. It is applicable to all kinds of vibration and shock transducers. ISO 16063-33:2017 is applicable for a reference test sinusoidal magnetic field having a root mean square (r.m.s.) value more than 10?3 T at 50 Hz or 60 Hz. Typically, a test magnetic field of 10?2 T at 50 Hz or 60 Hz is used. ISO 16063-33:2017 is primarily intended for those who are required to meet internationally standardized methods for the measurement of magnetic field sensitivity under laboratory conditions. NOTE 1 T (tesla) = 1 Wb/m2.

ISO 16063-45:2017 specifies the calibration of vibration transducers with built-in calibration coils in laboratory and in situ. In laboratory, the method described can be applied to calibrate the vibration sensitivity and electrical sensitivity, and to obtain the coefficient of calibration coil. In situ, it can be used to calibrate the electrical sensitivity and vibration sensitivity using electrical instrumentation. ISO 16063-45:2017 specifies the instrumentation and procedure for performing calibrations of vibration transducers with built-in calibration coils in the frequency range typically from 0,1 Hz to 100 Hz. The expanded uncertainty can be evaluated using the method given in this document.

ISO 16063-32:2016 lays down detailed specification for instruments and procedures of testing the frequency and the phase response of accelerometers by means of shock excitation. It applies to the accelerometers of the piezoelectric, piezoresistive and variable capacitance types with the damping ratio less than critical and in the frequency range up to 150 kHz. The method presumes that the frequency and the phase responses of the accelerometer under test gained by this method are the best possible characteristics for the mounted accelerometer on the condition that the recommendations for mechanical mounting of accelerometer stated in ISO 5348 are fulfilled and that the mass of the reference shock ball exceeds at least three times the mass of the accelerometer under test. Phase response of the accelerometer under test gained by this method is considered to be some "virtual" characteristic of accelerometer presuming that there is zero phase shift between the input and output signals at a frequency of 0 Hz. NOTE 1 It is intended that the user be aware that for the same accelerometer in the field application, the frequency and the phase responses might be different, depending on the mass and compliance of the test structure and the method of mounting. The method allows just a qualitative evaluation of the frequency and the phase response of accelerometers. NOTE 2 It is intended that the user does not try to get better resolution of the initial parts of the frequency and phase responses of the accelerometer under test than the dynamic range of the adequate characteristic provides it. The best use of the frequency and the phase responses of the accelerometer gained by this method are to get the best fit lines for the initial parts of the mentioned characteristics.

ISO 16063 comprises a series of documents dealing with methods for the calibration of vibration and shock transducers. ISO 16063-17:2016 lays down detailed specifications for the instrumentation and procedure to be used for primary calibration of accelerometers using centrifuge calibration. ISO 16063-17:2016 is applicable to rectilinear accelerometers with zero-frequency response, mainly of the strain gauge or piezoresistive type, and to primary standard and working transducers. It is applicable for a calibration range from 10 m/s2 to 20 000 m/s2 (higher accelerations possible) at 0 Hz. The limits of uncertainty applicable are ±1 % of reading.

ISO 16063-43:2015 prescribes terms and methods on the estimation of parameters used in mathematical models describing the input/output characteristics of vibration transducers, together with the respective parameter uncertainties. The described methods estimate the parameters on the basis of calibration data collected with standard calibration procedures in accordance with ISO 16063‑11, ISO 16063‑13, ISO 16063‑21 and ISO 16063‑22. The specification is provided as an extension of the existing procedures and definitions in those International Standards. The uncertainty estimation described conforms to the methods established by ISO/IEC Guide 98‑3 and ISO/IEC Guide 98‑3:2008/Supplement 1: 2008. The new characterization described in this document is intended to improve the quality of calibrations and measurement applications with broadband/transient input, like shock. It provides the means of a characterization of the vibration transducer's response to a transient input and, therefore, provides a basis for the accurate measurement of transient vibrational signals with the prediction of an input from an acquired output signal. The calibration data for accelerometers used in the aforementioned field of applications should additionally be evaluated and documented in accordance with the methods described below, in order to provide measurement capabilities and uncertainties beyond the limits drawn by the single value characterization given by ISO 16063‑13 and ISO 16063‑22.

ISO 16063-42:2014 specifies the instrumentation and procedure to be used for the accurate calibration of seismometer sensitivity using local gravitational acceleration (local Earth's gravitation; local value for the acceleration due to the Earth's gravity) as a reference value. It is intended generally to be applied to a servo-type accelerometer with/without a velocity output, which usually has a mass position output in the category of a wide-band seismometer with a bandwidth from 0,003 Hz to 100 Hz. The method specified enables the user to obtain static sensitivity for the seismometers up to 10−5 m/s2 (which corresponds to 1 mGal and approximately 1 ppm of the gravitational acceleration). The intended end-usage of the seismometer to be applied is: a) measurement and observation for the earth science including geophysics usage; b) measurement and observation for disaster prevention, such as detecting the precursor of a land slide; c) diagnosis for the soundness of a building structure and foundation soil in civil engineering; d) observation for nuclear-test detection.

ISO 16063-16:2014 specifies the instrumentation and procedure to be used for performing primary calibration of accelerometers using Earth's gravitation. It is applicable to rectilinear accelerometers with DC (zero hertz frequency) response, such as straingauge, piezoresistive, variable capacitance, and servo accelerometer types. ISO 16063-16:2014 is applicable to the calibration of the magnitude of the sensitivity, referenced to the acceleration due to the local gravitation at 0 Hz. With the use of appropriate calibration equipment, ISO 16063-16:2014 can be applied to the calibration of the magnitude of the sensitivity, referenced to fractional parts of the acceleration due to the local gravitation at 0 Hz. The specification of the instrumentation used contains requirements on environmental conditions, as well as specific requirements for the apparatus to be used.

ISO 16063-41:2011 specifies the instrumentation and procedures for performing primary and secondary calibrations of rectilinear laser vibrometers in the frequency range typically between 0,4 Hz and 50 kHz. It specifies the calibration of laser vibrometer standards designated for the calibration of either laser vibrometers or mechanical vibration transducers in accredited or non-accredited calibration laboratories, as well as the calibration of laser vibrometers by a laser vibrometer standard or by comparison to a reference transducer calibrated by laser interferometry. The specification of the instrumentation contains requirements on laser vibrometer standards. Rectilinear laser vibrometers can be calibrated in accordance with ISO 16063-41:2011 if they are designed as laser optical transducers with, or without, an indicating instrument to sense the motion quantities of displacement or velocity, and to transform them into proportional (i.e. time-dependent) electrical output signals. These output signals are typically digital for laser vibrometer standards and usually analogue for laser vibrometers. The output signal or the reading of a laser vibrometer can be the amplitude and, in addition, occasionally the phase shift of the motion quantity (acceleration included). In ISO 16063-41:2011 the modulus calibration is explicitly specified.

ISO 16063-31:2009 specifies details of the instrumentation and methods to be used for transverse vibration sensitivity testing. It applies to rectilinear velocity and acceleration transducers. The methods and procedures specified in ISO 16063-31:2009 allow the determination of the sensitivity of a transducer to vibration in the plane perpendicular to its geometric axis of sensitivity. Because the magnitude of this transverse sensitivity can vary with the direction of the applied vibration, the various methods determine the maximum value. Using that value, the ratio of the transverse sensitivity to the sensitivity on the geometric axis of the transducer can be calculated. In addition, the angle at which the maximum transverse sensitivity occurs can be determined. The methods and techniques specified can be applied without re-mounting the transducer away from its mounting surface during the test, thus avoiding significant uncertainties often encountered in methods which require repeated mounting. The different methods specified use a single-axis vibration exciter, a two-axis vibration exciter or a tri-axial vibration exciter. Tri-axial vibration excitation allows the transverse sensitivity and the sensitivity on the geometric axis to be determined simultaneously, thus simulating application conditions where the transducer is exposed to multi-axial vibration. ISO 16063-31:2009 is applicable to a frequency range from 1 Hz to 5 kHz and for a dynamic range from 1 m/s2 to 1 000 m/s2 (frequency dependent) and from 1 mm/s to 1 m/s (frequency dependent). Although among all the systems specified it is possible to achieve these ranges, generally each has limitations permitting its use in much smaller ranges. The methods specified are by comparison both to a reference transducer and to a laser interferometer. The methods specified allow an expanded uncertainty of the transverse sensitivity (coverage factor k = 2) of 0,1 % or less to be achieved, if the expanded uncertainty is expressed as a percentage of the sensitivity of the test transducer in its sensitive axis.

ISO 16063-15:2006 specifies the instrumentation and procedures used for primary angular vibration calibration of angular transducers, i.e. angular accelerometers, angular velocity transducers and rotational angle transducers (with or without amplifier) to obtain the magnitude and the phase shift of the complex sensitivity by steady-state sinusoidal vibration and laser interferometry. The methods specified in ISO 16063-15:2006 are applicable to measuring instruments (rotational laser vibrometers in particular) and to angular transducers as defined in ISO 2041 for the quantities of rotational angle, angular velocity and angular acceleration. ISO 16063-15:2006 is applicable to a frequency range from 1 Hz to 1,6 kHz and a dynamic range (amplitude) from 0,1 rad/s2 to 1 000 rad/s2 (frequency-dependent). Calibration frequencies lower than 1 Hz (e.g. 0,4 Hz, which is a reference frequency used in other International Standards) and angular acceleration amplitudes smaller than 0,1 rad/s2 can be achieved using method 3A or method 3B specified in ISO 16063-15:2006, in conjunction with an appropriate low-frequency angular vibration generator. ISO 16063-15:2006 describes six methods. Method 1A ( fringe-counting, interferometer type A) and method 1B ( fringe-counting, interferometer type B) are applicable to the calibration of the magnitude of complex sensitivity in the frequency range of 1 Hz to 800 Hz and under special conditions, at higher frequencies. Method 2A (minimum-point method, interferometer type A) and method 2B (minimum-point method, interferometer type B) can be used for sensitivity magnitude calibration in the frequency range of 800 Hz to 1,6 kHz. Method 3A (sine-approximation method, interferometer type A) and method 3B (sine-approximation method, interferometer type B) can be used for magnitude of sensitivity and phase calibration in the frequency range of 1 Hz to 1,6 kHz. Methods 1A, 1B and 3A, 3B provide for calibrations at fixed angular acceleration amplitudes at various frequencies. Methods 2A and 2B require calibrations at fixed rotational angle amplitudes (angular velocity amplitude and angular acceleration amplitude vary with frequency).

ISO 16063-22:2005 specifies the instrumentation and procedures to be used for secondary shock calibration of rectilinear transducers, using a reference acceleration, velocity or force measurement for the time-dependent shock. The methods are applicable in a shock pulse duration range of 0,05 ms to 8,0 ms, and a dynamic range (peak value) of 100 m/s to 100 km/s2 (time-dependent). The methods allow the transducer shock sensitivity (i.e. the relationship between the peak values of the transducer output quantity and the acceleration) to be obtained. These methods are not intended for the calibration of dynamic force transducers used in modal analysis.

ISO 16063-21:2003 describes the calibration of rectilinear vibration transducers by comparison. Although it mainly describes calibration using direct comparison to a standard calibrated by primary methods, the methods described can be applied between other levels in the calibration hierarchy. ISO 16063-21:2003 specifies procedures for performing calibrations of rectilinear vibration transducers by comparison in the frequency range from 0,4 Hz to 10 kHz. It is primarily intended for those who are required to meet ISO standardized methods for the measurement of vibration under laboratory conditions, where the uncertainty of measurement is relatively small. It can also be used under field conditions, where the uncertainty of measurement may be relatively large. From knowledge of all significant sources of uncertainty affecting the calibration, the expanded uncertainty can be evaluated using the methods given in ISO 16063-21. It also covers the assessment of uncertainties for calibrations performed using a check standard.

This part of ISO 16063 specifies the instrumentation and procedures to be used for primary calibration of accelerometers using the reciprocity method and the SI system of units. It is applicable to the calibration of rectilinear accelerometers over a frequency range of 40 Hz to 5 kHz and a frequency-dependent amplitude range of 10 m/s2 to 100 m/s 2 and is based on the use of the coil of an electrodynamic vibrator as the reciprocal transducer. Calibration of the sensitivity of a transducer can be obtained using this part of ISO 16063 provided that the signal conditioner or amplifier used with the transducer during calibration has been adequately characterized. In order to achieve these measurement uncertainties, it has been assumed that the transducer has been calibrated in combination with its signal conditioner or amplifier (the combination of which in this part of ISO 16063 is referred to as the accelerometer).

This part of ISO 16063 specifies the instrumentation and procedure to be used for primary vibration calibration of rectilinear accelerometers (with or without amplifier) to obtain magnitude and phase lag of the complex sensitivity by steady-state sinusoidal vibration and laser interferometry. It is applicable to a frequency range from 1 Hz to 10 kHz and a dynamic range (amplitude) from 0,1 m/s2 to 1 000 m/s2 (frequency-dependent). These ranges are covered with the uncertainty of measurement specified in clause 2. Calibration frequencies lower than 1 Hz (e.g. 0,4 Hz, which is a reference frequency used in other International Standards) and acceleration amplitudes smaller than 0,1 m/s2 (e.g. 0,004 m/s2 at 1 Hz) can be achieved using Method 3 specified in this part of ISO 16063, in conjunction with an appropriate low-frequency vibration generator. Method 1 (fringe-counting method) is applicable to sensitivity magnitude calibration in the frequency range 1 Hz to 800 Hz and, under special conditions, at higher frequencies (cf. clause 7). Method 2 (minimum-point method) can be used for sensitivity magnitude calibration in the frequency range 800 Hz to 10 kHz (cf. clause 8). Method 3 (sine-approximation method) can be used for magnitude of sensitivity and phase calibration in the frequency range 1 Hz to 10 kHz (cf. clause 9). Methods 1 and 3 provide for calibrations at fixed acceleration amplitudes at various frequencies. Method 2 requires calibrations at fixed displacement amplitudes (acceleration amplitude varies with frequency).

Lays down detailed specifications for the instrumentation and procedures to be used for accelerometer resonance testing. Does apply to rectilinear accelerometers of the piezoresistive, piezoelectric and variable capacitance types in the frequency range 50 Hz to 200 kHz.

Lays down detailed specifications for the instrumentation and procedure to be used for primary calibration of accelerometers using centrifuge calibration. Applies to all types of rectilinear accelerometers, primary standards and working pick-ups. Is applicable for a frequency range from 0,7 Hz to 10 Hz and a dynamic range from 10 m/s^2 to 100 m/s^2. The limits of uncertainty applicable are ± 2 % of reading.

Lays down detailed specifications for the instrumentation and procedure to be used for transverse shock sensitivity testing. Applies to rectilinear accelerometers of the strain gauge, piezoresistive and piezoelectric type. Is applicable for a time range from 0,01 ms to 10 ms and a dynamic range from 100 m/s^2 to 10^5 m/s^2. The limits of uncertainty applicable are ± 20 % of reading.

Lays down detailed specifications for the instrumentation and procedure to be used for acoustic sensitivity testing. Applies to accelerometers. Is applicable for a frequency range of random noise from 125 Hz to 8000 Hz and a sound pressure level of 130 dB (reference value: 2 × 10^-5 Pa).

Lays down detailed specifications for the instrumentation and procedure to be used for transient temperature sensitivity testing. Applies to piezoelectric pick-ups, whereby pick-up output due to sudden temperature change is measured.

Lays down detailed specifications for the instrumentation and procedure to be used for mounting torque sensitivity testing. Applies to pick-ups mounted by screws, bolts or other threaded fasteners. The change in calibration factor due to the mounting torque is determined. Is applicable for a mounting torque range of one-half of the specified value, the specified value und twice the value of the specified mounting torque.

Lays down detailed specifications for the instrumentation and procedure to be used for base strain sensitivity testing. Applies to rectilinear accelerometers, mainly of the piezoelectric type. Is applicable for the following parameters: reference values - pick-up base radius of curvature: 25 m, base strain: 2,5 × 10^-4; check values - radius of curvature 62,5 m, strain of base 1 × 10^-4; radius of curvature 12,5 m, strain of base 5 × 10^-4.

Lays down detailed specifications for the instrumentation and procedure to be used for fixed temperature sensitivity testing. Applies to rectilinear pick-ups. Is applicable for the following parameters: frequency range: 20 Hz to 1250 Hz; dynamic range: 0,1 µm to 10 mm (frequency-dependent), 1 mm/s to 1 m/s (frequency-dependent), 10 m/s^2 to 1000 m/s^2 (frequency-dependent); temperature range: - 45 °C to + 800 °C. The uncertainty applicable is ± 10 % of reading.

Lays down detailed specifications for the instrumentation and procedure to be used for magnetic field sensitivity testing. Applies to all kinds of pick-ups, whereby the pick-up output due to applied magnetic field is determined. Is applicable for a reference magnetic field of 10^-3 T r.m.s. at 50 Hz or 60 Hz.