JJG 1017-2007 1kHz～1MHz Standard Hydrophone Verification Procedure JJG1017-2007 Standard download decompression password: www.bzxz.net
This procedure is applicable to the initial verification, subsequent verification and in-use inspection of standard hydrophones in the frequency range of 1kHz～1MHz. The calibration of the sending current response level of the standard transmitter in this frequency range can also be implemented as a reference.

This regulation refers to the following documents:
GB/T3102.7—1993 "Acoustic Quantities and Units"
GB/T3223—1994 "Free Field Calibration Method for Acoustic Underwater Acoustic Transducers"
GB/T3947—1996 "Terms of Acoustics"
GB/T4128—1995 "Acoustic Standard Hydrophone"
GJB1727—1993 "Verification Procedure for Medium Frequency Primary Standard Hydrophone"
JJF1001—1998 "General Metrology Terms and Definitions"
JJF1034—2005 "Terms of Acoustic Metrology Terms and Definitions"
JJF1059—1999 "Evaluation and Expression of Measurement Uncertainty"
IEC60565Ed.2:2006, Underwater acoustics-hydrophones-calibrationin the frequency range0.01Hzto1MHz
When using this procedure, attention should be paid to using the currently valid versions of the above-mentioned references.
1 Scope (1)
2 References (1)
3 Terms and units of measurement (1)
3.1 Electrical terminals of a reciprocal transducer (1)
3.2 Electrical transfer impedance of a transducer pair (1) 3.3 Electrical transfer
impedance modulus (2) 3.4
Open circuit voltage of a hydrophone (2)
3.5 Reference centre (2)
4 Overview (2)
5 Metrological performance requirements (2)
5.1 Free field [voltage] sensitivity [level] (2)
5.2 Free field sensitivity level frequency response (2)
6 General technical requirements (2)
6.1 Appearance and structure (2)
6.2
6.3 Working normality (3) 6.4
Marking and factory calibration data (3)
7 Control of measuring instruments (3)
7.1 Verification conditions (3)
7.2 Verification items (4)
7.3 Verification methods (5)
7.4 Processing of verification results (10)
7.5 Verification cycle (10)
Appendix A Pulse sound calibration technology (11)
Appendix B Verification of reciprocity verification conditions (13) Appendix
C Electric load correction (15)
Appendix D Format of the inner pages of the verification certificate and verification result notice (16)
Appendix E Measurement uncertainty evaluation examples (18)

National Metrology Verification Regulation of the People's Republic of China JJG10172007
1kHz-1MHz Standard Hydrophone
Standard Hydrophones in the Frequency Range1 kHz to 1 MHz
Promulgated on 2007-02-28
Implementation on 2007-0528
Promulgated by the General Administration of Quality Supervision, Inspection and Quarantine JJG 1017--2007
1kHz～1 MHz Standard Hydrophone
Verification Regulation of StandardHydrophones in the Frequency Range1 kHz to 1 MHz
JJG 1017—2007
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine on February 28, 2007, and came into effect on May 28, 2007.
Responsible unit: National Technical Committee on Acoustic Metrology Main drafting unit: 715th Institute of China Shipbuilding Industry Corporation Participating drafting units: Institute of Acoustics, Chinese Academy of Sciences China Institute of Testing Technology
This regulation is entrusted to the National Technical Committee on Acoustic Metrology for interpretation Main drafters:
JJG 1017—2007
Wang Yuebing (715th Institute of China Shipbuilding Industry Corporation) Chen Yi (75th Institute of China Shipbuilding Industry Corporation) Yuan Wenjun (715th Institute of China Shipbuilding Industry Corporation) Participating drafters:
Zhu Houqing (Institute of Acoustics, Chinese Academy of Sciences) Shang Guohua (China Institute of Testing Technology) 1 Scope·
2 References ·
3 Terms and units of measurement
3.1 Electrical terminals of reciprocal transducers ·
3.2 Electrical transfer impedance of transducer pairs
3.3 Electrical transfer impedance norm
3.4 ​​Open circuit voltage of hydrophones ·
3.5 Reference center ·
4 Overview ·
5 Metrological performance requirements
5.1 Free-field [voltage] sensitivity [level] 5.2 Free-field sensitivity level frequency response
6 General technical requirements ·
6.1 Appearance structure 6.2 Working adaptability
6.3 Working normality
6.4 Marking and factory calibration data
7 Measuring instrument control
7.1 Verification conditions
7.2 Verification items
7.3 Verification methods ...
7.4 Processing of verification results
7.5 Verification cycle
Appendix A Pulse sound calibration technology
Appendix B Verification of verification conditions of reciprocity method
Appendix C Electric load correction www.bzxz.net
JJG 1017--2007
Appendix D Inner page format of verification certificate and verification result notice Appendix E Measurement uncertainty assessment example
(1)
JJG 1017--2007
1kHz~1MHz standard hydrophone verification procedure
This procedure refers to the free field reciprocity method calibration in the International Electrotechnical Commission IEC60565Ed.2:2006 "Calibration of underwater acoustic hydrophones in the frequency range of 0.01Hz~1MHz". 1 Range
This procedure is applicable to the initial verification, subsequent verification and in-use inspection of standard hydrophones in the frequency range of 1kHz-1MHz. The calibration of the standard transmitter's sending current response level in this frequency range can also refer to the hot line. 2 References
This specification references the following documents:
GB/T 3102.7-—-1993
GB/T 3223---1994
GB/T 3947---1996
GB/T 4128--1995
GJB 1727--1993
JJF 1001---1998
JJF 1034—2005
JJF 10591999
"Quantities and Units of Acoustics"
"Free-Field Calibration Method for Underwater Acoustic Transducers"
"Terms and Terms of Acoustics"
"Acoustics. Standard hydrophones
Verification procedures for medium frequency first-level standard hydrophones"General metrological terms and definitions
Terminology and definitions for acoustic metrology
Evaluation and expression of measurement uncertainty
IEC 60565 Ed.2: 2006, Underwater acoustics-hydrophones-calibration in the frequencyrange 0.01 Hz to 1 MHz
When using this procedure, attention should be paid to the use of the current valid versions of the above-mentioned references. Terms and measurement units
This procedure adopts the relevant terms and definitions in GB/T3947--1996, JJF1001---1998, and JF1034-~2005. This procedure adopts the quantities and units specified in GB/T3102.7--1993. In this procedure, unless otherwise specified, all voltages, currents, and sound pressures refer to effective values. 3.1 Electrical terminals of a reciprocal transducer The terminals at which the open circuit voltage is measured when used as a hydrophone and the terminals at which the transmitted current is measured when used as a transmitter. NOTE If the transducer is immersed in water, the terminal with the lowest impedance to the water is called the "low terminal" and the other terminal is called the "high terminal". 3.2 Electrical transfer impedance of a transducer pair The complex ratio of the instantaneous open circuit voltage across the hydrophone to the instantaneous current through the transmitter when the transmitter and hydrophone are placed in a free acoustic field with their principal axes aligned and mutually aligned. Unit: Ohm, 2.
1. Electrical transfer impedance is a complex number.
2. Since electrical transfer impedance depends on the acoustic field conditions and the electrical loading of the transmitter and the hydrophone, the relevant conditions should be stated together with the terminals at which the voltage and current are measured.
JJG 1017-2007
3.3 Electrical transfer impedance magnitude The magnitude of the electrical transfer impedance of the transducer pair.
Unit: Ohm, 2.
3.4 ​​Open-circuit voltage at hydrophone The voltage present at the output end of the hydrophone when no current flows through it. Unit: Volt [Te], V.
3.5 Reference centre The point on or near the transducer at which the acoustic receiving sensitivity of the transducer is defined. It is recommended to select a point at or near the centre of the working surface of the transducer as the reference centre. It is usually the geometric centre of the transducer, such as the centre of the sphere of a spherical piezoelectric ceramic transducer.
4 Overview
The standard hydrophone is used to calibrate and measure the hydrophone and the sound pressure in water. It is composed of piezoelectric or other sensitive elements and corresponding structures. Under the action of sound waves, it can generate an open-circuit voltage value proportional to the sound pressure. 5 Metrological performance requirements
5.1 Free-field [voltage] sensitivity [level]
For standard hydrophones used at frequencies below 100kHz, the free-field sensitivity level should not be less than 215dB (reference value: 1VluPa); for standard hydrophones used in the frequency range of 100kHz to 1MHz, the free-field sensitivity level should not be less than -250 dB.
1. Free-field sensitivity refers to the average value of the flat part of the sensitivity frequency response curve. 2. The sensitivity here is the open-circuit voltage sensitivity. 5.2 Free-field sensitivity level frequency response
For standard hydrophones used at frequencies below 100kHz, the fluctuation of the free-field sensitivity level should not exceed ±3.0dB; for standard hydrophones used in the frequency range of 100kHz to 1MHz, the fluctuation of the free-field sensitivity level should not exceed ±4.0dB.
6 General technical requirements
6.1 Appearance structure
6.1.1 The reference center position and calibration direction of the standard hydrophone should be clearly marked. 6.1:2. The surface of the standard hydrophone in contact with water should be smooth, non-porous and wettable by water. 6.2 Work adaptability
6.2.1 The characteristics and construction of the standard hydrophone should be suitable for measurement under environmental conditions of water temperature (5～30)℃ and water depth (0～10)m.
6.2.2 The materials and structures used in the standard hydrophone should have long-term stability, and all parts of the hydrophone exposed to water should be made of corrosion-resistant materials. 6.2.3 High-impedance sensitive elements should be electrostatically shielded, and the electrostatic shield and the metal 2
shell of the standard hydrophone exposed to water should be connected to the shielding wire of the cable.
6.3 Normal operation
JJG 1017--2007
6.3.1 For standard hydrophones without preamplifiers, when the frequency is lower than 100kHz, the insulation resistance measured at the electrical end should be greater than 100MQ (test voltage 100V); when the frequency is higher than 100kHz, the insulation resistance should be greater than 100kQ (test voltage 100V). The capacitance value measured at the electrical terminal should not differ from the value provided in the instruction manual by more than ±20%.
6.3.2 For standard hydrophones with preamplifiers, when a vibration signal acts on the sensitive element of the hydrophone, the electrical terminal should have a corresponding voltage output.
6.3.3 If the fixture used in the measurement has an effect on the sensitivity of the standard hydrophone, the fixture used for the calibration of the standard hydrophone should be consistent with that used in actual use.
6.4 Marking and factory calibration information
6.4.1 The standard hydrophone should have the following clear and durable markings: (1) Manufacturer's name:
(2) Product model;
(3) Product serial number.
6.4.2 Each standard hydrophone should be accompanied by the corresponding factory calibration information. The factory calibration information should include the sound pressure sensitivity level frequency response data or curve of the standard hydrophone, and the definition of the signal line, ground line and shielding line. Standard hydrophones with preamplifiers should also have power supply lines marked and supply voltage values ​​indicated: For standard hydrophones without preamplifiers, the cable length should be consistent with that during calibration. 6.4.3 Parts that do not require adjustment should be protected by sealing or marking to avoid affecting the performance of the standard hydrophone.
7 Control of measuring instruments
Control of measuring instruments includes initial calibration, subsequent calibration and inspection during use. 7.1 Calibration conditions
7.1.1 Calibration environmental conditions
Room temperature: 10℃～30℃;
Humidity: 30%~～90%;
Water temperature: 5℃30℃.
7.1.2. Calibration equipment
Calibration equipment includes calibration water area, auxiliary transducer and electronic instruments. Among them, the current sampler and waveform acquisition instrument are metrological standards, and other electronic instruments, auxiliary transducers and calibration water areas are supporting equipment. 7.1.2.1 Measuring standards
(1) Current sampler: It can be a current converter or a precision resistor with a small resistance value. Its accuracy should be better than ±1%.
(2) Waveform acquisition instrument: The A/D conversion bit number is not less than 8 bits, and the sampling frequency is at least 4 times higher than the signal frequency. 7.1.2.2 Supporting equipment
(1) Calibration water area and signal
JJG 1017--2007
1) Distance between the transmitting transducer and the hydrophone The distance between the transmitting transducer and the reference center of the hydrophone should be large enough to make the hydrophone in the far field of the transmitting transducer. The distance between the two should meet the requirements of formula (1). d
,d >ai,d>az
Where: d---the distance between the transmitting transducer and the reference center of the hydrophone, m; a1---the maximum size of the transmitting transducer sensitive element, m: a2---the maximum size of the hydrophone sensitive element, m;---the wavelength of the underwater sound wave corresponding to the calibration frequency, ms2) The calibration signal can be a continuous sinusoidal signal or a pulse modulated sinusoidal signal. (1)
3) When using a continuous sinusoidal signal, in order to obtain a free field, the calibration should be carried out in an anechoic pool or open water, and the sound propagation attenuation in the area where the transducer and hydrophone are placed should be checked before the calibration, and the deviation of its value from the ideal free field should not exceed ±0.5dB.
4) When using pulse modulated sinusoidal signals for verification, the test can be carried out in an anechoic pool, a non-anechoic pool or other confined water area, but the pulse width must meet the requirements of formulas (A.1), (A.2), (A.3), (A.4), (A.5), (A.6) and (A.7) in Appendix A. 5) When using pulse modulated sinusoidal signals for verification, in order to reduce the impact of reverberation sound on direct sound, the pulse repetition period should meet the requirements of formula (A.8) in Appendix A. (2) Auxiliary transducers
Nonlinearity checks should be performed on the transmitting transducer and the reciprocal transducer. When the frequency is less than 100kHz, the nonlinearity should not exceed ±0.2dB; when the frequency is greater than or equal to 100kHz, the nonlinearity should not exceed ±0.5dB. The reciprocity check should be performed on the reciprocal transducer. When the frequency is less than 100kHz, the non-reciprocity shall not exceed ±0.5dB; when the frequency is greater than or equal to 100kHz, the non-reciprocity shall not exceed ±1.0dB. (3) Electronic instruments
1) Signal source: The frequency stability shall be better than ±0.02%/h, and the frequency indication error shall not exceed ±0.02%; the maximum output voltage shall not be less than 1V peak, and the voltage indication error shall not exceed ±1%. 2) Measuring amplifier: The input impedance shall be at least 100 times higher than the hydrophone impedance; the gain error shall not exceed ±0.1 dB.
3) Electronic switch: The crosstalk between the two channels shall be less than -80dB. 4) Power amplifier: The output impedance shall match the impedance of the transmitting transducer, and the output waveform distortion (THD+N) shall not exceed 2%.
5 Filter: 1/3 or 1/1 octave filter, or a bandpass filter with an adjustable bandwidth, with an attenuation slope of not less than 48dB/octave.
.6) Megaohmmeter: test voltage 100V, maximum allowable error of insulation resistance measurement ±10%. 7) Capacitance meter: capacitance value measurement range not less than 100μF, maximum allowable error of capacitance measurement ±5%. 8) Computer: with instrument control interface.
7.2·Verification items
The initial verification, subsequent verification and in-use inspection items of standard hydrophone are shown in Table 1.4
JJG 1017---2007
Table 1 List of initial verification, subsequent verification and in-use inspection items of standard hydrophone Item
Appearance inspection
Insulation resistance
Free field sensitivity [level]
Free field sensitivity level Frequency response
Initial verification
Subsequent verification
1. When the standard hydrophone is equipped with a preamplifier, the insulation resistance and capacitance of the hydrophone are not verified. 2. “+” indicates items that need to be inspected, and “” indicates items that do not need to be inspected. 7.3 Verification method
7.3.1. Appearance inspection
In-use inspection
The standard hydrophone should have clear markings, including the manufacturer's name, product model, product serial number, etc. The appearance should be intact, without mechanical damage that affects normal operation. The factory calibration data should meet the requirements of 6.4.2. 7.3.2. Insulation resistance
When the standard hydrophone is not equipped with a preamplifier, the sensitive component part of the standard hydrophone is placed in water, and the ends of the cable of the standard hydrophone are connected to the two ends of the megohmmeter. The measured insulation resistance value should meet the requirements of 6.3.1. 7.3.3 Capacitance
When the standard hydrophone is not equipped with a preamplifier, the cable of the standard hydrophone is not terminated at both ends of the capacitance meter. The measured capacitance value should meet the requirements of 6.3.1.
7.3.4 Free field sensitivity [level]
First calibration and subsequent calibration: Calibration shall be carried out by the free field reciprocity method. In-use inspection: Carry out in accordance with 4) of (4) in 7.3.4.3. 7.3.4.1 Verification principle
When using the free field reciprocity method for verification, three transducers must be used: transmitting transducer F, reciprocal transducer H and hydrophone J. The principle diagram of the verification method is shown in Figure 1. The measurement is carried out in three steps: The first step is shown in Figure 1 (a): Under free field conditions, F transmits sound waves and H receives sound waves. The reference centers of F and H are separated by a distance of dei. The open circuit voltage UH of H and the transmitting current IF of F are measured. The electrical transfer impedance modulus of F and H is calculated according to formula (2).
Where: "Zerl——Electrical transfer impedance modulus between F and H, α; UH
-Open circuit voltage value of H when F is transmitting, V;
I—--Emission current value of F, A.
The second step is shown in Figure 1 (b): Under free field conditions, F transmits sound waves and J receives sound waves. The reference centers of F and J are dE apart. The open circuit voltage U of J and the emission current IF of F are measured. The electrical transfer impedance modulus between F and J is calculated according to Formula (3).
—2007
JJG 1017-
Schematic diagram of the test method
Where: iZ! ——Electrical transfer impedance modulus of F and J, α; Ur—Open circuit voltage value of J when F transmits, V; Ip——Emission current value of F, A.
The third step is shown in Figure 1 (c): Under free field conditions, H transmits sound waves and J receives sound waves. The distance between H and the reference center is d. The open circuit voltage UH of J and the emission current In of H are measured. The electrical transfer impedance modulus of F and J is calculated according to formula (4).
Where: Z|Electrical transfer impedance modulus of F and J, α; UHr——Open circuit voltage value of J when H transmits, V; I——Emission current value of F, A.
·The free field sensitivity levels of H and J are calculated according to formulas (5) and (6) respectively: (de du) + 101gJs-120
M=10lgiZ|+10lgZ-10lg|Z|+10lg(EI
M,=10g/Zgl+10g Zm|101g|Zml+ 101g(nd)+101g/s120dEH
Wherein: MH—free field sensitivity level of H, dB (reference value: 1ViuPa); M,—free field sensitivity level of J, dB (reference value: 1V/μPa); Js--—spherical wave reciprocity constant, W/(m·Pa2). Calculate according to formula (7). Js 2
Where:
-density of water, kg/m;
-signal frequency, Hz.
The sending current response levels of H and F are calculated according to formulas (8) and (9) respectively. 6
JJG 1017-2007
Smx =101gl Zml+ 101glZm -10ig|Zml+10g(dm du) 101g/s + 120(8)
Sm=10g/Zml+10gl Zml10g/Zl+1g(mn)10g/s+120dH
Where: Smr—H’s transmission current response level, dB (reference value: 1μPa'm/A); Sre-----F’s transmission current response level, dB (reference value: 1μPa'm/A). (9)
If d=d=d=d during verification, then formulas (5), (6) and (8), (9) can be simplified to formulas (10), (11) and (12) respectively (13Mu = 10n1gl2m(mg/2E gd + lgJs] - 120(10)
M = 10ig1z++ iglzul- Iglzmigat IgJs] -120Sm
7.3.4.2 Calibration device
OfiglZe
The block diagram of the free-field reciprocity method calibration device is shown in Figure 2
Transducer, receiving refers to hydrophone or computer
Signal source
Measurement amplifier
Waveform
Printer
Power amplifier
Electronic switch||tt ||l+igae
s1+120
Wherein, the transmitter refers to the transmitting transducer or reciprocal transformer
Receiver
Figure 2 Block diagram of the free-field reciprocity method calibration device 7.3.4.3 Calibration steps
(1) Preparation of signal and sound field conditions
Transmitter
Prepare the calibration water area and signal in accordance with the provisions of (1) of 7.1.2.2. For water areas that are not frequently used or when the water conditions change, a sound field inspection must be carried out before calibration. The inspection method is shown in Appendix B. (2) Transducer preparation
JJG 1017--2007
1) Prepare the auxiliary transducer for calibration according to the requirements of 7.1.2.2 (2). 2) In order to make the transducer surface fully moist and free of bubbles, the transducer surface should be scrubbed with a detergent that is non-corrosive to rubber and metal, and coated with a wetting agent or immersed in water for at least 1 hour to allow it to reach temperature equilibrium.
3) According to the predetermined plan, the auxiliary transducer and the hydrophone to be tested are combined in pairs (see Figure 1) and fixed in sequence in an appropriate manner at the same depth of the calibration water area. The error should not exceed 0.5 cm at the depth; the distance d between the reference centers of each pair of transducers should be accurately measured, and the measurement uncertainty should not exceed 1%. The calibration directions of the two transducers should be aligned with each other, and the allowable deviation should not exceed 3%. The fixing method and bracket structure should not affect the calibration results; 4) In order to balance the transducer with the water temperature and pressure, the transducer should be placed at the calibration depth of the calibration water area for at least 30 minutes before starting the measurement;
5) If necessary, the linearity and reciprocity of the transducer should be checked. The inspection method is shown in Appendix B. (3) Interference and signal-to-noise ratio check
1) Check the signal-to-noise ratio under actual measurement conditions. Its value should not be less than 30dB. In order to further improve the signal-to-noise ratio of the measurement signal, the collected signal can be averaged multiple times: 2) When applying a pulse signal, check the existence of the crosstalk pulse, and separate the direct wave from the crosstalk by adjusting the pulse width;
3) When applying a continuous signal, the influence of the crosstalk signal on the acoustic signal should be checked and eliminated; 4) When using an auxiliary transducer to transmit, the change in the output open-circuit voltage should not exceed ±0.2dB within ±3° of the calibration direction of the hydrophone to be tested.
（4）Measurement
1) Assemble the calibration device as shown in Figure 2, turn on all instruments and equipment, and preheat for 15 minutes; 2) Select the type of signal required for measurement according to the actual situation, usually a pulse modulated sine signal; 3) Adjust the amplification of the power amplifier to an appropriate value; 4) When the frequency range of the hydrophone to be tested is 1kHz~200kHz or 100.kHz--1MHz, set the operating frequency of the calibration device to 50kHz or 500kHz, and the output waveform of the hydrophone to be tested should have no obvious distortion; 5) Operate the computer and call up the corresponding Measurement program, and input the frequency sequence required for measurement; 6) Control and measure according to the flowchart shown in Figure 3. When the device is set to the panel control state, manual point-by-point measurement can also be performed;
7) Measure the sending current and receiving voltage: 8) Calculate the electrical transfer impedance modulus according to formula (14): U.
Where: Cr-sensitivity of the current sampler; VIA; 1z-electrical transfer impedance modulus of the transmitter and receiver pair, α; Uo-open-circuit output voltage of the hydrophone after amplification and filtering, V; U-output voltage of the current sampler after amplification and filtering, V. (14)
In the process of performing signal sampling and discrete Fourier transform operations, it is required that the operation window length is exactly an integer multiple of the period of the measured signal, that is, the sampling rate must meet the requirements of formula (15): 8=10g/Zgl+10g Zm|101g|Zml+ 101g(nd)+101g/s120dEH
Where: MH—free field sensitivity level of H, dB (reference value: 1ViuPa); M,—free field sensitivity level of J, dB (reference value: 1V/μPa); Js--—spherical wave reciprocity constant, W/(m·Pa2). Calculate according to formula (7). Js 2
Where:
-density of water, kg/m;
-signal frequency, Hz.
The sending current response levels of H and F are calculated according to formulas (8) and (9) respectively. 6
JJG 1017-2007
Smx =101gl Zml+ 101glZm -10ig|Zml+10g(dm du) 101g/s + 120(8)
Sm=10g/Zml+10gl Zml10g/Zl+1g(mn)10g/s+120dH
Where: Smr—H’s transmission current response level, dB (reference value: 1μPa'm/A); Sre-----F’s transmission current response level, dB (reference value: 1μPa'm/A). (9)
If d=d=d=d is taken during the test, then formulas (5), (6) and (8), (9) can be simplified to formulas (10), (11) and (12) respectively (13Mu = 10n1gl2m(mg/2E gd + lgJs] - 120(10)
M = 10ig1z++ iglzul- Iglzmigat IgJs] -120Sm
7.3.4.2 Calibration Device
OfiglZe
The block diagram of the free field reciprocity method calibration device is shown in Figure 2
Transducer, receiving refers to hydrophone or horse computer
Signal source
Measurement amplifier
Waveform
Printer
Power amplifier
Electronic switch
l+igae
s1+120
Among them, the transmitter Refers to the transmitting transducer or reciprocal transformer
Receiver
Figure 2 Block diagram of the free-field reciprocity method calibration device 7.3.4.3 Calibration steps
(1) Preparation of signal and sound field conditions
Transmitter
Prepare the calibration water area and signal in accordance with the provisions of (1) of 7.1.2.2. For water areas that are not frequently used or when water conditions change, a sound field inspection must be carried out before calibration. The inspection method is shown in Appendix B. (2) Transducer preparation
JJG 1017--2007
1) Prepare the auxiliary transducer for calibration according to the requirements of 7.1.2.2 (2). 2) In order to make the transducer surface fully moist and free of bubbles, the transducer surface should be scrubbed with a detergent that is non-corrosive to rubber and metal, and coated with a wetting agent or immersed in water for at least 1 hour to allow it to reach temperature equilibrium.
3) According to the predetermined plan, the auxiliary transducer and the hydrophone to be tested are combined in pairs (see Figure 1) and fixed in sequence in an appropriate manner at the same depth of the calibration water area. The error should not exceed 0.5 cm at the depth; the distance d between the reference centers of each pair of transducers should be accurately measured, and the measurement uncertainty should not exceed 1%. The calibration directions of the two transducers should be aligned with each other, and the allowable deviation should not exceed 3%. The fixing method and bracket structure should not affect the calibration results; 4) In order to balance the transducer with the water temperature and pressure, the transducer should be placed at the calibration depth of the calibration water area for at least 30 minutes before starting the measurement;
5) If necessary, the linearity and reciprocity of the transducer should be checked. The inspection method is shown in Appendix B. (3) Interference and signal-to-noise ratio check
1) Check the signal-to-noise ratio under actual measurement conditions. Its value should not be less than 30dB. In order to further improve the signal-to-noise ratio of the measurement signal, the collected signal can be averaged multiple times: 2) When applying a pulse signal, check the existence of the crosstalk pulse, and separate the direct wave from the crosstalk by adjusting the pulse width;
3) When applying a continuous signal, the influence of the crosstalk signal on the acoustic signal should be checked and eliminated; 4) When using an auxiliary transducer to transmit, the change in the output open-circuit voltage should not exceed ±0.2dB within ±3° of the calibration direction of the hydrophone to be tested.
（4）Measurement
1) Assemble the calibration device as shown in Figure 2, turn on all instruments and equipment, and preheat for 15 minutes; 2) Select the type of signal required for measurement according to the actual situation, usually a pulse modulated sine signal; 3) Adjust the amplification of the power amplifier to an appropriate value; 4) When the frequency range of the hydrophone to be tested is 1kHz~200kHz or 100.kHz--1MHz, set the operating frequency of the calibration device to 50kHz or 500kHz, and the output waveform of the hydrophone to be tested should have no obvious distortion; 5) Operate the computer and call up the corresponding Measurement program, and input the frequency sequence required for measurement; 6) Control and measure according to the flowchart shown in Figure 3. When the device is set to the panel control state, manual point-by-point measurement can also be performed;
7) Measure the sending current and receiving voltage: 8) Calculate the electrical transfer impedance modulus according to formula (14): U.
Where: Cr-sensitivity of the current sampler; VIA; 1z-electrical transfer impedance modulus of the transmitter and receiver pair, α; Uo-open-circuit output voltage of the hydrophone after amplification and filtering, V; U-output voltage of the current sampler after amplification and filtering, V. (14)
In the process of performing signal sampling and discrete Fourier transform operations, it is required that the operation window length is exactly an integer multiple of the period of the measured signal, that is, the sampling rate must meet the requirements of formula (15): 8=10g/Zgl+10g Zm|101g|Zml+ 101g(nd)+101g/s120dEH
Where: MH—free field sensitivity level of H, dB (reference value: 1ViuPa); M,—free field sensitivity level of J, dB (reference value: 1V/μPa); Js--—spherical wave reciprocity constant, W/(m·Pa2). Calculate according to formula (7). Js 2
Where:
-density of water, kg/m;
-signal frequency, Hz.
The sending current response levels of H and F are calculated according to formulas (8) and (9) respectively. 6
JJG 1017-2007
Smx =101gl Zml+ 101glZm -10ig|Zml+10g(dm du) 101g/s + 120(8)
Sm=10g/Zml+10gl Zml10g/Zl+1g(mn)10g/s+120dH
Where: Smr—H’s transmission current response level, dB (reference value: 1μPa'm/A); Sre-----F’s transmission current response level, dB (reference value: 1μPa'm/A). (9)
If d=d=d=d is taken during the test, then formulas (5), (6) and (8), (9) can be simplified to formulas (10), (11) and (12) respectively (13Mu = 10n1gl2m(mg/2E gd + lgJs] - 120(10)
M = 10ig1z++ iglzul- Iglzmigat IgJs] -120Sm
7.3.4.2 Calibration Device
OfiglZe
The block diagram of the free field reciprocity method calibration device is shown in Figure 2
Transducer, receiving refers to hydrophone or horse computer
Signal source
Measurement amplifier
Waveform
Printer
Power amplifier
Electronic switch
l+igae
s1+120
Among them, the transmitter Refers to the transmitting transducer or reciprocal transformer
Receiver
Figure 2 Block diagram of the free-field reciprocity method calibration device 7.3.4.3 Calibration steps
(1) Preparation of signal and sound field conditions
Transmitter
Prepare the calibration water area and signal in accordance with the provisions of (1) of 7.1.2.2. For water areas that are not frequently used or when water conditions change, a sound field inspection must be carried out before calibration. The inspection method is shown in Appendix B. (2) Transducer preparation
JJG 1017--2007
1) Prepare the auxiliary transducer for calibration according to the requirements of 7.1.2.2 (2). 2) In order to make the transducer surface fully moist and free of bubbles, the transducer surface should be scrubbed with a detergent that is non-corrosive to rubber and metal, and coated with a wetting agent or immersed in water for at least 1 hour to allow it to reach temperature equilibrium.
3) According to the predetermined plan, the auxiliary transducer and the hydrophone to be tested are combined in pairs (see Figure 1) and fixed in sequence in an appropriate manner at the same depth of the calibration water area. The error should not exceed 0.5 cm at the depth; the distance d between the reference centers of each pair of transducers should be accurately measured, and the measurement uncertainty should not exceed 1%. The calibration directions of the two transducers should be aligned with each other, and the allowable deviation should not exceed 3%. The fixing method and bracket structure should not affect the calibration results; 4) In order to balance the transducer with the water temperature and pressure, the transducer should be placed at the calibration depth of the calibration water area for at least 30 minutes before starting the measurement;
5) If necessary, the linearity and reciprocity of the transducer should be checked. The inspection method is shown in Appendix B. (3) Interference and signal-to-noise ratio check
1) Check the signal-to-noise ratio under actual measurement conditions. Its value should not be less than 30dB. In order to further improve the signal-to-noise ratio of the measurement signal, the collected signal can be averaged multiple times: 2) When applying a pulse signal, check the existence of the crosstalk pulse, and separate the direct wave from the crosstalk by adjusting the pulse width;
3) When applying a continuous signal, the influence of the crosstalk signal on the acoustic signal should be checked and eliminated; 4) When using an auxiliary transducer to transmit, the change in the output open-circuit voltage should not exceed ±0.2dB within ±3° of the calibration direction of the hydrophone to be tested.
（4）Measurement
1) Assemble the calibration device as shown in Figure 2, turn on all instruments and equipment, and preheat for 15 minutes; 2) Select the type of signal required for measurement according to the actual situation, usually a pulse modulated sine signal; 3) Adjust the amplification of the power amplifier to an appropriate value; 4) When the frequency range of the hydrophone to be tested is 1kHz~200kHz or 100.kHz--1MHz, set the operating frequency of the calibration device to 50kHz or 500kHz, and the output waveform of the hydrophone to be tested should have no obvious distortion; 5) Operate the computer and call up the corresponding Measurement program, and input the frequency sequence required for measurement; 6) Control and measure according to the flowchart shown in Figure 3. When the device is set to the panel control state, manual point-by-point measurement can also be performed;
7) Measure the sending current and receiving voltage: 8) Calculate the electrical transfer impedance modulus according to formula (14): U.
Where: Cr-sensitivity of the current sampler; VIA; 1z-electrical transfer impedance modulus of the transmitter and receiver pair, α; Uo-open-circuit output voltage of the hydrophone after amplification and filtering, V; U-output voltage of the current sampler after amplification and filtering, V. (14)
In the process of performing signal sampling and discrete Fourier transform operations, it is required that the operation window length is exactly an integer multiple of the period of the measured signal, that is, the sampling rate must meet the requirements of formula (15): 8Prepare the auxiliary transducer for calibration as required in (2) of 2: 2) In order to make the transducer surface fully moist and free of bubbles, the transducer surface should be scrubbed with a detergent that is non-corrosive to rubber and metal, and coated with a wetting agent or immersed in water for at least 1 hour to allow it to reach temperature equilibrium before calibration;
3) According to the predetermined plan, the auxiliary transducer and the hydrophone to be tested are combined in pairs (see Figure 1) and fixed in sequence and in an appropriate manner at the same depth of the calibration water area, with an error of no more than ±0.5cm; the distance d between the reference centers of each pair of transducers should be accurately measured, and the measurement uncertainty should be no more than 1%. The calibration directions of the two transducers should be aligned with each other, with an allowable deviation of no more than ±3, and the fixing method and bracket structure should not affect the calibration results; 4) In order to allow the transducer to reach equilibrium with the water temperature and pressure, the transducer should be placed at the calibration depth of the calibration water area for at least 30 minutes before starting the measurement;
5) If necessary, the linearity of the transducer and the reciprocity of the transducer should be checked. The inspection method is shown in Appendix B. (3) Interference and signal-to-noise ratio inspection
1) Check the signal-to-noise ratio under actual measurement conditions. Its value should not be less than 30dB. In order to further improve the signal-to-noise ratio of the measurement signal, the collected signal can be averaged multiple times: 2) When applying a pulse signal, check the existence of the crosstalk pulse, and separate the direct wave from the crosstalk by adjusting the pulse width;
3) When applying a continuous signal, check and eliminate the influence of the crosstalk signal on the acoustic signal; 4) When using an auxiliary transducer to transmit, the change in the output open-circuit voltage should not exceed ±0.2dB within ±3° of the calibration direction of the hydrophone to be tested.
（4）Measurement
1) Assemble the calibration device as shown in Figure 2, turn on all instruments and equipment, and preheat for 15 minutes; 2) Select the type of signal required for measurement according to the actual situation, usually a pulse modulated sine signal; 3) Adjust the amplification of the power amplifier to an appropriate value; 4) When the frequency range of the hydrophone to be tested is 1kHz~200kHz or 100.kHz--1MHz, set the operating frequency of the calibration device to 50kHz or 500kHz, and the output waveform of the hydrophone to be tested should have no obvious distortion; 5) Operate the computer and call up the corresponding Measurement program, and input the frequency sequence required for measurement; 6) Control and measure according to the flowchart shown in Figure 3. When the device is set to the panel control state, manual point-by-point measurement can also be performed;
7) Measure the sending current and receiving voltage: 8) Calculate the electrical transfer impedance modulus according to formula (14): U.
Where: Cr-sensitivity of the current sampler; VIA; 1z-electrical transfer impedance modulus of the transmitter and receiver pair, α; Uo-open-circuit output voltage of the hydrophone after amplification and filtering, V; U-output voltage of the current sampler after amplification and filtering, V. (14)
In the process of performing signal sampling and discrete Fourier transform operations, it is required that the operation window length is exactly an integer multiple of the period of the measured signal, that is, the sampling rate must meet the requirements of formula (15): 8Prepare the auxiliary transducer for calibration as required in (2) of 2: 2) In order to make the transducer surface fully moist and free of bubbles, the transducer surface should be scrubbed with a detergent that is non-corrosive to rubber and metal, and coated with a wetting agent or immersed in water for at least 1 hour to allow it to reach temperature equilibrium before calibration;
3) According to the predetermined plan, the auxiliary transducer and the hydrophone to be tested are combined in pairs (see Figure 1) and fixed in sequence and in an appropriate manner at the same depth of the calibration water area, with an error of no more than ±0.5cm; the distance d between the reference centers of each pair of transducers should be accurately measured, and the measurement uncertainty should be no more than 1%. The calibration directions of the two transducers should be aligned with each other, with an allowable deviation of no more than ±3, and the fixing method and bracket structure should not affect the calibration results; 4) In order to allow the transducer to reach equilibrium with the water temperature and pressure, the transducer should be placed at the calibration depth of the calibration water area for at least 30 minutes before starting the measurement;
5) If necessary, the linearity of the transducer and the reciprocity of the transducer should be checked. The inspection method is shown in Appendix B. (3) Interference and signal-to-noise ratio inspection
1) Check the signal-to-noise ratio under actual measurement conditions. Its value should not be less than 30dB. In order to further improve the signal-to-noise ratio of the measurement signal, the collected signal can be averaged multiple times: 2) When applying a pulse signal, check the existence of the crosstalk pulse, and separate the direct wave from the crosstalk by adjusting the pulse width;
3) When applying a continuous signal, check and eliminate the influence of the crosstalk signal on the acoustic signal; 4) When using an auxiliary transducer to transmit, the change in the output open-circuit voltage should not exceed ±0.2dB within ±3° of the calibration direction of the hydrophone to be tested.
（4）Measurement
1) Assemble the calibration device as shown in Figure 2, turn on all instruments and equipment, and preheat for 15 minutes; 2) Select the type of signal required for measurement according to the actual situation, usually a pulse modulated sine signal; 3) Adjust the amplification of the power amplifier to an appropriate value; 4) When the frequency range of the hydrophone to be tested is 1kHz~200kHz or 100.kHz--1MHz, set the operating frequency of the calibration device to 50kHz or 500kHz, and the output waveform of the hydrophone to be tested should have no obvious distortion; 5) Operate the computer and call up the corresponding Measurement program, and input the frequency sequence required for measurement; 6) Control and measure according to the flowchart shown in Figure 3. When the device is set to the panel control state, manual point-by-point measurement can also be performed;
7) Measure the sending current and receiving voltage: 8) Calculate the electrical transfer impedance modulus according to formula (14): U.
Where: Cr-sensitivity of the current sampler; VIA; 1z-electrical transfer impedance modulus of the transmitter and receiver pair, α; Uo-open-circuit output voltage of the hydrophone after amplification and filtering, V; U-output voltage of the current sampler after amplification and filtering, V. (14)
In the process of performing signal sampling and discrete Fourier transform operations, it is required that the operation window length is exactly an integer multiple of the period of the measured signal, that is, the sampling rate must meet the requirements of formula (15): 8
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