Methods for the calibration of vibration and shock pick－ups－Primary vibration calibration by laser interferometry
Some standard content:
National Standard of the People's Republic of China
Calibration methods for vibration and shock sensors
Absolute vibration calibration by laser interferometry (primary calibration) Methods for the catibration of vibration and shock plck-ups Primary vlbration calihration by laser interferometry Subject content and scope of application
GR/T 13823.2—92
This standard specifies the calibration equipment, methods and data processing used when calibrating accelerometers by laser interferometry. This standard is mainly applicable to piezoelectric accelerometers, with a frequency range of 20~5000Hz and a dynamic range of 10~1000m/g2 Reference standards
GB/T13823.1 Calibration sheet method for vibration and shock sensors Basic concepts 3 Equipment
3.1 Environmental conditions
Calibration should be carried out under the following conditions:
Room: 20~5℃,
Relative sensitivity: less than 75%.
3.2 Technical requirements for instruments and equipment
The equipment block diagram is shown in Figures 1 and 2.
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Characteristic calibration meter
Method recovery
Spectral tower
Amplifier
Power amplifier
Figure 1 Frequency ratio counting method salt measurement system (Method 1) State Technical Supervision Bureau 1992-11-05 approved frequency ratio counting number|| tt||Amount rate north
Distortion meter
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1993-10-01 implementation
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: Loss height meter
AC excited digital voltmeter
3.2.1 Signal generator
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Variable inductance
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GB/T 13B23.2—92
Photodetector
Battery tri
Spectrophotometer
Operational
Method
Periodic rate sensor
Function
Figure 2 Bessel function zero value method measurement system (method 2) Frequency accuracy: The maximum limit error is 10.01% of the reading; Frequency stability: During the entire measurement period, it is better than 0.01% of the reading; Amplitude stability: During the entire measurement period, it is better than 10.01% of the reading. The output waveform (sine wave) has a point error of no less than 0.1. 3.2.2 Vibration generator
Acceleration waveform accuracy at the center of the table: no more than 2 s. Transverse vibration: less than 10% of the maximum acceleration in the main vibration direction at a frequency of 20-1000Hz; less than 20% of the maximum velocity in the main vibration direction at a frequency of more than 1000H. AC noise: at least 60dB lower than full output. Acceleration amplitude stability: better than the reading during measurement, 1. The base strain caused by the accelerometer mounting surface shall not affect the sensitivity. 3.2.3 The foundation (same foundation) used for the combination of vibration generator and laser interferometer shall be at least 2000 times the mass of the moving part of the vibration generator, the fixture and the accelerometer in the press. If there is the influence of pool surface vibration, a low-damping elastic suspension foundation shall be used, and the horizontal and vertical suspension resonant frequencies shall be between 1~~2Hz. 3-2.4 The wavelength of the amine laser is 0. (32 8μm. 3.2.5 The inverse Kelson interferometer with a photodetector should have a DC to 15MHz response. 3.2.6 Counter
Frequency range: 10 to 2×10°Hz;
Accuracy: The maximum limit error is 0.01% of the reading. 3.2.7 Adjustable latent filter or spectrum analyzer Frequency range: 100~1×10°Hz;
Width: at least 12% of the center frequency;
Filter material rate: excellent 24lB/0 CT:
Customer standard industry data free download Signal-to-noise ratio: at least 70dB lower than full output, dynamic range: better than 6CdB.
3.2.8 Digital voltmeter (true RMS)
Frequency range: 20~5000Hz;
CB/T 13823.2—92
Accuracy, the maximum limit error is ±0.01% of the reading, 0.1% at 40Hz. 3.2.9 Distortion measuring instrument
Distortion measurement range: 0~5%
Frequency range: 5Hz～10kHz t
Accuracy, the maximum limit error is ±10% of the reading. 3.2.10 Indicator: used to check the waveform of the accelerometer output signal. Frequency range: 5~5 000Hz,
3.2.11 Other requirements
To achieve the accuracy requirement of 0.5%, the calibrated accelerometer and its amplifier should be considered as a whole and calibrated together. The structure of the calibrated accelerometer must be rigid, and the base strain sensitivity should not be greater than 0.003m·5-2/E. The maximum lateral sensitivity ratio is 2%. The annual stability of the reference sensitivity of the calibrated accelerometer and its amplifier combination should be better than 1% of the reading. 4 Preferred amplitudes and frequencies
Six amplitudes and six frequencies that cover the working range of the accelerometer are selected from the following system: acceleration (instrument used for method 1), 10, 20, 50100, 500m/s2; reference acceleration 100m/s (the first choice is 10m/s) frequency: 20.40, 80, 160, 315.630.1 250.2500, 5 000Hz reference frequency, 160Hz (second choice is 80Hz). 5 Error range
When the reference frequency is 160Hz (second choice is 80Hz), the reference amplitude is 100m/s (second choice is 1(hm/s=) and the amplification is at the set gain position, it is ±0.5% of the reading, when the frequency rises to 1000Hz, it is ±1% of the reading, and when the frequency exceeds 1000Hz, it is ±2% of the setting.
6 Method 1 Frequency ratio counting method
6.1 Applicable frequency range: 20～1250Hz. 6.2 Measurement steps
6.2. 1 According to Figure 1 Connect the calibration system. 6.2.2 After adjusting the interferometer to the best state, select the frequency of 160Hz (the first choice is 80Hz), the acceleration amplitude of 10m/ (the first choice is 10m/\), the amplifier gain is at the set position, use the frequency ratio counter to measure the ratio of the plate fringe frequency to the plate vibration frequency, and read the accelerometer output voltage value from the digital voltmeter, and calculate the reference sensitivity of the accelerometer according to formula (2). 6.2.3 Determine the sensitivity of the accelerometer by selecting the amplitude and frequency according to Chapter 4, and give the percentage deviation from the reference sensitivity. 6.2.4 The table distortion, lateral and noise shall be measured for each frequency and acceleration combination, and the test results shall meet the requirements specified in Article 3.2.2.
6.2.5 Calibration results and data processing
Calculate the acceleration amplitude α from the number of interference fringes displayed by the frequency ratio counter: a = 3.122 8 × 10-s × f2 XR, (m/s\) Sensitivity S.
CB/T 13823. 2—92
S = 4. 528 7 × 105
Where: E——accelerometer output (single) amplitude voltage, mV (effective value); f is the vibration frequency, H2;
T——vibration period + s;
R. The ratio of the interference fringe frequency to the vibration frequency under optical and electrical conduction (mV/(m--°))
In the high frequency band, in order to improve the calibration accuracy, the multi-cycle averaging method should be used to measure the amplitude, and the cycle should be at least 100. Repeat the above steps 10 times and take the average value as the sensitivity value at the problem point. (2)
When reporting the calibration results, the total uncertainty of the calibration and the corresponding confidence level should be calculated according to Appendix A, and a confidence level of 99% should be used (the second option is a confidence level of 95%).
7 Method 2 Bessel function zero value method
7.1 Applicable frequency range: 1250~5×10Hz, 7.2 Measurement steps
7.2.1 Connect the Bessel function zero value method measurement system according to Figure 2. 7.2.2 The signal from the photodetector passes through the frequency analyzer and uses the zero value method or the zero value method to detect the amplitude. Their measurement steps are as follows:
a, J, in the zero value method, the center frequency of the frequency analyzer is synchronized with the vibration frequency of the vibration generator, the vibration generator is turned on and the vibration value is gradually increased, so that the photoelectric signal reaches the first maximum value. At this time, the vibration displacement of the vibration generator is 0.0927am). Adjust the DC supply voltage of the piezoelectric stack so that the indication of the frequency analyzer reaches the maximum value V1. Then increase the vibration amplitude of the table so that the photoelectric signal indicated by the frequency analyzer reaches the first minimum value V2. At this time, the vibration displacement of the vibration generator is 0.1930um (at this time V./V, should be less than -60dB). Repeat ten times and take the average value. Corresponding to other value points, the corresponding displacement values can be found from the table (J, displacement amplitude corresponding to the zero value method). It should be noted that when the vibration value of the vibration generator is reduced to 0.0927um, the frequency analyzer should still indicate the value of V. If the difference is too large, the measurement should be renewed. Table 1J, corresponding displacement amplitude
zero point
displacement amplitude dm
.J. In the zero value method, the center frequency of the frequency analyzer is synchronized with the vibration frequency of the reference reflector (250Hz), and the vibration value of the reference reflector is adjusted so that the photoelectric signal reaches the first maximum value. At this time, the vibration displacement of the reference reflector is 0.0927um. Adjust the DC supply voltage of the piezoelectric stack so that the photoelectric signal reaches the maximum value, and record the voltage value V. Then turn on the vibration generator system and increase the resonance vibration value so that the photoelectric signal reaches the first minimum value V. At this time, the vibration displacement of the vibration generator is 0.1211μm (at this time, V/V should be less than -60dB). Repeat ten times and take the average value. The corresponding displacement values corresponding to other minimum points can be found from Table 2 (J, corresponding displacement amplitude of zero value method). It should be noted that after turning off the vibration generator system, the value indicated by the frequency analyzer should still be V, if it changes greatly, the measurement should be invalidated and the above measurement should be repeated
Zero point
Displacement amplitude d,μrm0.000 0
0121 1
7.2-3 Calibration results and data processing
GB/T 13823. 2-92
Table 2J. Zero value method corresponding displacement amplitude
According to the measured vibration displacement (0.1930μm or 0.1211μm) and vibration rate, calculate the acceleration: a - 39. 478 × 10-f × d × f2 (m/s*)7
According to the acceleration, measure the output voltage E of the calibrated accelerometer and calculate the sensitivity of the calibrated accelerometer: 5 = 0. 358 17 ×10°7×
In the formula: a - accelerometer output (single) amplitude voltage, mV (effective value) d
- displacement amplitude: 1, according to Table 1 or Table 2,
f vibration rate, Hz.
(mV/(mst))
Repeat the above steps 10 times, and use the average value of 10 times as the sensitivity at this frequency point. By changing the frequency and repeating the above steps, the sensitivity of the calibrated accelerometer at other frequency points can be obtained. According to the sensitivity at different frequencies measured, calculate the percentage deviation of the sensitivity measured at 160Hz (or 80Hz) and 100m/s (or 10m/s) according to method 1 (see Chapter 6). When reporting the calibration results, the total uncertainty of the calibration and the corresponding confidence level shall be calculated according to Appendix A. The 99% confidence level should be used (the first choice is 95% confidence level). Calculation of total uncertainty GB/T 13823. 2-92 Appendix A Calculation of uncertainty (supplement) The total uncertainty of calibration under the specified confidence level: CL = 99% or 95% + X should be calculated as follows: Xer ± Vx + x? Where: X, - random uncertainty; X - systematic uncertainty. For the random uncertainty X of the specified confidence level,The instrument is valid for the calibration frequency, amplitude and amplifier at the set gain position. The total absolute difference (es) in sensitivity (mV/(m·s\)) and the uncertainty in the entire frequency and amplitude range are calculated as follows:
(+(+(+(+()+(+++
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Where: 5——sensitivity, V/(mg*) (see 6.2 or 7.2); s--absolute error in sensitivity (mV/m·s2) calculated according to A2.1 or A2.2 at the reference frequency, amplitude and amplifier at the set gain position;
frequency linearity deviation of the reference amplifier, expressed as a percentage of the reference calibration factor; I.tA
Lir—Frequency linear deviation of reference accelerometer, expressed as a percentage of reference sensitivity; L—Amplitude linear deviation of reference amplifier, expressed as a percentage of reference calibration coefficient; Lp—Amplitude linear deviation of reference accelerometer, expressed as a percentage of reference sensitivity; I.—Instability of reference amplifier gain and source impedance error, expressed as a percentage of reference calibration coefficient; R—Tracking error of reference amplifier base (error of different amplifier gain positions), expressed as a percentage of reference calibration coefficient;
F—Error of reference amplifier caused by environmental influence, expressed as a percentage of reference calibration coefficient;
F—Error of reference accelerometer caused by environmental influence, expressed as a percentage of reference sensitivity. Additional remarks:
This standard is proposed and managed by the National Technical Committee for Mechanical Moving and Impact Standardization. This standard is drafted by the China National Institute of Metrology. The main drafters of this standard are Xia Huiying, Yang Suzhen, and Gao Jinfang.
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