JP2013219445A - Sensor reception sensitivity measuring method and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the sensor reception sensitivity of a pressure sensor.SOLUTION: A signal generator 10 generates an exciting signal having predetermined frequency components and outputs that to an amplifier 12. The amplifier 12 amplifies the exciting signal and outputs that to an exciter 14. An actuator 16 provided on the exciter 14 generates mechanical vibrations according to the exciting signal outputted from the amplifier 12. A pressure sensor 20 is placed on a sensor stand 22. A weighting converter 18 is put between the pressure sensor 20 and the actuator 16. An analyzer 24 obtains an electric constant of the weighting converter 18, and obtains force added to the pressure sensor 20. The analyzer 24 obtains voltage outputted from the pressure sensor 20. Sensor reception sensitivity is obtained on the basis of the force added to the pressure sensor 20, the voltage outputted from the pressure sensor 20, and a contact area between the weighting converter 18 and the pressure sensor 20.

Description

  The present invention relates to a sensor reception sensitivity measuring method and system, and more particularly to a method and system for measuring sensor reception sensitivity indicating the relationship between the magnitude of sound pressure applied to a pressure sensor and a detection value by the pressure sensor.

  A sonar that is mounted on a ship, a fish finder or the like and searches for targets such as underwater obstacles and organisms is widely used. The sonar transmits sound waves into the water and receives sound waves reflected by the target. Then, based on the analysis of the received sound wave, the distance to the target and the direction are measured, and the image data of the target is generated. Alternatively, the sonar does not transmit sound waves but receives sound waves radiated from the target, and measures the direction of the target and generates image data of the target.

  As a device that transmits and receives a sound wave, a transducer that converts an electric signal into a sound wave and a transducer as a wave receiver that converts a sound wave into an electric signal are used. Since the transmitter and the receiver have reversible properties, it is possible to transmit and receive with a single transducer by temporally switching between transmission and reception. In addition, separate transducers dedicated to transmission and reception may be used.

  A receiving sensor includes a pressure sensor using a piezoelectric material. The piezoelectric material is a material that outputs a voltage according to deformation caused by an external force and deforms according to the applied voltage. In the following Patent Document 1, such a pressure sensor is described as a wave receiving type piezoelectric element.

JP-A-6-269091

  When a pressure sensor is used as a receiving transducer, sonar design requires sensor sensitivity of the pressure sensor. The sensor reception sensitivity is defined as the ratio of the voltage output from the pressure sensor to the sound pressure of the sound wave applied to the pressure sensor.

  As a method of measuring sensor reception sensitivity, there is a method of measuring an output voltage of a pressure sensor disposed in water. That is, a sound wave generator and a sound pressure sensor are arranged in a water tank filled with water, and sound waves having a known sound pressure are radiated to the pressure sensor. The voltage output from the pressure sensor is measured, and the sensor reception sensitivity is obtained by dividing the measured voltage by the sound pressure of the sound wave radiated to the pressure sensor.

  However, in such a method, the voltage output from the pressure sensor is not only a voltage based on the sound wave directly generated by the pressure sensor and received from the pressure sensor, but also from the sound wave generator. In some cases, a voltage based on a sound wave received by a pressure sensor after being reflected by a water surface is included. As a result, when performing measurements based on sound waves of a predetermined wavelength, it is difficult to measure low frequencies with long wavelengths depending on the size of the water tank due to interference between the direct wave and the reflected wave. growing.

  An object of this invention is to measure the sensor receiving sensitivity of a pressure sensor with high precision.

  The present invention relates to a sensor reception sensitivity measurement method for measuring a sensor reception sensitivity indicating a relationship between a magnitude of a sound pressure applied to a pressure sensor and a detection value by the pressure sensor, and vibration is generated by an exciter. Applying a vibration to a weighted transducer that detects the magnitude of vibration, applying vibration to the pressure sensor via the weighted transducer, information indicating a detection value by the pressure sensor, and the weighted transducer And a step of displaying or storing information indicating the detection value as information for sensor reception sensitivity measurement.

  In addition, the present invention provides a sensor reception sensitivity measurement system that measures the sensor reception sensitivity indicating the relationship between the magnitude of the sound pressure applied to the pressure sensor and the detection value of the pressure sensor, and that adds vibration. A vibration generator, a weighting transducer that detects the magnitude of the vibration while giving vibration generated from the vibrator to the pressure sensor, a detection value by the pressure sensor, and a detection value by the weighting transducer And an analyzer for measuring the sensor reception sensitivity.

  In the sensor reception sensitivity measuring system according to the present invention, preferably, the detected value by the weighted transducer has a unit of force, and the analyzer is detected by the pressure sensor and by the weighted transducer. In addition to the detected value, the sensor receiving sensitivity is measured based on the contact area between the weighted transducer and the pressure sensor.

  In the sensor receiving sensitivity measurement system according to the present invention, the vibrator generates vibration having white noise characteristics, and the analyzer detects a detection value by the pressure sensor and a detection by the weighting converter. A frequency analysis unit that performs frequency analysis on the value; and a frequency characteristic measurement unit that measures frequency characteristics of the sensor reception sensitivity based on the frequency analysis.

  ADVANTAGE OF THE INVENTION According to this invention, the sensor receiving sensitivity of a pressure sensor can be measured with high precision.

It is a figure which shows the structure of the sensor receiving sensitivity measuring system which concerns on this invention. It is a figure which shows the example of a pressure sensor. It is a figure which shows the example of a weighting converter. It is a figure which shows the frequency characteristic of sensor receiving sensitivity. It is an enlarged view of a low frequency band showing frequency characteristics of sensor reception sensitivity. It is a figure which shows a mode that the pressure sensor was accommodated in the housing | casing.

  FIG. 1 shows the configuration of a sensor receiving sensitivity measurement system according to an embodiment of the present invention. The sensor received wave sensitivity measuring system applies vibration to the pressure sensor 20 and measures the sensor received wave sensitivity based on the voltage output from the pressure sensor 20. The pressure sensor 20 to be measured may be a pressure sensor used for a general acoustic device in addition to those used for sonar.

  The signal generator 10 generates an excitation signal having a predetermined frequency component and outputs it to the amplifier 12. The excitation signal is, for example, a signal having white noise characteristics. Such vibration corresponding to the white noise signal is applied to the pressure sensor 20, and frequency analysis is performed for the output voltage of the pressure sensor 20 multiple times by the analyzer 24 described later. Then, by adding and averaging the frequency analysis results obtained over a plurality of times, it becomes possible to extract signal components in a wide frequency range.

  The amplifier 12 amplifies the excitation signal and outputs it to the vibrator 14. The vibrator 14 includes an actuator 16 that generates mechanical vibration. The actuator 16 generates mechanical vibrations according to the excitation signal output from the amplifier 12.

  When measuring the sensor reception sensitivity, the pressure sensor 20 is placed on the sensor base 22. The actuator 16 and the weight converter 18 have a structure for efficiently transmitting the vibration from the actuator 16 to the weight converter 18. The weighted transducer 18 and the pressure sensor 20 have a contact structure in which the transmission loss for vibration transmitted from the weighted transducer 18 to the pressure sensor 20 is minimized. The sensor base 22 is preferably formed of a rigid material in order to reliably transmit the mechanical vibration of the weighted transducer 18 to the pressure sensor 20. In order to describe this state more specifically, examples of the pressure sensor 20 and the weighted transducer 18 will be described.

  An example of the pressure sensor 20 is shown in FIG. The pressure sensor 20 is also referred to as a hydrophone. The pressure sensor 20 includes a cylindrical piezoelectric material 26, two circular electrodes 28A and 28B sandwiching the piezoelectric material 26, and conductive wires 30A and 30B drawn from the electrodes 28A and 28B, respectively. Conductive wires 30 </ b> A and 30 </ b> B of the pressure sensor 20 are connected to the analyzer 24. When the piezoelectric material 26 is deformed by the applied vibration, a voltage corresponding to the applied vibration is output from the pair of conductors 30A and 30B. In addition to such a pressure sensor 20, other general pressure sensors such as a pressure sensor in which a plurality of piezoelectric materials 26 are stacked with electrodes interposed therebetween can be used as a sensor receiving sensitivity measurement target.

  The pressure sensor 20 is placed on the sensor base 22 with the electrode 28B as a bottom surface. Vibration is given to the electrode 28A from the weighted transducer 18. Due to the vibration applied to the electrode 28A, the pressure sensor 20 outputs a voltage corresponding to the vibration from the conducting wires 30A and 30B.

  FIG. 3 shows an example of the weight converter 18. This weight converter 18 is also called a load cell. When a force is applied to the load protrusion 32 in the downward direction in FIG. 3 in a state where the transducer bottom surface 36 is fixed, the electrical state of the conductors 34A and 34B changes according to the applied force. For example, when the weight converter 18 is a piezoelectric type, a voltage corresponding to the applied force is output from the conductors 34A and 34B. When the weight converter 18 is a strain gauge type, electric constants such as capacitance, electric resistance, and inductance between the conducting wires 34A and 34B change according to the applied force. The measuring instrument to which the conducting wires 34A and 34B are connected measures the force applied to the weighted transducer 18 based on the electrical state of the conducting wires 34A and 34B. The unit of force measured by the measuring instrument is Newton (N), kg weight (kgf), or the like.

  The weighted transducer 18 is sandwiched between the actuator 16 and the pressure sensor 20 so that the transducer bottom surface 36 is in contact with the electrode 28 </ b> A and the weighted protrusion 32 is in contact with the actuator 16. The conducting wires 34A and 34B of the weighting converter 18 are connected to an analyzer 24 as a measuring instrument.

  As described above, by arranging the pressure sensor 20 and the weighting transducer 18, vibration is applied to the pressure sensor 20 from the actuator 16 via the weighting transducer 18. At the same time, the electrical constant between the conductive wires 34 </ b> A and 34 </ b> B of the weight converter 18 and the voltage output from the pressure sensor 20 are acquired by the analyzer 24.

  Next, processing for measuring the sensor receiving sensitivity will be described. First, in the state where the pressure sensor 20 and the weighting converter 18 are arranged as shown in FIG. 1, the actuator 16 of the vibrator 14 is vibrated according to the vibration signal, and the pressure sensor 20 is vibrated.

  The analyzer 24 acquires the electrical constant of the weighted converter 18 and obtains the force F applied to the pressure sensor 20. Then, the force F is converted to a frequency domain value F (f) by a fast Fourier transform process. The analyzer 24 acquires the voltage V output from the pressure sensor 20. Then, the voltage V is converted into a value V (f) in the frequency domain by a fast Fourier transform process. The force F (f) and voltage V (f) are functions with respect to the frequency f. The analyzer 24 calculates the sensor reception sensitivity M (f) based on the following (Equation 1).

    (Expression 1) M (f) = V (f) · S / F (f)

  Here, S is a contact area between the weighted transducer 18 and the pressure sensor 20, and is an area where the transducer bottom surface 36 and the electrode 28A are in contact with each other. In the following description, the value of the frequency domain expression is denoted by the symbol “(f)”, and is distinguished from the value of the time domain expression without the symbol.

FIG. 4 shows frequency characteristics of sensor reception sensitivity. The horizontal axis represents frequency, and the vertical axis represents sensor reception sensitivity. Here, the sensor reception sensitivity is represented by a decibel value (dB · V / μPa) with 0 when a voltage of 1 V is output with respect to a sound pressure of 1 μPa. That is, the sensor reception sensitivity of FIG. 4 is 20 log [when the unit of voltage V (f) is Volt V, the unit of force F (f) is Newton N, and the unit of contact area S is square meter m ² . M (f) × 10 ⁻⁶ ]. FIG. 5 is an enlarged view of the low frequency band of 0 to 40 Hz. The analyzer 24 may display the obtained sensor reception sensitivity on a display or may store it in a memory. The frequency characteristic of sensor reception sensitivity is used for calibration with respect to variations in sensor reception sensitivity due to differences in frequency, for example. That is, the user of the pressure sensor 20 may use the frequency characteristic of the sensor reception sensitivity as calibration data of the pressure sensor 20.

  The analyzer 24 may display each value of the force F (f) and the voltage V (f) on a display. In this case, the measurer may perform an operation of obtaining the sensor reception sensitivity M (f) according to (Equation 1) based on the display on the display. The analyzer 24 may store information indicating the force F (f) and the voltage V (f) in its own memory. Then, using the information stored in the memory, an external computer may execute processing for obtaining the sensor reception sensitivity M (f).

  (Equation 1) is obtained as follows. First, the pressure P applied to the pressure sensor 20 is obtained by dividing the force F applied to the pressure sensor 20 by the contact area S. Therefore, the pressure P is expressed by the following (Equation 2).

    (Expression 2) P = F / S

  The sensor reception sensitivity M is obtained by dividing the voltage V output from the pressure sensor 20 by the pressure P. Therefore, the sensor reception sensitivity M is expressed by the following (Equation 3).

    (Expression 3) M = V / P

  By substituting (Equation 2) into (Equation 3) and eliminating the pressure P, the sensor reception sensitivity M in the time domain shown in the following (Equation 4) is obtained. (Equation 1) is obtained by converting (Equation 4) into a frequency domain value.

    (Expression 4) M = V · S / F

  In the above description, the processing is described in which the vibration signal is a signal having a predetermined frequency component, the frequency analysis is performed on the force F and the voltage V, and the sensor receiving sensitivity is obtained using (Equation 1). In addition to such processing, processing in which the excitation signal is a single-frequency continuous waveform signal, that is, a sine wave signal, may be executed. In this case, the force F and the voltage V are obtained for one frequency of the sine wave signal, and the sensor reception sensitivity M for the frequency is obtained based on (Equation 4). By obtaining the sensor reception sensitivity M while scanning the frequency of the sine wave signal as the excitation signal, the frequency characteristic similar to the frequency characteristic shown in FIGS. 4 and 5 can be obtained.

  The processing for obtaining the sensor reception sensitivity M for each frequency may be executed by the calculation of the analyzer 24. The analyzer 24 may display each value of the force F and the voltage V on the display, and the measurer may obtain the sensor reception sensitivity M for each frequency according to (Equation 4). Furthermore, the analyzer 24 may store information indicating the force F and the voltage V in its own memory. Then, an external computer may execute processing for obtaining the sensor reception sensitivity M using information stored in the memory.

  According to the sensor reception sensitivity measuring system and the measurement method according to the present invention, the sensor reception sensitivity is obtained based on the vibration directly applied from the vibrator 14 to the pressure sensor 20 via the weighted transducer 18. Measurement accuracy is improved.

  In the above, as shown in FIG. 2, the pressure sensor 20 formed by the piezoelectric material 26 and the electrodes 28A and 28B has a cylindrical shape, and the example in which the electrode 28A is in contact with the transducer bottom surface 36 has been described. The shape of the target pressure sensor 20 is not limited to a cylindrical shape. In other words, the pressure sensor 20 may be disposed between the weighted transducer 18 and the sensor base 22 and may have a shape that can be brought into contact with the weighted transducer 18 with a predetermined contact area. If the pressure sensor 20 has a flat surface for contacting the weighted transducer 18 and a flat surface for placing the pressure sensor 20 on the sensor base 22, measurement is easy. Therefore, even if the pressure sensor 20 is housed in a housing (measuring housing having the above two planes) formed for sensor reception sensitivity measurement and disposed between the sensor base 22 and the weighted transducer 18. Good.

  Further, the shape of the weight converter 18 is not limited to that shown in FIG. In other words, the weighting converter 18 may be disposed between the actuator 16 and the pressure sensor 20 and have a shape that can be brought into contact with the pressure sensor 20 with a predetermined contact area. Preferably, the weighted transducer 18 has a flat surface for contacting the pressure sensor 20 or the measurement housing.

  After measuring the sensor receiving sensitivity of the pressure sensor 20 in the above procedure, as shown in FIG. 6, the pressure sensor 20 is a rubber that is acoustically less damped for use in seawater or other media. Housed in a housing 38 formed of a material, plastic resin, or the like. For example, the casing 38 is formed by sealing the pressure sensor 20 with a plastic resin or the like. In the example shown in FIG. 6, the housing 38 has a sensor top surface 40 that contacts the transducer bottom surface 36 and a sensor bottom surface 42 that contacts the sensor base 22. In the case where the housing 38 has a structure for transmitting the vibration from the weighted transducer 18 to the piezoelectric material 26 with low loss, the above method is performed after the piezoelectric sensor 20 is housed in the housing 38. The sensor reception sensitivity may be measured by

  DESCRIPTION OF SYMBOLS 10 Signal generator, 12 Amplifier, 14 Exciter, 16 Actuator, 18 Weighted transducer, 20 Pressure sensor, 22 Sensor stand, 24 Analyzer, 26 Piezoelectric material, 28A, 28B Electrode, 30A, 30B, 34A, 34B Conductor , 32 Weighted protrusion, 36 Converter bottom surface, 38 Housing, 40 Sensor top surface, 42 Sensor bottom surface.

Claims (4)

In a sensor reception sensitivity measuring method for measuring a sensor reception sensitivity indicating a relationship between a sound pressure applied to a pressure sensor and a detection value by the pressure sensor,
Generating vibration by a vibrator, applying vibration to a weighted transducer that detects the magnitude of vibration, and applying vibration to the pressure sensor through the weighted transducer;
Displaying or storing information indicating a detection value by the pressure sensor and information indicating a detection value by the weighted transducer as information for sensor reception sensitivity measurement; and
A sensor reception sensitivity measuring method comprising: In a sensor reception sensitivity measurement system for measuring a sensor reception sensitivity indicating a relationship between a magnitude of sound pressure applied to a pressure sensor and a detection value by the pressure sensor,
An exciter that generates vibration;
A weighting transducer that applies vibration generated from the vibrator to the pressure sensor and detects the magnitude of the vibration;
An analyzer for measuring the sensor receiving sensitivity based on the detection value by the pressure sensor and the detection value by the weighted converter;
A sensor receiving sensitivity measuring system comprising: In the sensor receiving sensitivity measuring system according to claim 2,
The detection value by the weighted transducer has a unit of force,
The analyzer is
In addition to the detection value by the pressure sensor and the detection value by the weighting transducer, the sensor reception sensitivity is measured based on a contact area between the weighting transducer and the pressure sensor. Sensitivity measurement system. In the sensor receiving sensitivity measuring system according to claim 2 or 3,
The vibrator is
Generates vibration with white noise characteristics,
The analyzer is
A frequency analysis unit for performing frequency analysis on the detection value by the pressure sensor and the detection value by the weighted transducer;
A frequency characteristic measurement unit that measures the frequency characteristic of the sensor reception sensitivity based on the frequency analysis;
A sensor receiving sensitivity measuring system comprising:

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