Some standard content:
GB/T17251—1998
The hydrophone acceleration sensitivity measurement method has been used in my country's industrial and scientific research departments for many years. In order to unify the measurement method and ensure the uniformity and accuracy of the measured value, this standard is specially formulated. Appendix A of this standard is a suggestive appendix. This standard is proposed and managed by the National Technical Committee for Acoustics Standardization. The drafting units of this standard are: the 715th Institute of China State Shipbuilding Corporation and the Institute of Acoustics of the Chinese Academy of Sciences. The main drafters of this standard are: Xue Yaoquan, Zhu Yuanqing, Shuai Wenjun, and Shen Jianxin. 1 Scope
National Standard of the People's Republic of China
Acoustics--.Calibration method of hydrophoneacceleration sensitivity
This standard specifies the measurement method of hydrophone acceleration sensitivity. GB/T 17251—1998
The applicable measurement frequency range of this standard is 10~2000Hz, and the acceleration value range is 1~100m/s. 2 Reference standards
The clauses contained in the following standards constitute the clauses of this standard through reference in this standard. When this standard is released, the versions shown are valid. All standards will be revised. All parties using this standard should explore the possibility of using the latest versions of the following standards. GB3240-82 Commonly used rates in acoustic measurement GB3/T3947-1996 Acoustic terminology
3 Definitions
This standard adopts the following definitions:
acceleration sensitivity of hydrophone3.1 Velocity sensitivity of hydrophone
The ratio of the open circuit voltage U of a hydrophone that is accelerating in a certain direction to the upward acceleration a of the force. The unit is volt·second squared per meter, Vs'/m.
Expressed by formula (1):
M. = U,/a
3.2 Acceleration sensitivity level of hydrophone (1)
The logarithm of the ratio of the hydrophone acceleration sensitivity value M. to the reference sensitivity M. multiplied by 20, in decibels, dB, is expressed by formula (2):
Mr = 20lg(M./M)
Note: The reference sensitivity is generally 1V·a/m. In case of explanation, it can also be taken as 1/9.80V·/m. 4 Calibration
4.1. Methods for calibrating the acceleration sensitivity of a hydrophone2
By definition, when calibrating the acceleration sensitivity of a hydrophone, there are two independent quantities to be measured at a given frequency, one is the vibration acceleration to which the hydrophone is subjected, and the other is its open-circuit output voltage when it is subjected to vibration. There are two methods for measuring the perturbation acceleration of a mouse: one is to use a general piezoelectric accelerometer, and the other is to use a laser vibrometer. 4.1.1 Standard accelerometer method
The perturbation acceleration of the calibrated hydrophone can be given by the standard accelerometer on the vibration table. The acceleration sensitivity of the calibrated hydrophone is:
GB/T17251—1998
M, = 20lg
+ 20lgM - 20lgM.
Wu Zhong: U.-Output voltage of the standard accelerometer amplifier, V#M——Voltage sensitivity of the standard accelerometer (including the accelerometer amplifier amplification), V·s/m; AM.r
-Base sensitivity, Vs\/m.
The recommended calibration equipment connection diagram is shown in Figure 1. The calibrated hydrophone and the standard accelerometer are rigidly fixed on the table of the vibration table at the same time so that they are subjected to the same acceleration. When the vibration table is subjected to a certain frequency vibration acceleration, the output voltage of the preamplifier is first measured, and then the open circuit voltage of the hydrophone to be calibrated is measured. If the hydrophone to be calibrated has a high output impedance, its output terminal must be connected to a preamplifier with a higher input impedance for impedance conversion. Finally, the measurement result is calculated by using formula (3) or (4). Charge effector
Presenter
Standard accelerometer
Power amplifier
With ripple filter
Avoidance effector
Rate synthesizer
Digital voltage analyzer
Figure 1. Acceleration sensitivity of hydrophone calibrated with standard accelerometer. Figure 4.1.2. Laser vibrometer
When the vibration acceleration to which the hydrophone is subjected is directly measured with a laser vibrometer, the acceleration sensitivity of the hydrophone to be calibrated can be directly calculated using formula (1). The recommended calibration block diagram is shown in Figure 2. The hydrophone to be calibrated is rigidly fixed on the vibration table, the optical probe focus is selected at a certain point on the top of the hydrophone to be measured, and the laser vibrometer directly measures the vibration acceleration of the hydrophone. If the hydrophone to be calibrated has a high output impedance, its output must be connected to a preamplifier with a higher input impedance for impedance conversion, and then input to the measurement amplifier.
Laser probe
Vibration table
Light source
Amplifier
Oscilloscope
Power amplifier
Filter
Measurement amplifier
Digital voltmeter
Synthesizer
Instrument controller
External equipment
4.2 Calibration signal and frequency
G/T 17251—1998
Sine signal is recommended as the calibration signal. Within the use range, the frequency should adopt the frequency specified in the frequency series of GB3240. In general, the frequency adopts the central frequency of 1/3 frequency. If necessary, the measurement frequency interval can also be adjusted according to the needs. The frequency uncertainty is required to be less than 0.2%. 4.3 Calibration equipment and environmental requirements
4.3.1 Vibration table
The vibration table is a vibration source that produces stable sinusoidal vibration. During calibration, the accelerometer and the hydrophone to be calibrated are rigidly mounted on its table top at the same time. Generally, the frequency range of the perturbation table is required to be 10~20001z, and the acceleration range is 1~100m/s*. The nonlinear distortion of the vibration is required to be less than 1%, and the instability is required to be less than 0.5% per hour. The table top of the vibration table must have sufficient rigidity and thickness to avoid bending or resonance of the table top within the frequency range of use, resulting in waveform distortion or instability. It is also required that the vibration table surface is straight, and the speed and water device can be reliably connected to the table. The vibration table should maintain vertical vibration, and the lateral vibration component should be less than 3%. 4.3.2 Standards for accelerometers
a) The sensitivity of the accelerometer must be calibrated and used within the qualified period, and its standard uncertainty is less than 3%; b) The ratio of the lateral sensitivity to the longitudinal sensitivity shall not be greater than 3%; c) The nonlinear distortion of the accelerometer within the required frequency range is less than 1%; d) The influence of the non-vibration environmental sensitivity of the accelerometer should be less than -30 dB. Method: The accelerometer is an electromechanical converter, which should only respond to acceleration and not to other physical quantities. However, due to the sensor structure and the characteristics of the sensor element to multiple physical quantities, the sensor is also affected by other physical quantities when measuring the physical quantity, such as the influence of the electric field, the influence of the temperature field or the influence of the environmental noise field, etc. This sensitivity to other physical quantities in addition to the response to acceleration is collectively referred to as its non-vibration environmental sensitivity.
4.3.3 Laser vibrometer
The laser vibrometer is a non-contact vibration sensor. It is not necessary to install a reflector, a reflector or any other reflective coating on the calibrated hydrophone, thus completely avoiding the influence of the additional mass on the calibrated hydrophone. The laser vibrometer outputs a concentrated beam on the surface of the acceleration direction of the calibrated hydrophone. The speed decoder in the laser vibrometer can directly output the vibration acceleration of the calibrated hydrophone. The laser vibrometer should meet the following conditions: a) The laser vibrometer must be calibrated and used within the qualified period, and its calibration uncertainty is less than 1%; b) The nonlinear distortion of the laser vibrometer in the dynamic range of the frequency range required by this standard is less than 0.5%; c) The maximum measurement distance of the laser vibrometer is greater than 0.3m. 4.4 Discharger, voltmeter and filter
The output impedance of the standard accelerometer is very high, and a charge amplifier is generally used as its preamplifier. The output voltage of the charge amplifier can be read directly by a digital voltmeter, and can also be read after being amplified by a measuring amplifier if necessary. The measurement uncertainty of the voltmeter should be less than 0.1 dB.
The open circuit voltage of the measured hydrophone can also be read by the voltmeter after being discharged by the measuring amplifier. The input impedance of the measuring amplifier is required to be at least 100 times higher than the impedance of the hydrophone (the voltage coupling loss introduced by this will be less than 0.1 dB).If the input impedance of the amplifier does not meet the above requirements, it is necessary to use a pre-amplifier with high input impedance to perform impedance conversion in advance. In order to improve the measurement signal-to-noise ratio, especially to ensure sufficient signal-to-noise ratio when measuring hydrophones with very low acceleration sensitivity, the amplifier needs to be equipped with a bandpass filter group, or a phase-locked amplifier or an external amplifier that uses the vibration excitation signal as the reference signal. 4.3.5 Laboratory environmental conditions
) The laboratory temperature should be controlled within the normal working range of the measuring equipment and hydrophone. There should be no heat source on or around the vibration table to avoid the temperature gradient bottle in the room causing the ambient temperature change and affecting the measurement accuracy;
4.4 Installation of accelerometer and calibrated hydrophone GB/T 17251—1998
When using the accelerometer vibration measurement method, the standard accelerometer and the calibrated hydrophone must be installed on the vibration table at the same time. In order to ensure the accuracy of the acceleration measurement of the calibrated hydrophone, they are placed as shown in Figure 1. An accelerometer is installed on each side of the calibrated hydrophone to monitor the vibration acceleration of the table surface at the same time. If the vibration of the vibration table is stable, the vibration distribution of the table surface is uniform, and the installation of the calibrated hydrophone does not affect the vibration distribution of the vibration table surface, then an accelerometer can also be used. 4.4.1 Installation of piezoelectric accelerometer
The following two installation methods can be used:
Moving table
Vibrating table
Figure 3 Schematic diagram of piezoelectric accelerometer installation
a) Steel column bolt connection method: The piezoelectric accelerometer is tightened on the vibration table with steel column bolts as shown in Figure 3 (). If the installation surface is not smooth enough, a thin layer of silicone tire is applied to the bottom before screwing on the piezoelectric accelerometer. If the table is charged, it is required to use an insulating sheet (such as mica sheet) as a gasket and then tighten it with steel as an insulating bolt: b) Permanent iron connection method: The positive accelerometer is connected to the permanent magnet with a steel column bolt, and then the permanent magnet is adsorbed on the vibration table, as shown in Figure 3 (b). When using this connection method, the vibration table surface must be made of metal materials that are attracted to magnets, such as steel. Regardless of the above installation, it must be ensured that the accelerometer axis is perpendicular to the vibration table surface. 4.4.2 Installation of the calibrated hydrophone
) The calibrated hydrophone is fixed to the table of the gripping table by a specially designed fixture. The structure and holding method of the fixture must ensure that the response of the hydrophone to acceleration is not changed and the acceleration of the table vibration potential is transmitted to the hydrophone without attenuation: 6) The acceleration at the installation position of the calibrated hydrophone must be equal to the acceleration value at the point where the standard accelerometer is located. 5 Calibration uncertainty
The uncertainty of the calibration of the hydrophone acceleration sensitivity is a combination of the uncertainty component caused by random effects (referred to as type A components) and the uncertainty component caused by system effects (referred to as type B components). When the calibration conditions meet the requirements of this standard, the type B uncertainty component is less than 0.6dB. GB/T17251—1998
Appendix 4
(Suggested Appendix)
Analysis of uncertainty of calibration results
The uncertainty of the calibration result reflects the insufficient understanding of the calibrated value. The calibration result after correction for the known system effects is still an estimate of the calibrated value, because there are still uncertainties caused by random effects and uncertainties introduced by incomplete correction of system effects.
The uncertainty component caused by random effects is called Class A standard uncertainty component (referred to as Class A component), and the uncertainty component introduced by incomplete correction of system effects is called Class B standard uncertainty component (referred to as Class B component). A1 Class A standard uncertainty component
Class A standard uncertainty component is evaluated by statistical analysis method and expressed by standard deviation. If the calibration result of hydrophone acceleration sensitivity is expressed by single calibration value, and the A component is expressed by experimental standard deviation S of calibration device, its estimation formula is: WA-S,
--++( Al )
If it is expressed by arithmetic mean of independent calibrations, and the A component is expressed by experimental standard deviation of half mean, its estimation formula is:
wa =S,-S/ Vn
Where: M.———acceleration sensitivity of independent calibration V-/m: M--arithmetic mean value of acceleration sensitivity of multiple independent calibrations, V·s*/m; Fill—number of independent calibrations.
It can be seen that the experimental standard deviation of arithmetic mean of limited calibrations is inversely proportional to \: as the number of calibrations increases, the dispersion of arithmetic mean decreases, but when >20, S, decreases slowly, and the increase of calibration times means the increase of calibration time and cost, so... * In general, n is between 4 and 20 times, and this standard recommends =6. A2B type standard uncertainty components
In the hydrophone acceleration sensitivity calibration, the B type standard uncertainty components mainly include the following influence quantities: a) The uncertainty of the calibration value of the standard accelerometer. If the uncertainty is 7.5% at the confidence level of 99% (-3), then its B type standard uncertainty is:
#B-2.5%
b) This standard allows the ratio of the lateral to longitudinal sensitivity of the standard accelerometer to be less than 3%, and the lateral distribution of the vibration table to be less than 3%. Therefore, the influence of the lateral component in the calibration result is 0.09% (confidence level 95%, Table 1-2), so: wB-0.045%
) The voltage measurement system in the calibration device is shared by the standard accelerometer and the hydrophone, so the influence it introduces must be doubled. The standard requires that the uncertainty of voltage is (confidence level 95%, = 2), so: u = 1.2%
d) This standard requires that the input impedance of the measuring amplifier is 100 times higher than the impedance of the hydrophone, so the voltage coupling loss can be introduced to be about 1.2%:
CB/T 17251-1998
) This standard requires that the signal frequency uncertainty is 0.5 (confidence level 95%, -2), then: MmEe - 0. 25%
Therefore, Class B component
: 3. 2% (0. 3 dB
13 Synthetic standard uncertainty
In the calibration of hydrophone acceleration sensitivity, the standard uncertainty of the calibration result includes Class A component and Class B component. Obviously, they are unrelated to each other. Therefore, the synthetic standard uncertainty is their square root value: u— Vu +
A4 Expanded uncertainty
The expanded uncertainty is expressed as U. Therefore, the calibration result of the hydrophone acceleration sensitivity can be expressed as M.-M, ±U
The combined uncertainty is multiplied by the included factor to obtain: Uk-uc
(A3)
-{A4）
-(A5)
The included value is selected according to the confidence level required for the interval of crown, second (!), generally within the range of 2 to 3 weeks, when table = 2, the interval setting level is about 95%, when a higher confidence level is required, it can be taken as = 3, at this time the confidence level is about 9%. This standard recommends starting from 2.1 Installation of piezoelectric accelerometer
The following two installation methods can be used:
Moving table
Vibrating table
Figure 3 Schematic diagram of piezoelectric accelerometer installation
a) Steel column bolt connection method: Tighten the piezoelectric accelerometer on the vibration table with steel column bolts as shown in Figure 3 (). If the installation surface is not smooth and flat, apply a thin layer of silicone tire on the bottom before screwing on the piezoelectric accelerometer. If the table is charged, it is required to use an insulating sheet (such as mica sheet) as a gasket and then tighten it with steel as an insulating bolt: b) Permanent iron connection method: Connect the positive accelerometer to the permanent magnet with steel column bolts, and then adsorb the permanent magnet on the vibration table, as shown in Figure 3 (b). When using this connection method, the vibration table must be made of metal materials that are attracted to magnets, such as steel. Regardless of the above installation, it must be ensured that the accelerometer axis is perpendicular to the vibration table. 4.4.2 Installation of the calibrated hydrophone
) The calibrated hydrophone is fixed to the table of the gripping table by a specially designed fixture. The structure and holding method of the fixture must ensure that the response of the hydrophone to acceleration is not changed and the acceleration of the table vibration potential is transmitted to the hydrophone without attenuation: 6) The acceleration at the installation position of the calibrated hydrophone must be equal to the acceleration value at the point where the standard accelerometer is located. 5 Calibration uncertainty
The uncertainty of the calibration of the hydrophone acceleration sensitivity is a combination of the uncertainty component caused by random effects (referred to as type A components) and the uncertainty component caused by system effects (referred to as type B components). When the calibration conditions meet the requirements of this standard, the type B uncertainty component is less than 0.6dB. GB/T17251—1998
Appendix 4
(Suggested Appendix)
Analysis of uncertainty of calibration results
The uncertainty of the calibration result reflects the insufficient understanding of the calibrated value. The calibration result after correction for the known system effects is still an estimate of the calibrated value, because there are still uncertainties caused by random effects and uncertainties introduced by incomplete correction of system effects.
The uncertainty component caused by random effects is called Class A standard uncertainty component (referred to as Class A component), and the uncertainty component introduced by incomplete correction of system effects is called Class B standard uncertainty component (referred to as Class B component). A1 Class A standard uncertainty component
Class A standard uncertainty component is evaluated by statistical analysis method and expressed by standard deviation. If the calibration result of hydrophone acceleration sensitivity is expressed by single calibration value, and the A component is expressed by experimental standard deviation S of calibration device, its estimation formula is: WA-S,
--++( Al )
If it is expressed by arithmetic mean of independent calibrations, and the A component is expressed by experimental standard deviation of half mean, its estimation formula is:
wa =S,-S/ Vn
Where: M.———acceleration sensitivity of independent calibration V-/m: M--arithmetic mean value of acceleration sensitivity of multiple independent calibrations, V·s*/m; Fill—number of independent calibrations.
It can be seen that the experimental standard deviation of arithmetic mean of limited calibrations is inversely proportional to \: as the number of calibrations increases, the dispersion of arithmetic mean decreases, but when >20, S, decreases slowly, and the increase of calibration times means the increase of calibration time and cost, so... * In general, n is between 4 and 20 times, and this standard recommends =6. A2B type standard uncertainty components
In the hydrophone acceleration sensitivity calibration, the B type standard uncertainty components mainly include the following influence quantities: a) The uncertainty of the calibration value of the standard accelerometer. If the uncertainty is 7.5% at the confidence level of 99% (-3), then its B type standard uncertainty is:
#B-2.5%
b) This standard allows the ratio of the lateral to longitudinal sensitivity of the standard accelerometer to be less than 3%, and the lateral distribution of the vibration table to be less than 3%. Therefore, the influence of the lateral component in the calibration result is 0.09% (confidence level 95%, Table 1-2), so: wB-0.045%
) The voltage measurement system in the calibration device is shared by the standard accelerometer and the hydrophone, so the influence it introduces must be doubled. The standard requires that the uncertainty of voltage is (confidence level 95%, = 2), so: u = 1.2%
d) This standard requires that the input impedance of the measuring amplifier is 100 times higher than the impedance of the hydrophone, so the voltage coupling loss can be introduced to be about 1.2%:
CB/T 17251-1998
) This standard requires that the signal frequency uncertainty is 0.5 (confidence level 95%, -2), then: MmEe - 0. 25%
Therefore, Class B component
: 3. 2% (0. 3 dB
13 Synthetic standard uncertainty
In the calibration of hydrophone acceleration sensitivity, the standard uncertainty of the calibration result includes Class A component and Class B component. Obviously, they are unrelated to each other. Therefore, the synthetic standard uncertainty is their square root value: u— Vu +
A4 Expanded uncertainty
The expanded uncertainty is expressed as U. Therefore, the calibration result of the hydrophone acceleration sensitivity can be expressed as M.-M, ±U
The combined uncertainty is multiplied by the included factor to obtain: Uk-uc
(A3)
-{A4）
-(A5)
The included value is selected according to the confidence level required for the interval of crown, second (!), generally within the range of 2 to 3 weeks, when table = 2, the interval setting level is about 95%, when a higher confidence level is required, it can be taken as = 3, at this time the confidence level is about 9%. This standard recommends starting from 2.1 Installation of piezoelectric accelerometer
The following two installation methods can be used:
Moving table
Vibrating table
Figure 3 Schematic diagram of piezoelectric accelerometer installation
a) Steel column bolt connection method: Tighten the piezoelectric accelerometer on the vibration table with steel column bolts as shown in Figure 3 (). If the installation surface is not smooth and flat, apply a thin layer of silicone tire on the bottom before screwing on the piezoelectric accelerometer. If the table is charged, it is required to use an insulating sheet (such as mica sheet) as a gasket and then tighten it with steel as an insulating bolt: b) Permanent iron connection method: Connect the positive accelerometer to the permanent magnet with steel column bolts, and then adsorb the permanent magnet on the vibration table, as shown in Figure 3 (b). When using this connection method, the vibration table must be made of metal materials that are attracted to magnets, such as steel. Regardless of the above installation, it must be ensured that the accelerometer axis is perpendicular to the vibration table. 4.4.2 Installation of the calibrated hydrophone
) The calibrated hydrophone is fixed to the table of the gripping table by a specially designed fixture. The structure and holding method of the fixture must ensure that the response of the hydrophone to acceleration is not changed and the acceleration of the table vibration potential is transmitted to the hydrophone without attenuation: 6) The acceleration at the installation position of the calibrated hydrophone must be equal to the acceleration value at the point where the standard accelerometer is located. 5 Calibration uncertainty
The uncertainty of the calibration of the hydrophone acceleration sensitivity is a combination of the uncertainty component caused by random effects (referred to as type A components) and the uncertainty component caused by system effects (referred to as type B components). When the calibration conditions meet the requirements of this standard, the type B uncertainty component is less than 0.6dB. GB/T17251—1998
Appendix 4
(Suggested Appendix)
Analysis of uncertainty of calibration results
The uncertainty of the calibration result reflects the insufficient understanding of the calibrated value. The calibration result after correction for the known system effects is still an estimate of the calibrated value, because there are still uncertainties caused by random effects and uncertainties introduced by incomplete correction of system effects.
The uncertainty component caused by random effects is called Class A standard uncertainty component (referred to as Class A component), and the uncertainty component introduced by incomplete correction of system effects is called Class B standard uncertainty component (referred to as Class B component). A1 Class A standard uncertainty component
Class A standard uncertainty component is evaluated by statistical analysis method and expressed by standard deviation. If the calibration result of hydrophone acceleration sensitivity is expressed by single calibration value, and the A component is expressed by experimental standard deviation S of calibration device, its estimation formula is: WA-S,
--++( Al )
If it is expressed by arithmetic mean of independent calibrations, and the A component is expressed by experimental standard deviation of half mean, its estimation formula is:
wa =S,-S/ Vn
Where: M.———acceleration sensitivity of independent calibration V-/m: M--arithmetic mean value of acceleration sensitivity of multiple independent calibrations, V·s*/m; Fill—number of independent calibrations.
It can be seen that the experimental standard deviation of arithmetic mean of limited calibrations is inversely proportional to \: as the number of calibrations increases, the dispersion of arithmetic mean decreases, but when >20, S, decreases slowly, and the increase of calibration times means the increase of calibration time and cost, so... * In general, n is between 4 and 20 times, and this standard recommends =6. A2B type standard uncertainty components
In the hydrophone acceleration sensitivity calibration, the B type standard uncertainty components mainly include the following influence quantities: a) The uncertainty of the calibration value of the standard accelerometer. If the uncertainty is 7.5% at the confidence level of 99% (-3), then its B type standard uncertainty is:
#B-2.5%
b) This standard allows the ratio of the lateral to longitudinal sensitivity of the standard accelerometer to be less than 3%, and the lateral distribution of the vibration table to be less than 3%. Therefore, the influence of the lateral component in the calibration result is 0.09% (confidence level 95%, Table 1-2), so: wB-0.045%
) The voltage measurement system in the calibration device is shared by the standard accelerometer and the hydrophone, so the influence it introduces must be doubled. The standard requires that the uncertainty of voltage is (confidence level 95%, = 2), so: u = 1.2%
d) This standard requires that the input impedance of the measuring amplifier is 100 times higher than the impedance of the hydrophone, so the voltage coupling loss can be introduced to be about 1.2%:
CB/T 17251-1998
) This standard requires that the signal frequency uncertainty is 0.5 (confidence level 95%, -2), then: MmEe - 0. 25%
Therefore, Class B component
: 3. 2% (0. 3 dB
13 Synthetic standard uncertainty
In the calibration of hydrophone acceleration sensitivity, the standard uncertainty of the calibration result includes Class A component and Class B component. Obviously, they are unrelated to each other. Therefore, the synthetic standard uncertainty is their square root value: u— Vu +
A4 Expanded uncertainty
The expanded uncertainty is expressed as U. Therefore, the calibration result of the hydrophone acceleration sensitivity can be expressed as M.-M, ±U
The combined uncertainty is multiplied by the included factor to obtain: Uk-uc
(A3)
-{A4）
-(A5)
The included value is selected according to the confidence level required for the interval of crown, second (!), generally within the range of 2 to 3 weeks, when table = 2, the interval setting level is about 95%, when a higher confidence level is required, it can be taken as = 3, at this time the confidence level is about 9%. This standard recommends starting from 2.5%
b) This standard allows the ratio of the lateral to longitudinal sensitivity of the standard accelerometer to be less than 3%, and the lateral component of the vibration table to be less than 3%. Therefore, the influence of the lateral component in the calibration result is 0.09% (confidence level 95%, Table 1-2), so: wB-0.045%
) The voltage measurement system in the calibration device is shared by the standard accelerometer and hydrophone, so the influence it introduces must be doubled. The standard requires that the uncertainty of voltage is (confidence level 95%, = 2), so: u = 1.2%
d) This standard requires that the input impedance of the measuring amplifier is 100 times higher than the impedance of the hydrophone, so the voltage coupling loss can be introduced to be about 1.2%:
CB/T 17251-1998
) This standard requires that the signal frequency uncertainty is 0.5 (confidence level 95%, -2), then: MmEe - 0. 25%
Therefore, Class B component
: 3. 2% (0. 3 dB
13 Synthetic standard uncertainty
In the calibration of hydrophone acceleration sensitivity, the standard uncertainty of the calibration result includes Class A component and Class B component. Obviously, they are unrelated to each other. Therefore, the synthetic standard uncertainty is their square root value: u— Vu +
A4 Expanded uncertainty
The expanded uncertainty is expressed as U. Therefore, the calibration result of the hydrophone acceleration sensitivity can be expressed as M.-M, ±U
The combined uncertainty is multiplied by the included factor to obtain: Uk-uc
(A3)
-{A4）
-(A5)
The included value is selected according to the confidence level required for the interval of crown, second (!), generally within the range of 2 to 3 weeks, when table = 2, the interval setting level is about 95%, when a higher confidence level is required, it can be taken as = 3, at this time the confidence level is about 9%. This standard recommends starting from 2.5%
b) This standard allows the ratio of the lateral to longitudinal sensitivity of the standard accelerometer to be less than 3%, and the lateral component of the vibration table to be less than 3%. Therefore, the influence of the lateral component in the calibration result is 0.09% (confidence level 95%, Table 1-2), so: wB-0.045%
) The voltage measurement system in the calibration device is shared by the standard accelerometer and hydrophone, so the influence it introduces must be doubled. The standard requires that the uncertainty of voltage is (confidence level 95%, = 2), so: u = 1.2%
d) This standard requires that the input impedance of the measuring amplifier is 100 times higher than the impedance of the hydrophone, so the voltage coupling loss can be introduced to be about 1.2%:
CB/T 17251-1998
) This standard requires that the signal frequency uncertainty is 0.5 (confidence level 95%, -2), then: MmEe - 0. 25%
Therefore, Class B component
: 3. 2% (0. 3 dB
13 Synthetic standard uncertainty Www.bzxZ.net
In the calibration of hydrophone acceleration sensitivity, the standard uncertainty of the calibration result includes Class A component and Class B component. Obviously, they are unrelated to each other. Therefore, the synthetic standard uncertainty is their square root value: u— Vu +
A4 Expanded uncertainty
The expanded uncertainty is expressed as U. Therefore, the calibration result of the hydrophone acceleration sensitivity can be expressed as M.-M, ±U
The combined uncertainty is multiplied by the included factor to obtain: Uk-uc
(A3)
-{A4）
-(A5)
The included value is selected according to the confidence level required for the interval of crown, second (!), generally within the range of 2 to 3 weeks, when table = 2, the interval setting level is about 95%, when a higher confidence level is required, it can be taken as = 3, at this time the confidence level is about 9%. This standard recommends starting from 2.
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