GB/T 20485.42-2018 English PDF

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GB/T 20485.42-2018: Methods for the calibration of vibration and shock transducers -- Part 42: Calibration of seismometers with high accuracy using acceleration of gravity
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Basic data

Standard ID: GB/T 20485.42-2018 (GB/T20485.42-2018)
Description (Translated English): Methods for the calibration of vibration and shock transducers -- Part 42: Calibration of seismometers with high accuracy using acceleration of gravity
Sector / Industry: National Standard (Recommended)
Classification of Chinese Standard: N71
Classification of International Standard: 17.160
Word Count Estimation: 14,171
Date of Issue: 2018-03-15
Date of Implementation: 2018-10-01
Issuing agency(ies): State Administration for Market Regulation, China National Standardization Administration

GB/T 20485.42-2018: Methods for the calibration of vibration and shock transducers -- Part 42: Calibration of seismometers with high accuracy using acceleration of gravity

---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Methods for the calibration of vibration and shock transducers--Part 42. Calibration of seismometers with high accuracy using acceleration of gravity ICS 17.160 N71 National Standards of People's Republic of China Vibration and shock sensor calibration method Part 42. High-precision seismometers Gravity acceleration calibration Part 42. Calibrationofseismometerswithhighaccuracy (ISO 16063-42.2014, IDT) Published on.2018-03-15 2018-10-01 implementation General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China China National Standardization Administration issued

Content

Foreword III 1 Scope 1 2 Normative references 1 3 Traceability of measurement 1 4 Determination of local gravity value 1 4.1 Method of using absolute gravimeter 1 4.2 Method of using gravity acceleration normalization net and relative gravimeter 1 4.3 Method of using gravity acceleration standardization network 2 5 Equipment and environmental conditions requirements 2 5.1 Calibration Environment 2 5.2 Basic and vibration environment (isolation block of calibration equipment) 2 5.3 voltmeter 2 5.4 Adjustable Low Pass Filter 2 5.5 Power supply 2 5.6 tilting table 2 6 Method 3 6.1 Calibration principle 3 6.2 Calibration procedure 4 7 Results Statement 5 Appendix A (Normative) Calibration Uncertainty of Expression 6 Appendix B (informative) Traceability of seismometer calibration measurements 7 Reference 8

Foreword

GB/T 20485 "Vibration and Shock Sensor Calibration Method" mainly consists of basic concepts, absolute calibration, comparison calibration, environmental simulation It is composed of the other five categories, and the released parts are as follows. --- Part 1. Basic concepts; --- Part 11. Laser interference method vibration absolute calibration; --- Part 12. Reciprocal method vibration absolute calibration; --- Part 13. Absolute calibration of laser interference method; ---Part 15. Absolute calibration of angular vibration of laser interferometry; --- Part 16. Calibration of the Earth Gravity Method; --- Part 21. Vibration comparison method calibration; --- Part 22. Impact comparison method calibration; --- Part 31. Lateral vibration sensitivity test; --- Part 33. Magnetic sensitivity test; --- Part 41. Laser vibrometer calibration; --- Part 42. Gravity acceleration calibration of high precision seismometers. The parts that are planned to be released are. --- Part 17. Absolute calibration by centrifuge method; --- Part 32. Accelerometer frequency and phase response tests in response to test impulse excitation methods; --- Part 43. Accelerometer calibration based on model parameter identification; --- Part 44. Field vibration calibrator calibration; --- Part 45. Vibration sensor calibration with built-in calibration coils. This part is the 42nd part of GB/T 20485. This part is drafted in accordance with the rules given in GB/T 1.1-2009. This part uses the translation method equivalent to ISO 16063-42.2014 "Vibration and shock sensor calibration method Part 42. High precision Gravity Acceleration Calibration of Seismometers. This part is proposed and managed by the National Technical Committee for Standardization of Mechanical Vibration, Shock and Condition Monitoring (SAC/TC53). This section drafted by. China Institute of Metrology, Institute of Engineering Mechanics of China Earthquake Administration, Shaanxi Institute of Metrology. The main drafters of this section. Yu Mei, Yang Lifeng, Yang Qiaoyu, Yang Zhenyu, Qin Yu. Vibration and shock sensor calibration method Part 42. High-precision seismometers Gravity acceleration calibration

1 Scope

This part of GB/T 20485 specifies the use of local gravitational acceleration (local gravitational force; local acceleration generated by Earth's gravity) Degree value) As a reference value, instruments and procedures for accurate calibration of seismometer sensitivity. This section applies to servo-type accelerometers with or without speed signal output, which usually have a mass position output, and the bandwidth is Broadband seismometers from 0.003 Hz to 100 Hz. The method specified in this section allows the user to obtain orders of magnitude as low as 1 x 10-5 m/s2 (equivalent to 1 mGal and approximately 1 x 10-6 gravity acceleration) The static sensitivity of the seismometer. The acceleration expansion uncertainty (k=2) obtained by the present method is 1 × 10 -6 m/s 2 (0.1 mGal). When using the instructions described in this section In the case of an absolute gravimeter, the measurement uncertainty of acceleration can be reduced to within 5 × 10-8 m/s2 (5 μGal). Not counted by the device under test (DUT) introduced uncertainty, the relative expansion uncertainty of the calibration is 0.5%. The intended use of the seismometer is as follows. a) Earth science observations including geophysical applications; b) disaster prevention, such as monitoring of landslide precursors; c) reliability diagnosis of building structures and foundations in civil engineering; d) Nuclear test monitoring.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article. Pieces. For undated references, the latest edition (including all amendments) applies to this document. IGSN-71, Moreli, Carlo, ed., 1974. International Gravity Standardization Network 1971. Special Publications of the International Association of Geodesy No.4,194p

3 Traceability of measurement

See Appendix B for traceability of measurements in this method.

4 Determination of local gravity value

4.1 Method of using absolute gravimeter Determine the local absolute gravitational acceleration using a free fall absolute gravimeter (FG5 or other device). The local weight obtained thereby The extended uncertainty of the force acceleration is approximately 5×10-8 m/s2 (5 μGal). 4.2 Method of using gravity acceleration normalization net and relative gravimeter At the local gravity acceleration reference point established by IGSN-71, a relative gravimeter can be used to determine the local absolute gravity acceleration. degree. In this case, there is no need to correct the latitude and altitude. The extended uncertainty value of the relative gravimeter is given by the manufacturer. National Geological Exploration Institute, Meteorological Institute, Geodesy or Geophysics Institute can provide uncertainty than IGSN-71 Smaller gravitational acceleration measurements. This value can be used if possible. 4.3 Method of standardizing the net using gravity acceleration Based on the latitude and altitude of the measurement point, the local gravity acceleration can pass the nearest relative geographic point given in the IGSN-71 database. The value is calculated. The uncertainty of the local gravity acceleration thus obtained is approximately 1 x 10-5 m/s2 (1 mGal). This method is only applicable to no He is a situation with irregular terrain. National Geological Exploration Institute, Meteorological Institute, Geodesy or Geophysics Institute can provide uncertainty than IGSN-71 Smaller gravitational acceleration measurements. This value can be used if possible. Since the 1m height difference is equivalent to a gravitational acceleration change of about 3×10-6m/s2 (0.3mGal), the uncertainty of the height difference measurement is uncertain. The degree should be less than 2m. Note 1. The effect of the 1° deviation at a latitude of approximately 45° corresponds to a change in gravitational acceleration of approximately 1 × 10 -6 m/s 2 (0.1 mGal). Note 2. The local gravity map includes the geoid and altitude values.

5 Equipment and environmental conditions requirements

5.1 Calibration environment Standard reference atmospheric conditions. temperature (23 ± 3) ° C; relative humidity is not more than 75%. Temperature, humidity and atmospheric pressure should be measured and reported The report is given. 5.2 Basic and vibration environment (isolation block of calibration equipment) The calibration equipment should be placed on a sufficiently heavy basis to effectively isolate the vibrations of the building. 5.3 voltmeter The voltmeter that measures the voltage output of the seismometer should contribute no more than 0.1% to the measured relative extended uncertainty (see Table A.1). 5.4 Adjustable low pass filter a) cutoff frequency The cutoff frequency should be 10 Hz, 30 Hz or 60 Hz. A typical cutoff frequency is 30 Hz. b) attenuation rate (filter steepness) The attenuation or insertion loss in the filter stopband should be no less than 24dB/octave. 5.5 Power supply When measuring the sensitivity of a seismometer under certain gain conditions, the stability and signal-to-noise ratio of the power supply should meet the nominal measurement uncertainty. The rate of contribution. 5.6 tilting table The angular resolution of the tilting table should be no more than 0.05°, and the contribution to the extended uncertainty should be less than 0.03°. Tilting table should have support Seismic meter quality with sufficient stiffness, small enough clearance and hysteresis, and sufficient linearity.

6 methods

6.1 Principle of calibration Figures 1 and 2 show schematic and operational examples of the calibration device. Description. 1---based; 2---platform; 3---seismometer; 4---filter; 5---voltmeter; 6---Environmental instrument (temperature and atmospheric pressure); 7---tilt table; 8---ground. Figure 1 Calibration device Description. 1---based; 2---platform; 3---seismometer; 4---ground. Figure 2 Example of applying arbitrary acceleration from the initial setting Place the tilting table on the platform, which should be rigidly connected to the base described in 5.2 to form the vibration isolating block of the calibration equipment. Vibration isolation block top surface The horizontal plane should be perpendicular to the local gravity field and the angular deviation from the horizontal plane should be less than 0.03°. Due to the deviation of the horizontal angle The amount of influence of the force component is about 10-7. The angular deviation of the horizontal plane should be measured with an inclinometer with sufficient resolution. On the tilting table, the vertical component of the acceleration aθv or the horizontal component aθh sensed by the seismometer is given by. Aθv=cosθ·g Aθh=sinθ·g (1) In the formula. θ---the inclination angle with the horizontal plane obtained when placing the inclined table, the unit is degree (°); g---Local gravitational acceleration in meters per square second (m/s2). The vertical and horizontal components in the seismometer output signal are given by equation (2). The measured seismometer output signal E is. E=Saθv B or E=Saθh B (2) In the formula. S --- Seismometer sensitivity calculation value, in volts per meter negative quadratic seconds [V/(m · s-2)]; Aθv or aθh---the accelerometer acceleration component of the accelerometer sensitive axis, in meters per square second (m/s2); B --- The calculated value of the output signal offset component in volts (V); E --- Seismometer output voltage measurement in volts (V). When θv or θh changes from θ1 to θn, the n measurements of the seismometer output signal are. E1=Saθ1 B E2=Saθ2 B (3) En=Saθn B The sensitivity S of the seismometer and the offset value B of the output are given by the following linear regression equations (4) and (5). S= N∑ i=1 aθiEi-∑ i=1 Aθi∑ i=1 Ei N∑ i=1 (aθi)2-(∑ i=1 Aθi)2 (4) B= i=1 (aθi)2∑ i=1 Ei-∑ i=1 aθiEi∑ i=1 Aθi N∑ i=1 (aθi)2-(∑ i=1 Aθi)2 (5) 6.2 Calibration procedure Place the seismometer on the tilting table so that its sensitive axis is aligned with the vertical axis. The angular deviation between the sensitive axis and the vertical axis should be less than 0.03°, after adjusting the setting accurately, it should be adapted to the ambient temperature for a period of time. Seismometers typically have an angular misalignment error relative to the sensitive axis due to the package housing, also referred to as housing alignment error. School The quasi-seismic timing, as described above, should adjust the direction axis of the measured acceleration input to coincide with the direction of the sensitive axis of the seismometer. Really here The sensitive axis is determined by obtaining the inclination of the seismometer's maximum output signal, otherwise the uncertainty of the housing alignment error should include the tilt The inclination of the inclined table is not determined. On the tilting table, the vertical component of the acceleration induced by the seismometer at the initial tilt angle aθv0 or horizontal Quantity aθh0. Aθv0=cosθ0·g or aθh0=sinθ0·g The necessary multiple measurements of the output are made at a certain sampling time interval. Output record at acceleration aθv0 or aθh0 will be applied Is V0. Then, the tilt angle is adjusted to θ1, and the vertical component aθv1 or the horizontal component aθh1 of the acceleration is. Aθv1=cosθ1·g or aθh1=sinθ1·g After setting the inclination of the tilting table, take measurements. Perform the necessary multiple output measurements at a certain sampling interval. See figure 2.

7 Results presentation

The calibration results that need to be described are as follows. --- Sensitivity S, given as described in 6.2, in volts per meter minus quadratic seconds [V/(m · s - 2)]; --- Expanding the uncertainty, expressed by the relative value of the described sensitivity, and giving the inclusion factor; ---Applied acceleration in meters per square second (m/s2); --- Determine the method of local gravity acceleration and the uncertainty of evaluation, see Chapter 4; ---Environment, temperature, humidity and atmospheric pressure during measurement; --- Measurement method, using horizontal platform and additional tilting table method; ---Filter settings; ---Number of measurements.

Appendix A

(normative appendix) Calibrated measurement uncertainty expression The extended uncertainty U(S) of the calibration is given by. U(S)=ku(S) (A.1) Where k is the inclusion factor (usually 2) and u(S) is the synthetic relative uncertainty. The relative uncertainty of synthesis is given by. u(S)= S ∑ U2i(S) (A.2) Ui(S) is the uncertainty component that affects sensitivity, where Table A.1 lists the introduction of each possible component. Table A.1 Sources of uncertainty Standard uncertainty component u(xi) Source of uncertainty Uncertainty contribution Ui(y) 1 u(u^g) Uncertainty of local gravity acceleration measurement u1(S) 2 u(u^v) voltmeter measurement uncertainty u2(S) 3 u(u^av) Tilting platform angle setting introduces uncertainty (including by sensitive shaft and vertical Uncertainty introduced by the deviation of the straight axis angle) U3(S) 4 u(u^ah) Tilting platform angle setting introduces uncertainty (including by sensitive shaft and water) Uncertainty introduced by the deviation of the flat axis angle) U4(S) 5 u(u^e) Uncertainty introduced by repeatability measurements (including vibration noise and other uncertainties) Degree of uncertainty introduced by the source) U5(S) 6 u(u^asv) Tilting platform angle setting introduces uncertainty (including by the seismometer itself) Uncertainty introduced by the angular deviation of the sensitive axis from the vertical axis) U6(S) 7 u(u^ash) Tilting platform angle setting introduces uncertainty (including by the seismometer itself) The uncertainty introduced by the sensitive axis and the horizontal angle deviation) U7(S)

Appendix B

(informative appendix) Traceability of seismometer calibration measurements The traceability of the seismometer calibration measurement is shown in Figure B.1. Figure B.1 Traceability of measurements references [1] ISO 2041, Mechanicalvibration, shockandconditionmonitoring-Vocabulary [2] ISO 8042, Shockandvibrationmeasurements-Characteristicstobespecifiedforseismic Pick-ups [3] ISO 16063-1, Methods for the calibration of vibration and shock-translators-Part 1. Basicconcepts [4] ISO 5347-5.1993, Methods for thecalibrationofvibrationandshockpick-ups-Part 5. Cali- brationbyEarth'sgravitation [5] ISO /IEC Guide 98-3, Uncertaintyofmeasurement-Part 3. Guidetotheexpressionofun- Certaintyinmeasurement(GUM.1995)1) 1) ReissueoftheGuidetotheexpressionofuncertaintyinmeasurement (GUM),.1995. ......

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