Methods for the calibration of vibration and shock transducers - Part 11: Primary vibration calibration by laser interferometry
Some standard content:
1 Scope
GB/T 20485.11—2006/1S0 16063-11:1999 Calibration methods for vibration and shock sensors
Part 11: Absolute calibration of vibration by laser interferometry This part specifies the instrumentation and operating procedures for the absolute calibration of linear tangent accelerometers (with or without amplifiers), and the method for obtaining the amplitude and phase shift of the complex sensitivity of the accelerometer using steady-state sinusoidal vibration and laser interferometry. This part is applicable to the frequency range of 1 Hz to 10 kHz and the dynamic range (amplitude) of 0.1 m/s to 1 000 m/s (depending on the frequency)
The measurement uncertainty specified in Chapter 3 of this part exceeds the above range. If the calibration frequency is less than 1 Hz (e.g. 0.4 Hz in other international standards) and if the velocity amplitude is less than 0.1 m/3 (e.g. 0.004 m/s at 1 Hz), a suitable low-frequency polar motion table may be used and method 3 as specified in this standard may be used. Method 1 (fringe counting method) is applicable to the calibration of sensitivity amplitude in the frequency range of 1 Hz to 800 Hz. Under special conditions, it can be used for higher frequencies (see Chapter 8). Method 2 (minimum point method) is applicable to the calibration of sensitivity amplitude in the frequency range of 800 Hz to 10 kHz (see Chapter 9). Method 3 (sine approximation method) is applicable to the calibration of sensitivity amplitude and phase shift in the frequency range of 1 Hz to 10 kHz (see Chapter 10).
Methods 1 and 3 require calibration at different frequencies and fixed acceleration amplitudes: Method 2 requires calibration at fixed displacement amplitudes (where the velocity amplitude varies with frequency). 2 Normative references
The clauses in the following documents become clauses of this part through reference in this part of GB 20485. For all referenced documents with dates, all subsequent amendments (excluding errata) or revisions are not applicable to this part. However, parties to agreements based on this part are encouraged to study whether the latest versions of these documents can be used. For all undated referenced documents, the latest versions are applicable to this part.
GB/T3240—1982 Common frequencies in mechanical measurement GB/T13823.1—2005 Calibration of vibration and shock sensors - Force method - Part 1: Basic concepts (1S016063-1:1998Y
1SO2041 Vibration and shock vocabulary
3 Measurement uncertainty
The measurement uncertainty achieved by applying this part is: a) Sensitivity amplitude
The uncertainty of the measured value under reference conditions is 0.5%; under non-reference conditions, the uncertainty of the measured value does not exceed 1% b) Sensitivity phase shift
Under reference conditions, the uncertainty of the measured value is 0.5°; under non-reference conditions, the uncertainty of the measured value does not exceed 1°. Recommended reference conditions are:
Frequency (Hz): 160, 80, 40, 16, 8 (or: angular frequency w = 1 000.500.250, 100, 50 rad / s); acceleration (m / s2) (acceleration amplitude or effective value): 100, 50, 20, 10, 5.2, 1. CB/T 20485. 11-2006/LS0 16063-11: 1999 The selection of amplifiers should take into account the influence of noise, distortion and cutoff frequency to achieve the best performance. Note: According to GB/T13823.1-2005, the measurement uncertainty is expressed as the expanded uncertainty of measurement (abbreviated as uncertainty). 4 Instrument and equipment requirements
4.1 General
In order to meet the measurement range in Chapter 1 and the uncertainty requirements in Chapter 3, this clause gives the recommended technical indicators of the required instruments and equipment.
It is allowed that some systems are only used for part of the above-mentioned measurement range. Different systems (such as vibration tables) are usually used to cover the entire frequency and dynamic range.
Note: The instruments and equipment described in this clause include all the instruments and equipment involved in the three calibration methods inserted in this section. The instruments and equipment used in specific methods have been separately noted (Figure 1, Figure 2, Figure 3). 4.2 Frequency generators and indicators
should meet the following characteristics requirements,
a) Frequency uncertainty: not more than 0_05% of reading b) Frequency stability: not more than ±0.05% of reading during measurement: c) Amplitude stability, not more than ±0.05% of reading during measurement. 4.3 Power amplifiers and vibration tables
should meet the following characteristics requirements:
a) Total harmonic distortion of acceleration: not more than 2%; Transverse, bending and swaying acceleration: should be small enough to avoid excessive impact on the calibration results. When the amplitude is large, especially in the low frequency range of 1/2 to 10 Hz, the lateral movement should be less than 1% of the required axial movement. In the frequency range of 10 Hz to 1 kHz, the maximum lateral movement allowed is 10% of the axial movement. When the frequency is higher than 1 kHz, the maximum lateral movement allowed is 20% of the axial movement. 6)
) AC noise and noise, at least 7% lower than the full-scale output. 7) Acceleration amplitude stability: It does not exceed ±0.05% of the reading during measurement. Minimum accelerometer base strain introduced by the mounting surface (see 4.15). 4.4 Vibration isolation blocks for vibration table and laser receiver In order to avoid excessive influence of relative motion caused by earth pulsation and reaction forces of the vibration table support structure on the calibration results, the vibration table and the detector should be mounted on the same large mass block or two different large mass blocks that play a vibrating role. If a single vibration isolation block is used, the mass should be at least 2000 times the mass of the moving part. The relative vibration caused between the gadget meter and the interferometer is less than 0.05%. If the mass of the vibration isolation block is small, the movement of the vibration block caused by the vibration table should be considered to minimize the influence of the ground disturbance. The vibration block used in the frequency range of 10kHz to 10kHz should be placed on a specially designed damping spring to minimize the uncertainty caused by the interference effect to less than 0.1%. 4.5 Laser
An oxygen laser emitting red light should be used. Under laboratory conditions (i.e., atmospheric pressure 100 kPa, temperature 23℃, relative humidity 50%), the laser wavelength is 0.632 81 μm, and this value is used in this section.
If the laser has an automatic or automatic air pressure compensation function, it should be set to zero or turned off. Other single-frequency lasers with known and stable wavelengths can also be selected. 4.6 Interferometer
A Michelson laser interferometer should be used, which has a photoelectric receiver that can detect the interferometric signal band and whose frequency response has the required bandwidth.
Wherein, the required maximum bandwidth can be calculated from the measured velocity amplitude m as follows: fma,=VmxX3.16X10°ml
For method 1 (see Figure 1) and method 2 (see Figure 2), an ordinary Michelson interferometer with a single photoelectric receiver can be used. Method 2
GB/T 20485. 11—2006/1SO 16063-11:1999 Method 3 (see Figure 3) requires an improved Michelson interferometer with orthogonal signal outputs and two photoelectric receivers to review the interferometric signal beam. The structure of the improved Michelson interferometer is shown in Figure 4. The quarter wave plate divides the incident linearly polarized light into two measuring beams with mutually perpendicular polarization directions and a phase difference of 90°. After interfering with the linearly polarized reference beam, the two orthogonal polarized beams are separated by appropriate optical devices [such as Wollaston prism or polarization beam splitter] and detected by two photodiodes. The offset of the two-way output amplitude of the improved Michelson interferometer should not exceed ±5%. The relative amplitude deviation should not exceed ±5%, and the deviation from the nominal angle of 90° should not exceed 25". To ensure these tolerances, appropriate methods should be used to adjust the offset, amplitude and angle deviation of the two-way interference signal.
When the displacement is large, it is difficult to ensure that the amplitude deviation of the two-way output signal of the improved Michelson interferometer does not exceed the above tolerance. In order to make it In accordance with the measurement uncertainty requirements in Chapter 3, the above tolerances must be maintained at least when the displacement is less than 2 μm. When the displacement is larger, the tolerance is allowed to be increased.
Example: When the displacement amplitude is 2.5 μm (i.e., the acceleration amplitude is 0.1 m/s at a rate of 1 Hz), the allowable error of the relative deviation of the storage and amplitude can be increased to ±10%, and the tolerance of the deviation from the nominal angle of 90° can be increased to ±20° (see 10.2-1). Note: The improved McElson lower instrument in methods 1, 2, and 3 can be replaced by other appropriate double-beam level instruments: such as the (improved) Mather-Zehnder interferometer.
4.7 The counter (used for method 1) shall meet the following characteristics:
Frequency range: 1 Hz to the maximum required frequency (typical value used is 20 MH2): a
b) Uncertainty: not more than 0.01% of the reading. A frequency ratio counter with phase uncertainty may be used instead of the counter. 4.8 Tunable bandpass filter or spectrum analyzer (used for method 2) shall meet the following characteristics:
Frequency range: 800 Hz10 kHz;
b) Bandwidth: less than 12% of the center frequency; Filter slope: greater than 24 dB/0ct
Signal-to-noise ratio: greater than 70 dB when the signal is maximum: d
Dynamic range: increased by 60 dB.
4. 9 Zero value detector (for method 2)
A zero value detector with a frequency range of 800 Hz to 10 kHz should be used (if a harmonic analyzer is used in method 2, this instrument is not required). The frequency range of the instrument should meet the requirements for detecting the output noise of the bandpass filter. 4.10 The true RMS voltmeter of the output of the measuring plate accelerometer should meet the following special requirements:
a) Frequency range: 1 Hz to 10 kHz;
b) Uncertainty: not more than 0.1% of the reading. Multiply the RMS value by factor -/2 to obtain the signal amplitude (single peak value) in the calculation formula. For methods 1 and 2, an RMS voltmeter should be used. For method 3, a special voltage measuring instrument should be used according to 4.13; an RMS voltmeter can be used (optional). 4.11 Distortion Meter
The distortion meter should be able to measure the total harmonic distortion much less than 1% to 5% and meet the following characteristics: 8) Frequency range: 1Hz~10kHz, able to measure up to 5 harmonics, b) Uncertainty: when the distortion range is 0.5%~5%, it does not exceed 10% of the reading 4.12 Oscilloscope (optional)
An oscilloscope with a frequency range from 1Hz to the high frequency end and a minimum of 2MH2 can be used to determine the best characteristics of the interferometer and check the waveforms of the interferometer signal and the accelerometer signal. 4.13 Waveform recorder with computer interface (for method 3) A waveform recorder with computer interface can be used. The recorder has analog-to-digital conversion function and can store the two-way orthogonal output signal of the interferometer and the output signal of the accelerometer. Its amplitude resolution, sampling rate and storage capacity should be large enough to meet the uncertainties specified in Chapter 3 within the calibrated amplitude range. The amplitude resolution for the accelerometer output should generally be not less than 10 bits, and the resolution for the interferometer orthogonal output signal should be not less than 8 bits. Use a two-channel waveform recorder to record the interferometer output signal, and another waveform recorder (with higher resolution and lower sampling rate) to record the accelerometer output signal. In any case, data acquisition of the interferometer and accelerometer output signals should start and end at the same time, and their uncertainties should be such that the measurement uncertainty of the calibration meets the requirements of Chapter 3.
When the speed is maximum, the synchronization of the interferometer output signal is shortest. In the shortest period, sufficient number of sampling points should be ensured (in accordance with the provisions of 10.3). For a given acceleration amplitude, when the frequency is reduced, the displacement amplitude will increase accordingly, which requires the recorder to have a higher sampling rate and larger memory. If the above requirements cannot be met, the acceleration amplitude should be reduced. Example: When calibrating the accelerometer under the conditions of vibration frequency of 1 Hz and acceleration amplitude of 0.1 m/s, if the sampling rate is not less than 512 kHz, the storage capacity should be not less than 4 M bytes.
4.14 Computer with data processing program (for method 3) A computer with a data processing program should be used. The program should be compiled according to the calculation process described in 10.4. 4.15 Other requirements
In order to obtain the required measurement uncertainty of 0.5%, it is recommended to calibrate the accelerometer and the amplifier used with it as a whole.
The accelerometer should be a rigid structure. When calculating the measurement uncertainty, the base strain sensitivity, the lateral sensitivity and the stability of the accelerometer and amplifier combination should be considered (see Annex A). When calibrating the sensitivity (amplitude and/or phase shift) of the back-to-back reference accelerometer, a simulated mass block should be installed. The mass of the dummy mass should be the same as the mass disk of the accelerometer to be calibrated when mounted back-to-back on the reference accelerometer during the comparison calibration. The mass of the dummy mass is usually 20 g. The laser spot can be irradiated on the top (outer surface) of the dummy mass or on the upper surface of the reference accelerometer. If the motion of the top of the dummy mass is to be detected, the top of the mass disk should be a polished surface and the laser spot should be located close to the geometric center of the surface. If the motion of the mass cannot be regarded as a rigid body, the relative motion of the top and bottom surfaces should be considered. To simulate a typical standard accelerometer with a mass of 20 g, a hexagonal steel specimen with a length of 12 mm and a width of 16 mm should be used, with both the upper and lower surfaces being hexagonal. For example, at a frequency of 5 kHz, the relative motion introduces a systematic error of 0.26% in amplitude measurement and a systematic error of 4.2° in phase shift measurement.
If the upper surface movement of the reference accelerometer is detected by simulating the longitudinal through hole on the mass block, acoustic resonance may be generated in the hole at certain special frequency points, which will affect (increase) the measurement uncertainty of these frequency points and their adjacent frequency points. This should be taken into account when calculating the uncertainty.
5 Environmental conditions
Calibration should be carried out under the following environmental conditions: a) Indoor temperature: (23 ± 3);
6) Relative humidity: not more than 75%,
Care should be taken to avoid the influence of external vibration and noise on the measurement results. 6 Preferred acceleration and frequency values
The acceleration (amplitude or effective value) and frequency that uniformly cover the working range of the accelerometer should be preferably selected according to the following series of values: a) Acceleration value (method 1 and method 3), m/s: ——0.1, 0.2, 0.5, 12, 5, 10, 2050, 100, 200, 500, 1000 (1000m/s is only applicable to the measurement of sensitivity amplitude); b) Frequency, Hz:
In the range of 1Hz--10kHz, select according to the 1/3 octave frequency series of GB/I3240-1982 standard (or the angular frequency series calculated from a-1000rad/s). 4
Common procedures for the three methods
GB/T 20485.11--2006/ISD 16063-11:1999 For each frequency and acceleration combination, the distortion, lateral, bending and pendulum accelerations, hum and noise should be controlled to appropriate levels to meet the uncertainty requirements in Chapter 3 (see 4.3). The amplifier settings (gain and frequency range) used with the accelerometer should be set and recorded in accordance with the calibration requirements. 8 Method 1; Fringe counting method
8.1 General
This method is applicable to the calibration of accelerometer sensitivity amplitudes in the frequency range of 1 Hz to 800 Hz. Note: Method 1 can also be applied to calibrations at higher frequencies if the quantization error is reduced by special methods (see references [2] and [4]). At a given accelerometer amplitude (e.g. 100 m/s), this method can achieve higher frequency calibration. 8.2 Measurement steps
After adjusting the laser interferometer to the optimal state (see 4.6), at the required vibration frequency acceleration value (see Chapter 6), the sensitivity of the accelerometer is determined by using a counter (4.7) to measure the interference fringe frequency (using the fringe counting method of Figure 1), or using a frequency ratio counter (4.7) to measure the ratio of the interference fringe frequency and the vibration frequency. t
Frequency generator (4.2);
Power amplifier (4.3);
3--Stand (4.3);
一Travel platform moving part!
Simulation quality color block!
Accelerometer:
7—Amplifier;
8—Thousand-part instrument (4.6)
Laser (4.5>+
一Photoelectric receiver;
Problem ratio counter (4.7) 1
Counter (or frequency ratio counter) (4.7): Voltmeter (4.10);
Distortion meter (4.11);
Oscilloscope (4.12)
Figure 1 Fringe counting method (method 1) Measurement system 5
GB/T 20485. 11—2006/IS0 16063-11: 19998.3 Expression of measurement results See B1 of Record B. The acceleration amplitude of the accelerometer, expressed in m/s, is calculated from the reading of the interference fringe rate: a = f, ×3. 123 × 10-m. The sensitivity (amplitude) S, expressed in V/(m·s-3), is calculated by the Yamashita formula: m × 0.3202 × 10m*l. In this formula,
is the voltage amplitude output by the accelerometer;
is the vibration frequency of the vibration table;
is the interference fringe frequency, that is, the number of interference fringes recorded in a sufficiently long time period divided by the time interval. If a frequency ratio counter is used, the acceleration amplitude a, expressed in m/s*, is calculated by the following formula: 4 = R, × 3. 123 × 10 -m
Sensitivity (amplitude) S, expressed in V/(ms-), is calculated by the following formula: s
Where:
X 0. 320 2 X 10°m -I
（4）
（5）
The ratio of the interference fringe frequency f, to the vibration frequency f, over a sufficient number of vibration cycles (depending on the grip frequency, for example at least 100 vibration cycles at 160 Hz). The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9 Method 2: Minimum point method
9.1 General
This method is applicable to the calibration of the sensitivity amplitude of accelerometers in the frequency range of 800 F-Iz to 10 k[z. The method described in this clause uses the white displacement corresponding to the point of the first-order Bessel function of the first kind to determine the displacement (see B.2 in Appendix B). The equivalent method of using the value of the independent variable corresponding to the zero point of the first-order Bessel function of the first kind can also be used to determine the displacement. However, the latter requires the modulation of the reference mirror (see reference [5]).
9.2 Measurement procedure
The output signal of the photoelectric receiver (4.6) is filtered with a bandpass filter (4.8) whose center frequency is equal to the vibration table frequency. The signal obtained after filtering contains a series of minimum points of the accelerometer displacement amplitude, see Table 1. Set the calibration frequency and then adjust the vibration table amplitude from zero so that the filtered photoelectric detection signal reaches a maximum value and then returns to a minimum value. This minimum value is the first minimum point. The amplitude corresponding to this point is 0.1930 μm. The amplitudes corresponding to other minimum points can be found in Table 1. The measurement system of the minimum point method is shown in Figure 2. Note 1: The first-order zero-order Hcsscl function can also be used to determine the acceleration sensitivity. In this case, the reference mirror is excited with a frequency lower than the reference frequency, and the center frequency of the bandpass filter or frequency analyzer is adjusted to the excitation frequency of the reference mirror (see reference [6]). Note 2: The modulation of the reference mirror position can also be used to improve the efficiency of the first-order Bess minimum point method (see reference [7]). Table 1 Displacement amplitude corresponding to the small point (1 = 0.63281μm) Smallest point
Displacement amplitude 3/
Smallest point
Amplitude/
Smallest point
Displacement amplitude 5/
2, 570 4
2. 728 64
Table 1 (continued)
GB/T 20485. 11—2006/ISO 16063-11: 1999 Smallest point
The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9.3 Expression of measurement results
See also B.2 in Closed Note B.
1—frequency generator (4.2);
-power amplifier (4.3)
vibration table (4.3);
—moving part of the vibration table:bZxz.net
5—mold disk block:
—frequency analyzer;
—amplifier:
-interferometer (4.6)1
9—laser (4.5),
photoelectric receiver:
frequency analyzer (4.8);
displacement amplitude 3/
—bandpass filter tunable according to vibration frequency (4.8)12
—voltmeter:
voltmeter (4,10)
15—distortion meter (4. 11),
oscilloscope (4.12).
Figure 2 Minimum point method (method 2) Tidal volume system
GB/T20485.11—2006/IS016063-11:1999 Acceleration amplitude t, expressed in m/s, is calculated by the following formula: 2 = 39, 478 X 3F2
Sensitivity (V/m·s-\) is expressed by the following formula: S = 0. 025 33 X
In the formula;
-amplitude of the output voltage of the accelerometer:
-displacement amplitude corresponding to each minimum point in Table 1; frequency of the vibration table.
10 Method 3: Sine approximation method
10.1 General
This method is applicable to the calibration of the sensitivity amplitude and (or) phase shift of accelerometers with a frequency range of 1 Hz to 10 kHz. 10.2 Measurement steps
Install the alarm according to Figures 3 and 4
(7)
Adjust the laser interferometer (Figure 4, for example) so that its output is two phase-orthogonal signals 2 and uz, and its tolerance meets the requirements of 4.6. After adjusting the interferometer (4.) to the best working state, measure the sensitivity amplitude and phase shift of the accelerometer according to the following steps under the specified vibration frequency and spherical amplitude (see Chapter 6). 1-Frequency generator (4.2):
2-Power amplifier (4.3);
Moving table (4.3)
Moving part of the vibration table 1
Analog mass block:
Accelerometer
Amplifier:
Interferometer (4.6):
Laser (4.5):
Photoelectric inspector:
Digital waveform recorder (4.13):
-Voltmeter (4.10);
Insulator (4.11);
Indicator (4.12).
Figure 3 Sine approximation method (Method 3 Measurement system GB/T20485.11-2006/[S0 16063-11:1999 Sinusoidal vibrations are applied to the accelerometer. The displacement amplitude should be large enough to produce at least one complete light and dark fringe in the interferometer output.
Go to 1: When the displacement value is not greater than 0.5 μm, the orthogonal output signal that meets the tolerance specified in 4.6 contains a variety of interference factors, the combined effect of which may cause the maximum error in the sensitivity value to be not less than 0.3% and the maximum error in the phase shift to be not less than 0.3°. This error can be reduced by adjusting to a tighter tolerance than 4.6 [see reference [8] or by using the correction procedure provided in reference []. Note 2: In order to achieve accurate measurement of the complex sensitivity and phase of the accelerometer within the nanometer displacement vibration range, the sinusoidal approach can be combined with a suitable heterodyne technique, see references [10_ and [11]. It can be calibrated off-frequency (e.g. 20 kHz).
Note 3: If the sinusoidal approximation method adopted by the frame has met the uncertainty requirements of Chapter 3, in order to improve the suppression efficiency of the quotient procedure, the position value or phase modulation value can be added and separated [12]-
Reference mirror
Vibration self-motion part:
3——Acceleration
1—-Simulation mass+
5-Beam splitter;
10.3Data acquisition
6.Polarizer;
-Optician;
8——Wolston prism:
9——Photoelectric receiver.
Figure 4 Orthogonal laser interferometer
The cutoff frequencies of the low-pass filter and the high-pass filter (if used) should be set to keep the interference of the low-pass filter on the calibration results within the tolerance range (see reference [). To satisfy the Naytsenter law, the sampling rate should be set so that the highest frequency is less than 1/2 of the sampling rate.
The analog-to-digital conversion of the accelerometer output voltage signal can be completed at the same or lower sampling rate as the analog-to-digital conversion rate of the interferometer output signal. The sampling of the three signals should start and end at the same time, and at least two of the output signals of the lower instrument should be synchronized with the same system clock.
should be sampled at tIt is expressed in V/(m·s-3) and calculated by the Yamashita formula: milli×0.3202×10m*l
, where
is the voltage amplitude output by the accelerometer;
is the vibration frequency of the vibration table;
is the interference fringe frequency, that is, the number of interference fringes recorded in a sufficiently long time period divided by the time interval. If a frequency ratio counter is used, the acceleration amplitude a, expressed in m/s*, is calculated by the following formula: 4 = R, × 3. 123 × 10 -m
Sensitivity (amplitude) S, expressed in V/(ms-), is calculated by the following formula: s
Where:
X 0. 320 2 X 10°m -I
（4）
（5）
The ratio of the interference fringe frequency f, to the vibration frequency f, over a sufficient number of vibration cycles (depending on the grip frequency, for example at least 100 vibration cycles at 160 Hz). The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9 Method 2: Minimum point method
9.1 General
This method is applicable to the calibration of the sensitivity amplitude of accelerometers in the frequency range of 800 F-Iz to 10 k[z. The method described in this clause uses the white displacement corresponding to the point of the first-order Bessel function of the first kind to determine the displacement (see B.2 in Appendix B). The equivalent method of using the value of the independent variable corresponding to the zero point of the first-order Bessel function of the first kind can also be used to determine the displacement. However, the latter requires the modulation of the reference mirror (see reference [5]).
9.2 Measurement procedure
The output signal of the photoelectric receiver (4.6) is filtered with a bandpass filter (4.8) whose center frequency is equal to the vibration table frequency. The signal obtained after filtering contains a series of minimum points of the accelerometer displacement amplitude, see Table 1. Set the calibration frequency and then adjust the vibration table amplitude from zero so that the filtered photoelectric detection signal reaches a maximum value and then returns to a minimum value. This minimum value is the first minimum point. The amplitude corresponding to this point is 0.1930 μm. The amplitudes corresponding to other minimum points can be found in Table 1. The measurement system of the minimum point method is shown in Figure 2. Note 1: The first-order zero-order Hcsscl function can also be used to determine the acceleration sensitivity. In this case, the reference mirror is excited with a frequency lower than the reference frequency, and the center frequency of the bandpass filter or frequency analyzer is adjusted to the excitation frequency of the reference mirror (see reference [6]). Note 2: The modulation of the reference mirror position can also be used to improve the efficiency of the first-order Bess minimum point method (see reference [7]). Table 1 Displacement amplitude corresponding to the small point (1 = 0.63281μm) Smallest point
Displacement amplitude 3/
Smallest point
Amplitude/
Smallest point
Displacement amplitude 5/
2, 570 4
2. 728 64
Table 1 (continued)
GB/T 20485. 11—2006/ISO 16063-11: 1999 Smallest point
The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9.3 Expression of measurement results
See also B.2 in Closed Note B.
1—frequency generator (4.2);
-power amplifier (4.3)
vibration table (4.3);
—moving part of the vibration table:
5—mold disk block:
—frequency analyzer;
—amplifier:
-interferometer (4.6)1
9—laser (4.5),
photoelectric receiver:
frequency analyzer (4.8);
displacement amplitude 3/
—bandpass filter tunable according to vibration frequency (4.8)12
—voltmeter:
voltmeter (4,10)
15—distortion meter (4. 11),
oscilloscope (4.12).
Figure 2 Minimum point method (method 2) Tidal volume system
GB/T20485.11—2006/IS016063-11:1999 Acceleration amplitude t, expressed in m/s, is calculated by the following formula: 2 = 39, 478 X 3F2
Sensitivity (V/m·s-\) is expressed by the following formula: S = 0. 025 33 X
In the formula;
-amplitude of the output voltage of the accelerometer:
-displacement amplitude corresponding to each minimum point in Table 1; frequency of the vibration table.
10 Method 3: Sine approximation method
10.1 General
This method is applicable to the calibration of the sensitivity amplitude and (or) phase shift of accelerometers with a frequency range of 1 Hz to 10 kHz. 10.2 Measurement steps
Install the alarm according to Figures 3 and 4
(7)
Adjust the laser interferometer (Figure 4, for example) so that its output is two phase-orthogonal signals 2 and uz, and its tolerance meets the requirements of 4.6. After adjusting the interferometer (4.) to the best working state, measure the sensitivity amplitude and phase shift of the accelerometer according to the following steps under the specified vibration frequency and spherical amplitude (see Chapter 6). 1-Frequency generator (4.2):
2-Power amplifier (4.3);
Moving table (4.3)
Moving part of the vibration table 1
Analog mass block:
Accelerometer
Amplifier:
Interferometer (4.6):
Laser (4.5):
Photoelectric inspector:
Digital waveform recorder (4.13):
-Voltmeter (4.10);
Insulator (4.11);
Indicator (4.12).
Figure 3 Sine approximation method (Method 3 Measurement system GB/T20485.11-2006/[S0 16063-11:1999 Sinusoidal vibrations are applied to the accelerometer. The displacement amplitude should be large enough to produce at least one complete light and dark fringe in the interferometer output.
Go to 1: When the displacement value is not greater than 0.5 μm, the orthogonal output signal that meets the tolerance specified in 4.6 contains a variety of interference factors, the combined effect of which may cause the maximum error in the sensitivity value to be not less than 0.3% and the maximum error in the phase shift to be not less than 0.3°. This error can be reduced by adjusting to a tighter tolerance than 4.6 [see reference [8] or by using the correction procedure provided in reference []. Note 2: In order to achieve accurate measurement of the complex sensitivity and phase of the accelerometer within the nanometer displacement vibration range, the sinusoidal approach can be combined with a suitable heterodyne technique, see references [10_ and [11]. It can be calibrated off-frequency (e.g. 20 kHz).
Note 3: If the sinusoidal approximation method adopted by the frame has met the uncertainty requirements of Chapter 3, in order to improve the suppression efficiency of the quotient procedure, the position value or phase modulation value can be added and separated [12]-
Reference mirror
Vibration self-motion part:
3——Acceleration
1—-Simulation mass+
5-Beam splitter;
10.3Data acquisition
6.Polarizer;
-Optician;
8——Wolston prism:
9——Photoelectric receiver.
Figure 4 Orthogonal laser interferometer
The cutoff frequencies of the low-pass filter and the high-pass filter (if used) should be set to keep the interference of the low-pass filter on the calibration results within the tolerance range (see reference [). To satisfy the Naytsenter law, the sampling rate should be set so that the highest frequency is less than 1/2 of the sampling rate.
The analog-to-digital conversion of the accelerometer output voltage signal can be completed at the same or lower sampling rate as the analog-to-digital conversion rate of the interferometer output signal. The sampling of the three signals should start and end at the same time, and at least two of the output signals of the lower instrument should be synchronized with the same system clock.
should be sampled at tIt is expressed in V/(m·s-3) and calculated by Yamashita's formula: milli×0.3202×10m*l
, where
is the voltage amplitude output by the accelerometer;
is the vibration frequency of the vibration table;
is the interference fringe frequency, that is, the number of interference fringes recorded in a sufficiently long time period divided by the time interval. If a frequency ratio counter is used, the acceleration amplitude a, expressed in m/s*, is calculated by the following formula: 4 = R, × 3. 123 × 10 -m
Sensitivity (amplitude) S, expressed in V/(ms-), is calculated by the following formula: s
Where:
X 0. 320 2 X 10°m -I
（4）
（5）
The ratio of the interference fringe frequency f, to the vibration frequency f, over a sufficient number of vibration cycles (depending on the grip frequency, for example at least 100 vibration cycles at 160 Hz). The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9 Method 2: Minimum point method
9.1 General
This method is applicable to the calibration of the sensitivity amplitude of accelerometers in the frequency range of 800 F-Iz to 10 k[z. The method described in this clause uses the white displacement corresponding to the point of the first-order Bessel function of the first kind to determine the displacement (see B.2 in Appendix B). The equivalent method of using the value of the independent variable corresponding to the zero point of the first-order Bessel function of the first kind can also be used to determine the displacement. However, the latter requires the modulation of the reference mirror (see reference [5]).
9.2 Measurement procedure
The output signal of the photoelectric receiver (4.6) is filtered with a bandpass filter (4.8) whose center frequency is equal to the vibration table frequency. The signal obtained after filtering contains a series of minimum points of the accelerometer displacement amplitude, see Table 1. Set the calibration frequency and then adjust the vibration table amplitude from zero so that the filtered photoelectric detection signal reaches a maximum value and then returns to a minimum value. This minimum value is the first minimum point. The amplitude corresponding to this point is 0.1930 μm. The amplitudes corresponding to other minimum points can be found in Table 1. The measurement system of the minimum point method is shown in Figure 2. Note 1: The first-order zero-order Hcsscl function can also be used to determine the acceleration sensitivity. In this case, the reference mirror is excited with a frequency lower than the reference frequency, and the center frequency of the bandpass filter or frequency analyzer is adjusted to the excitation frequency of the reference mirror (see reference [6]). Note 2: The modulation of the reference mirror position can also be used to improve the efficiency of the first-order Bess minimum point method (see reference [7]). Table 1 Displacement amplitude corresponding to the small point (1 = 0.63281μm) Smallest point
Displacement amplitude 3/
Smallest point
Amplitude/
Smallest point
Displacement amplitude 5/
2, 570 4
2. 728 64
Table 1 (continued)
GB/T 20485. 11—2006/ISO 16063-11: 1999 Smallest point
The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9.3 Expression of measurement results
See also B.2 in Closed Note B.
1—frequency generator (4.2);
-power amplifier (4.3)
vibration table (4.3);
—moving part of the vibration table:
5—mold disk block:
—frequency analyzer;
—amplifier:
-interferometer (4.6)1
9—laser (4.5),
photoelectric receiver:
frequency analyzer (4.8);
displacement amplitude 3/
—bandpass filter tunable according to vibration frequency (4.8)12
—voltmeter:
voltmeter (4,10)
15—distortion meter (4. 11),
oscilloscope (4.12).
Figure 2 Minimum point method (method 2) Tidal volume system
GB/T20485.11—2006/IS016063-11:1999 Acceleration amplitude t, expressed in m/s, is calculated by the following formula: 2 = 39, 478 X 3F2
Sensitivity (V/m·s-\) is expressed by the following formula: S = 0. 025 33 X
In the formula;
-amplitude of the output voltage of the accelerometer:
-displacement amplitude corresponding to each minimum point in Table 1; frequency of the vibration table.
10 Method 3: Sine approximation method
10.1 General
This method is applicable to the calibration of the sensitivity amplitude and (or) phase shift of accelerometers with a frequency range of 1 Hz to 10 kHz. 10.2 Measurement steps
Install the alarm according to Figures 3 and 4
(7)
Adjust the laser interferometer (Figure 4, for example) so that its output is two phase-orthogonal signals 2 and uz, and its tolerance meets the requirements of 4.6. After adjusting the interferometer (4.) to the best working state, measure the sensitivity amplitude and phase shift of the accelerometer according to the following steps under the specified vibration frequency and spherical amplitude (see Chapter 6). 1-Frequency generator (4.2):
2-Power amplifier (4.3);
Moving table (4.3)
Moving part of the vibration table 1
Analog mass block:
Accelerometer
Amplifier:
Interferometer (4.6):
Laser (4.5):
Photoelectric inspector:
Digital waveform recorder (4.13):
-Voltmeter (4.10);
Insulator (4.11);
Indicator (4.12).
Figure 3 Sine approximation method (Method 3 Measurement system GB/T20485.11-2006/[S0 16063-11:1999 Sinusoidal vibrations are applied to the accelerometer. The displacement amplitude should be large enough to produce at least one complete light and dark fringe in the interferometer output.
Go to 1: When the displacement value is not greater than 0.5 μm, the orthogonal output signal that meets the tolerance specified in 4.6 contains a variety of interference factors, the combined effect of which may cause the maximum error in the sensitivity value to be not less than 0.3% and the maximum error in the phase shift to be not less than 0.3°. This error can be reduced by adjusting to a tighter tolerance than 4.6 [see reference [8] or by using the correction procedure provided in reference []. Note 2: In order to achieve accurate measurement of the complex sensitivity and phase of the accelerometer within the nanometer displacement vibration range, the sinusoidal approach can be combined with a suitable heterodyne technique, see references [10_ and [11]. It can be calibrated off-frequency (e.g. 20 kHz).
Note 3: If the sinusoidal approximation method adopted by the frame has met the uncertainty requirements of Chapter 3, in order to improve the suppression efficiency of the quotient procedure, the position value or phase modulation value can be added and separated [12]-
Reference mirror
Vibration self-motion part:
3——Acceleration
1—-Simulation mass+
5-Beam splitter;
10.3Data acquisition
6.Polarizer;
-Optician;
8——Wolston prism:
9——Photoelectric receiver.
Figure 4 Orthogonal laser interferometer
The cutoff frequencies of the low-pass filter and the high-pass filter (if used) should be set to keep the interference of the low-pass filter on the calibration results within the tolerance range (see reference [). To satisfy the Naytsenter law, the sampling rate should be set so that the highest frequency is less than 1/2 of the sampling rate.
The analog-to-digital conversion of the accelerometer output voltage signal can be completed at the same or lower sampling rate as the analog-to-digital conversion rate of the interferometer output signal. The sampling of the three signals should start and end at the same time, and at least two of the output signals of the lower instrument should be synchronized with the same system clock.
should be sampled at t3202×10m*l
Wu Zhong,
is the voltage amplitude of the accelerometer output;
is the vibration frequency of the vibration table;
is the interference fringe frequency, that is, the number of interference fringes recorded in a sufficiently long time period divided by the time interval. If a frequency ratio counter is used, the acceleration amplitude a, expressed in m/s*, is calculated by the following formula: 4 = R, × 3. 123 × 10 -m
Sensitivity (amplitude) S, expressed in V/(ms-), is calculated by the following formula: s
Where:
X 0. 320 2 X 10°m -I
（4）
（5）
The ratio of the interference fringe frequency f, to the vibration frequency f, over a sufficient number of vibration cycles (depending on the grip frequency, for example at least 100 vibration cycles at 160 Hz). The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9 Method 2: Minimum point method
9.1 General
This method is applicable to the calibration of the sensitivity amplitude of accelerometers in the frequency range of 800 F-Iz to 10 k[z. The method described in this clause uses the white displacement corresponding to the point of the first-order Bessel function of the first kind to determine the displacement (see B.2 in Appendix B). The equivalent method of using the value of the independent variable corresponding to the zero point of the first-order Bessel function of the first kind can also be used to determine the displacement. However, the latter requires the modulation of the reference mirror (see reference [5]).
9.2 Measurement procedure
The output signal of the photoelectric receiver (4.6) is filtered with a bandpass filter (4.8) whose center frequency is equal to the vibration table frequency. The signal obtained after filtering contains a series of minimum points of the accelerometer displacement amplitude, see Table 1. Set the calibration frequency and then adjust the vibration table amplitude from zero so that the filtered photoelectric detection signal reaches a maximum value and then returns to a minimum value. This minimum value is the first minimum point. The amplitude corresponding to this point is 0.1930 μm. The amplitudes corresponding to other minimum points can be found in Table 1. The measurement system of the minimum point method is shown in Figure 2. Note 1: The first-order zero-order Hcsscl function can also be used to determine the acceleration sensitivity. In this case, the reference mirror is excited with a frequency lower than the reference frequency, and the center frequency of the bandpass filter or frequency analyzer is adjusted to the excitation frequency of the reference mirror (see reference [6]). Note 2: The modulation of the reference mirror position can also be used to improve the efficiency of the first-order Bess minimum point method (see reference [7]). Table 1 Displacement amplitude corresponding to the small point (1 = 0.63281μm) Smallest point
Displacement amplitude 3/
Smallest point
Amplitude/
Smallest point
Displacement amplitude 5/
2, 570 4
2. 728 64
Table 1 (continued)
GB/T 20485. 11—2006/ISO 16063-11: 1999 Smallest point
The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9.3 Expression of measurement results
See also B.2 in Closed Note B.
1—frequency generator (4.2);
-power amplifier (4.3)
vibration table (4.3);
—moving part of the vibration table:
5—mold disk block:
—frequency analyzer;
—amplifier:
-interferometer (4.6)1
9—laser (4.5),
photoelectric receiver:
frequency analyzer (4.8);
displacement amplitude 3/
—bandpass filter tunable according to vibration frequency (4.8)12
—voltmeter:
voltmeter (4,10)
15—distortion meter (4. 11),
oscilloscope (4.12).
Figure 2 Minimum point method (method 2) Tidal volume system
GB/T20485.11—2006/IS016063-11:1999 Acceleration amplitude t, expressed in m/s, is calculated by the following formula: 2 = 39, 478 X 3F2
Sensitivity (V/m·s-\) is expressed by the following formula: S = 0. 025 33 X
In the formula;
-amplitude of the output voltage of the accelerometer:
-displacement amplitude corresponding to each minimum point in Table 1; frequency of the vibration table.
10 Method 3: Sine approximation method
10.1 General
This method is applicable to the calibration of the sensitivity amplitude and (or) phase shift of accelerometers with a frequency range of 1 Hz to 10 kHz. 10.2 Measurement steps
Install the alarm according to Figures 3 and 4
(7)
Adjust the laser interferometer (Figure 4, for example) so that its output is two phase-orthogonal signals 2 and uz, and its tolerance meets the requirements of 4.6. After adjusting the interferometer (4.) to the best working state, measure the sensitivity amplitude and phase shift of the accelerometer according to the following steps under the specified vibration frequency and spherical amplitude (see Chapter 6). 1-Frequency generator (4.2):
2-Power amplifier (4.3);
Moving table (4.3)
Moving part of the vibration table 1
Analog mass block:
Accelerometer
Amplifier:
Interferometer (4.6):
Laser (4.5):
Photoelectric inspector:
Digital waveform recorder (4.13):
-Voltmeter (4.10);
Insulator (4.11);
Indicator (4.12).
Figure 3 Sine approximation method (Method 3 Measurement system GB/T20485.11-2006/[S0 16063-11:1999 Sinusoidal vibrations are applied to the accelerometer. The displacement amplitude should be large enough to produce at least one complete light and dark fringe in the interferometer output.
Go to 1: When the displacement value is not greater than 0.5 μm, the orthogonal output signal that meets the tolerance specified in 4.6 contains a variety of interference factors, the combined effect of which may cause the maximum error in the sensitivity value to be not less than 0.3% and the maximum error in the phase shift to be not less than 0.3°. This error can be reduced by adjusting to a tighter tolerance than 4.6 [see reference [8] or by using the correction procedure provided in reference []. Note 2: In order to achieve accurate measurement of the complex sensitivity and phase of the accelerometer within the nanometer displacement vibration range, the sinusoidal approach can be combined with a suitable heterodyne technique, see references [10_ and [11]. It can be calibrated off-frequency (e.g. 20 kHz).
Note 3: If the sinusoidal approximation method adopted by the frame has met the uncertainty requirements of Chapter 3, in order to improve the suppression efficiency of the quotient procedure, the position value or phase modulation value can be added and separated [12]-
Reference mirror
Vibration self-motion part:
3——Acceleration
1—-Simulation mass+
5-Beam splitter;
10.3Data acquisition
6.Polarizer;
-Optician;
8——Wolston prism:
9——Photoelectric receiver.
Figure 4 Orthogonal laser interferometer
The cutoff frequencies of the low-pass filter and the high-pass filter (if used) should be set to keep the interference of the low-pass filter on the calibration results within the tolerance range (see reference [). To satisfy the Naytsenter law, the sampling rate should be set so that the highest frequency is less than 1/2 of the sampling rate.
The analog-to-digital conversion of the accelerometer output voltage signal can be completed at the same or lower sampling rate as the analog-to-digital conversion rate of the interferometer output signal. The sampling of the three signals should start and end at the same time, and at least two of the output signals of the lower instrument should be synchronized with the same system clock.
should be sampled at t3202×10m*l
Wu Zhong,
is the voltage amplitude of the accelerometer output;
is the vibration frequency of the vibration table;
is the interference fringe frequency, that is, the number of interference fringes recorded in a sufficiently long time period divided by the time interval. If a frequency ratio counter is used, the acceleration amplitude a, expressed in m/s*, is calculated by the following formula: 4 = R, × 3. 123 × 10 -m
Sensitivity (amplitude) S, expressed in V/(ms-), is calculated by the following formula: s
Where:
X 0. 320 2 X 10°m -I
（4）
（5）
The ratio of the interference fringe frequency f, to the vibration frequency f, over a sufficient number of vibration cycles (depending on the grip frequency, for example at least 100 vibration cycles at 160 Hz). The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9 Method 2: Minimum point method
9.1 General
This method is applicable to the calibration of the sensitivity amplitude of accelerometers in the frequency range of 800 F-Iz to 10 k[z. The method described in this clause uses the white displacement corresponding to the point of the first-order Bessel function of the first kind to determine the displacement (see B.2 in Appendix B). The equivalent method of using the value of the independent variable corresponding to the zero point of the first-order Bessel function of the first kind can also be used to determine the displacement. However, the latter requires the modulation of the reference mirror (see reference [5]).
9.2 Measurement procedure
The output signal of the photoelectric receiver (4.6) is filtered with a bandpass filter (4.8) whose center frequency is equal to the vibration table frequency. The signal obtained after filtering contains a series of minimum points of the accelerometer displacement amplitude, see Table 1. Set the calibration frequency and then adjust the vibration table amplitude from zero so that the filtered photoelectric detection signal reaches a maximum value and then returns to a minimum value. This minimum value is the first minimum point. The amplitude corresponding to this point is 0.1930 μm. The amplitudes corresponding to other minimum points can be found in Table 1. The measurement system of the minimum point method is shown in Figure 2. Note 1: The first-order zero-order Hcsscl function can also be used to determine the acceleration sensitivity. In this case, the reference mirror is excited with a frequency lower than the reference frequency, and the center frequency of the bandpass filter or frequency analyzer is adjusted to the excitation frequency of the reference mirror (see reference [6]). Note 2: The modulation of the reference mirror position can also be used to improve the efficiency of the first-order Bess minimum point method (see reference [7]). Table 1 Displacement amplitude corresponding to the small point (1 = 0.63281μm) Smallest point
Displacement amplitude 3/
Smallest point
Amplitude/
Smallest point
Displacement amplitude 5/
2, 570 4
2. 728 64
Table 1 (continued)
GB/T 20485. 11—2006/ISO 16063-11: 1999 Smallest point
The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9.3 Expression of measurement results
See also B.2 in Closed Note B.
1—frequency generator (4.2);
-power amplifier (4.3)
vibration table (4.3);
—moving part of the vibration table:
5—mold disk block:
—frequency analyzer;
—amplifier:
-interferometer (4.6)1
9—laser (4.5),
photoelectric receiver:
frequency analyzer (4.8);
displacement amplitude 3/
—bandpass filter tunable according to vibration frequency (4.8)12
—voltmeter:
voltmeter (4,10)
15—distortion meter (4. 11),
oscilloscope (4.12).
Figure 2 Minimum point method (method 2) Tidal volume system
GB/T20485.11—2006/IS016063-11:1999 Acceleration amplitude t, expressed in m/s, is calculated by the following formula: 2 = 39, 478 X 3F2
Sensitivity (V/m·s-\) is expressed by the following formula: S = 0. 025 33 X
In the formula;
-amplitude of the output voltage of the accelerometer:
-displacement amplitude corresponding to each minimum point in Table 1; frequency of the vibration table.
10 Method 3: Sine approximation method
10.1 General
This method is applicable to the calibration of the sensitivity amplitude and (or) phase shift of accelerometers with a frequency range of 1 Hz to 10 kHz. 10.2 Measurement steps
Install the alarm according to Figures 3 and 4
(7)
Adjust the laser interferometer (Figure 4, for example) so that its output is two phase-orthogonal signals 2 and uz, and its tolerance meets the requirements of 4.6. After adjusting the interferometer (4.) to the best working state, measure the sensitivity amplitude and phase shift of the accelerometer according to the following steps under the specified vibration frequency and spherical amplitude (see Chapter 6). 1-Frequency generator (4.2):
2-Power amplifier (4.3);
Moving table (4.3)
Moving part of the vibration table 1
Analog mass block:
Accelerometer
Amplifier:
Interferometer (4.6):
Laser (4.5):
Photoelectric inspector:
Digital waveform recorder (4.13):
-Voltmeter (4.10);
Insulator (4.11);
Indicator (4.12).
Figure 3 Sine approximation method (Method 3 Measurement system GB/T20485.11-2006/[S0 16063-11:1999 Sinusoidal vibrations are applied to the accelerometer. The displacement amplitude should be large enough to produce at least one complete light and dark fringe in the interferometer output.
Go to 1: When the displacement value is not greater than 0.5 μm, the orthogonal output signal that meets the tolerance specified in 4.6 contains a variety of interference factors, the combined effect of which may cause the maximum error in the sensitivity value to be not less than 0.3% and the maximum error in the phase shift to be not less than 0.3°. This error can be reduced by adjusting to a tighter tolerance than 4.6 [see reference [8] or by using the correction procedure provided in reference []. Note 2: In order to achieve accurate measurement of the complex sensitivity and phase of the accelerometer within the nanometer displacement vibration range, the sinusoidal approach can be combined with a suitable heterodyne technique, see references [10_ and [11]. It can be calibrated off-frequency (e.g. 20 kHz).
Note 3: If the sinusoidal approximation method adopted by the frame has met the uncertainty requirements of Chapter 3, in order to improve the suppression efficiency of the quotient procedure, the position value or phase modulation value can be added and separated [12]-
Reference mirror
Vibration self-motion part:
3——Acceleration
1—-Simulation mass+
5-Beam splitter;
10.3Data acquisition
6.Polarizer;
-Optician;
8——Wolston prism:
9——Photoelectric receiver.
Figure 4 Orthogonal laser interferometer
The cutoff frequencies of the low-pass filter and the high-pass filter (if used) should be set to keep the interference of the low-pass filter on the calibration results within the tolerance range (see reference [). To satisfy the Naytsenter law, the sampling rate should be set so that the highest frequency is less than 1/2 of the sampling rate.
The analog-to-digital conversion of the accelerometer output voltage signal can be completed at the same or lower sampling rate as the analog-to-digital conversion rate of the interferometer output signal. The sampling of the three signals should start and end at the same time, and at least two of the output signals of the lower instrument should be synchronized with the same system clock.
should be sampled at tThe ratio of the interference fringe frequency f, to the vibration frequency. The calculation of the expanded measurement uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9 Method 2: Minimum point method
9.1 General
This method is applicable to the calibration of the sensitivity amplitude of accelerometers in the frequency range of 800F-Iz to 10k[z. The method described in this clause uses the displacement corresponding to the point of the first-order Bessel function of the first kind to determine the displacement (see B, 2 in Appendix B). The equivalent method of using the independent variable corresponding to the zero point of the first-order Bessel function of the first kind can also be used to determine the displacement. However, the latter requires the modulation of the reference lens (see reference [5]).
9.2 Measurement procedure
The output signal of the photoelectric receiver (4.6) is filtered with a bandpass filter (4.8) whose center frequency is equal to the vibration table frequency. The signal obtained after filtering contains a series of minimum points of the accelerometer displacement amplitude, see Table 1. Set the calibration frequency, and then adjust the vibration table amplitude from zero, so that the filtered photoelectric detection signal reaches a maximum value and then returns to a minimum value. This minimum value is the first minimum point. The amplitude corresponding to this point is 0.1930μm. The amplitudes corresponding to other minimum points can be found in Table 1. The measurement system of the minimum point method is shown in Figure 2. Note 1: The first-order zero-order Hcsscl function can also be used to determine the acceleration sensitivity. In this case, a reference mirror should be excited with a frequency lower than the reference frequency, and the center frequency of the bandpass filter or frequency analyzer should be adjusted to the excitation frequency of the reference mirror (see reference [6]). Note 2: The modulation of the reference mirror position can also be used to improve the efficiency of the first-order Bess minimum point method (see reference [7]). Table 1 Displacement amplitude corresponding to the small point (1 = 0.63281μm) Smallest point
Displacement amplitude 3/
Smallest point
Amplitude/
Smallest point
Displacement amplitude 5/
2, 570 4
2. 728 64
Table 1 (continued)
GB/T 20485. 11—2006/ISO 16063-11: 1999 Smallest point
The calculation of the measurement expanded uncertainty in the calibration result report shall comply with the requirements of Appendix A. 9.3 Expression of measurement results
See also B.2 in Closed Note B.
1—frequency generator (4.2);
-power amplifier (4.3)
vibration table (4.3);
—moving part of the vibration table:
5—mold disk block:
—frequency analyzer;
—amplifier:
-interferometer (4.6)1
9—laser (4.5),
photoelectric receiver:
frequency analyzer (4.8);
displacement amplitude 3/
—bandpass filter tunable according to vibration frequency (4.8)12
—voltmeter:
voltmeter (4,10)
15—distortion meter (4. 11),
oscilloscope (4.12).
Figure 2 Minimum point method (method 2) Tidal volume system
GB/T20485.11—2006/IS016063-11:1999 Acceleration amplitude t, expressed in m/s, is calculated by the following formula: 2 = 39, 478 X 3F2
Sensitivity (V/m·s-\) is expressed by the following formula: S = 0. 025 33 X
In the formula;
-amplitude of the output voltage of the accelerometer:
-displacement amplitude corresponding to each minimum point in Table 1; frequency of the vibration table.
10 Method 3: Sine approximation method
10.1 General
This method is applicable to the calibration of the sensitivity amplitude and (or) phase shift of accelerometers with a frequency range of 1 Hz to 10 kHz. 10.2 Measurement steps
Install the alarm according to Figures 3 and 4
(7)
Adjust the laser interferometer (Figure 4, for example) so that its output is two phase-orthogonal signals 2 and uz, and its tolerance meets the requirements of 4.6. After adjusting the interferometer (4.) to the best working state, measure the sensitivity amplitude and phase shift of the accelerometer according to the following steps under the specified vibration frequency and spherical amplitude (see Chapter 6). 1-Frequency generator (4.2):
2-Power amplifier (4.3);
Moving table (4.3)
Moving part of the vibration table 1
Analog mass block:
Accelerometer
Amplifier:
Interferometer (4.6):
Laser (4.5):
Photoelectric inspector:
Digital waveform recorder (4.13):
-Voltmeter (4.10);
Insulator (4.11);
Indicator (4.12).
Figure 3 Sine approximation method (Method 3 Measurement system GB/T20485.11-2006/[S0 16063-11:1999 Sinusoidal vibrations are applied to the accelerometer. The displacement amplitude should be large enough to produce at least one complete light and dark fringe in the interferometer output.
Go to 1: When the displacement value is not greater than 0.5 μm, the orthogonal output signal that meets the tolerance specified in 4.6 contains a variety of interference factors, the combined effect of which may cause the maximum error in the sensitivity value to be not less than 0.3% and the maximum error in the phase shift to be not less than 0.3°. This error can be reduced by adjusting to a tighter tolerance than 4.6 [see reference [8] or by using the correction procedure provided in reference []. Note 2: In order to achieve accurate measurement of the complex sensitivity and phase of the accelerometer within the nanometer displacement vib
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