Ultrasonic Sensor. Application Manual. Cat.No.S15E-5. S15E.pdf Murata Manufacturing Co., Ltd. !Note

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1 This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our!note Ultrasonic Sensor Application Manual Cat.No.SE- Murata Manufacturing Co., Ltd.

2 This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our!note Introduction An ultrasonic sensor transmit ultrasonic waves into the air and detects reflected waves from an object. There are many applications for ultrasonic sensors, such as in intrusion alarm systems, automatic door openers and backup sensors for automobiles. Accompanied by the rapid development of information processing technology, new fields of application, such as factory automation equipment and car electronics, are increasing and should continue to do so. Using its unique piezoelectric ceramics manufacturing technology developed over many years, Murata has developed various types of ultrasonic sensors which are compact and yet have very high performance. The information contained in this catalog will help you to make effective use of our ultrasonic sensors. Features of Murata Ultrasonic Sensor () Compact and light-weight () High sensitivity and high sound pressure () High reliability

3 This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our!note Characteristics of Ultrasonic Waves Y YYYYYYYY0. Wavelength and Radiation...0. Reflection...0. Effects of Temperature...0. Attenuation...0 CONTENTS Construction and Operation PrinciplesY YYYYY0. Open Structure Type Ultrasonic Sensors...0. Enclosed Type Ultrasonic Sensor...0. High Frequency Ultrasonic Sensors...0 Electrical Characteristics Y YYYYYYYYYYYYYYYYYY0 Characteristics of Ultrasonic Waves Construction and Operation Principles. Sound Pressure Characteristics...0. Sensitivity Characteristics...0. Radiation...0. Ratings...06 Electrical Characteristics ApplicationsY YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY08. Examples of Applications Transmitting and Receiving Circuits Applications for Distance Measurement Installation Sharpening of Radiation...0 Environmental TestsY YYYYYYYYYYYYYYYYYYYYYYY 0!Notice...0 Applications Environmental Tests

4 08.0. Characteristics of Ultrasonic Waves Ultrasonic waves are sounds which cannot be heard by humans and are normally, frequencies of above 0kHz. The basic characterisitics of ultrasonic waves are explained below.. Wavelength and Radiation Velocity of wave propagation is expressed by multiplication of frequency and wavelength. The velocity of an electromagnetic wave is 0 8 m/s, but the velocity of sound wave propagation in air is as slow as about m/ s (at 0 C). At these slower velocities, wavelengths are short, meaning that higher resolution of distance and direction can be obtained. Because of the higher resolution, it is possible to get higher measurement made large accuracy. The surface dimension of the ultrasonic device can be easily to obtain accurate radi-ation.. Reflection In order to detect the presence of an object, ultrasonic waves are reflected on objects. Because metal, wood, concrete, glass, rubber and paper, etc. reflect approximately 00% of ultrasonic waves, these objects can be easily detected. Cloth, cotton, wool, etc. are difficult to detect because they absorb ultrasonic waves. It may often be difficult, also, to detect objects having large surface undulation, because of irregular reflection.. Effects of Temperature Velocity of sound wave propagation c is expressed by the following formula. c= t (m/s) where t=temperature ( C) That is as sound velocity varies according to circumfer- ential temperature, it is necessary to verify the temperature at all times to measure the distance to the object accurately.. Attenuation The strength of ultrasonic waves propagated into the air attenuate proportionally with distance. This is caused by diffusion loss on a spherical surface due to diffraction phenomenon and absorption loss, that energy is absorbed by medium. As shown in Fig., the higher the frequency of the ultrasonic wave, the bigger the attenuation rate and the shorter the distance the wave reaches. Attenuation (db) (t= 0ϒC) Frequency -0 0 (khz) 0 (khz) (khz) 00 (khz) Distance (m) Fig. Attenuation Characteristics of Sound Pressure by Distance

5 08.0. Construction and Operation Principles When voltage is applied to piezoelectric ceramics, mechanical distortion is generated according to the voltage and frequency. On the other hand, when vibration is applied to piezoelectric ceramics, an electric charge is produced. By applying this principle, when an electric signal is added to a vibrator, constructed of sheets of piezoelectric ceramics or a sheet of piezoelectric ceramics and a metal sheet, an electric signal is radiated by flexure vibration. As a reverse effect, when an ultrasonic vibration is added to the vibrator, an electric signal is produced. Because of these effects, piezoelectric ceramics are utilized as ultrasonic sensors.. Open Structure Type Ultrasonic Sensors As shown in the diagram of an ultrasonic sensor (Fig. ), a multiple vibrator is fixed elastically to the base. This multiple vibrator is a combination of a resonator and a vibrator which is composed of a metal sheet and a piezoelectric ceramics sheet. The resonator is conical in order to efficiently radiate the ultrasonic waves generated by the vibration and also in order to effectively concentrate the ultrasonic waves at the central part of the vibrator. Fig. shows a finite element method simulation of the vibration of the multiple vibrators. Case Horn Metal Plate Piezoelectric Ceramics Base Lead Terminal Fig. Construction of Open Structure Type Ultrasonic Sensor Cross Section of Half Side Fig. Simulation of Vibration

6 08.0. Construction and Operation Principles. Enclosed type Ultrasonic Sensor Ultrasonic sensors for outdoors use are sealed to protect them from dew, rain and dust. Piezoelectric ceramics are attached to the top inside of the metal case. The entrance of the case is covered with resin. (See Fig..) Metal Case Piezoelectric Ceramic Lead Wire Base Shielding Material Cable Fig. Construction of Enclosed Type Ultrasonic Sensor. High Frequency Ultrasonic Sensors For use in industrial robots, accuracy as precise as mm and acute radiation are required. By flexure vibration of the conventional vibrator, no practical characteristics can be obtained in frequencies higher than 70kHz and, therefore, vertical thickness vibration mode of piezoelectric ceramics is utilized for detection in high frequency. In this case, the matching of acoustic impedances of the piezoelectric ceramics and air becomes important. Acoustic impedance of piezoelectric ceramics is.6 0.7kg/m s, while that of air is. 0.kg/m s. This difference of powers causes large loss on the vibra-tion radiating surface of the piezoelectric ceramics. Matching the acoustic impedances with air is performed by bonding a special material to the piezoelectric ceramics as an acoustic matching layer. This construction enables the ultrasonic sensor to work in frequencies of up to several hundred khz. Ultrasonic Radiation Surface Acoustic Matching Layer Piezoelectric Ceramics Metal Case Base Shielding Material Lead Terminal Fig. Construction of High Frequency Ultrasonic Sensors

7 08.0. Electrical Characteristics. Sound Pressure Characteristics Sound pressure level (S.P.L.) is unit indicating the volume of sound and is expressed by the following formula. S.P.L.=0log P (db) Po where P is Sensor sound pressure (Pa) and Po is reference sound pressure (0µPa). Fig.6 shows a sound pressure measuring circuit.. Sencitivity Characteristics OSC. F.C. U.S. 0cm S.C.M. Anechoic Room Amp. U.S. : Ultrasonic Sensor S.C.M. : Standard Capacitor Microphone (Brüel & Kjær ) Amp. : Amplifier (Brüel & Kjær 60) Input Voltage : 0Vrms, Sine wave F.C. : Frequency Counter 0dB=0µPa Fig. 6 Sound Pressure Measuring Circuit Sensitivity is the unit indicating the sound receiving level and is expressed by the following formula. Sensitivity=0log S (db) So where S is Sensor voltage (V) and So is reference sound pressure (V/Pa). Fig.7 shows a sensitivity measuring circuit. The.9kΩ resistor connected with the electrode terminal of the sensor is used to avoid the influence of outside noise. OSC. Sp S.C.M. Amp. U.S. 0cm RL F.C. Anechoic Room RL :.9kΩ U.S. : Ultrasonic Sensor S.C.M. : Standard Capacitor Microphone (Brüel & Kjær ) Amp. : Amplifier (Brüel & Kjær 60) OSC. : Oscillator Sp. : Tweeter F.C. : Frequency Counter 0dB=0V/Pa Fig. 7 Sensitivity Measuring Circuit. Radiation The ultrasonic sensor is installed on a table. Then, the relationship between angle and sound pressure (sensitivity) is measured. In order to express radiation precisely, the angle in which the sound pressure (sensitivity) level attenuates by 6dB compared with the front is called the half attenuation angle with an expression of θ /.

8 08.0. Electrical Characteristics. Ratings The ratings and dimensions of representative types of these ultrasonic sensors appear in Table. Also frequency characteristics of sensitivity and sound pressure are shown in Figs. 8 and 9 and their radiation characteristics Figs. 0 and. Part Number Item Construction Using Method MA0SR/S Open structure type Receiver and Transmitter (Dual use) type Nominal Frequency (khz) 0 Overall Sensitivity (db) Sensitivity (db) 6± Sound Pressure (db) 0± Directivity (deg) 80 Capacitance (pf) 0±0% Operating Temperature Range ( C) Detectable Range (m) 0. - Dimension (mm) ø9.9 7.h Weight (g) 0.7 Max. Input Voltage 0 Vp-p Square wave 0kHz Part Number Item MA0E7R/S MA0E8- MA0MF-B Construction Water proof type Using Method Receiver and Transmitter type Combined use type Nominal Frequency (khz) 0 Overall Sensitivity (db) Sensitivity (db) 7 min. 8 min. 87 min. Sound Pressure (db) 06 min. 0 min. Directivity (deg) Capacitance (pf) 00±0% Operating Temperature Range ( C) Detectable Range (m) Dimension (mm) ø8 h ø 8h ø 9h Weight (g).. 00 Vp-p 60 Vp-p Max. Input Voltage Square waves 0kHz Square waves 0kHz Pulse width 0. ms Pulse width 0.8ms Interval 00 ms Interval 60 ms Distance : 0cm, Sensitivity : 0dB=0V/Pa, Sound pressure Level : 0dB=0µPa. The sensor can be used in the operating temperature range. Please refer to the individual specification for the temperature drift of Sensitivity/Sound pressure level or environmental characteristics in that temperature range. Directivity, and Detectable Range typical is value. It can be changed by application circuit and fixing method of the sensor. 6

9 08.0. Electrical Characteristics Item Part Number MA80A MA00A MA00A Construction High frequency type Using Method Combined use type Center Frequency (khz) 7± 00±0 00±0 Overall Sensitivity (db) -7 min. 0dB=8Vpp (at 0 cm) - min. 0dB=8Vpp (at 0 cm) Directivity (deg) 7-7 min. 0dB=8Vpp (at 0 cm) Operating Temperature Range ( C) Detectable Range (m) Dimension (mm) ø7.h ø9 0.6h ø 0.h Weight (g) 9 6 Max. Input Voltage 0 Vp-p Square waves 7kHz Pulse width 600µs Interval 0 ms 0 Vp-p Square waves 00kHz Pulse width 0µs Interval 0 ms 0 Vp-p Square waves 00kHz Pulse width µs Interval 0 ms The sensor can be used in the operating temperature range. Please refer to the individual specification for the temperature drift of Sensitivity/ Sound pressure level or environmental characteristics in that temperature range. Directivity, and Detectable Range is typical value. It can be changed by application circuit and fixing method of the sensor. Sensitivity (db) RL=.9kΩ 0dB=0V/Pa MA0SR MA0E7R Sound Pressure Level (db) Distance 0cm Input Voltage 0Vrms (Sine Wave) 0dB=0µPa MA0SS MA0E7S Frequency (khz) Fig. 8 Sensitivity Frequency (khz) Fig. 9 Sound Pressure Frequency 0kHz Distance 0cm Frequency 0kHz Input Voltage 0Vrms (Sine Wave) Distance 0cm 60 0 Attenuation (db) MA0E7R MA0SR 60 0 Attenuation (db) MA0E7S MA0SS Fig. 0 Radiation Characteristics (Receiver) Fig. Radiation Characteristics (Transmitter) 7

10 08.0. Applications. Examples of Applications Ultrasonic sensors are utilized for many purposes such as measurement applications etc. For examples of these applications, please refer to the examples in Table and the explanations as follows. Level detection of continuous wave signals (Example ) is used for counting machines and approximate switches due to the simple circuit construction of these devices. Example is used in devices such as automatic doors where the environment is very changeable. The system is arranged so that the instrument may actuate only when a certain number of reflected pulses is detected. And example is also used for measuring distance to an object, such as the back up sensors of cars. No. Function Method Example is an application utilizing the phenomenon by which the Doppler effect produces a modulated signal as an object moves closer or farther away. This is often used for intruder alarm systems. Example is an application utilizing the change of sound velocity according to the density and the flow speed of a gas. Example is a method used to count the number of Karman vortex generated against flow speed and utilize phenomena that ultrasonic signals level are reduced as Karman vortex passes into the sensor. -S : transmitter Performance Principle ( -R : receiver ) Applications Input Signal Detection of Signal level of continuous wave Output Signal S R Object Counting instruments Access switches Parking meters Input Signal Measurement of pulse reflection time T Output Signal S R Object Automatic doors Level gauges Automatic change-overs of traffic signals Back sonars of automobiles Input Signal S Utilization of Doppler effect Output Signal R Object Movement Intruder alarm systems Input Signal Measurement of direct propagation time S R T Output Signal Densitometers Flowmeters Obstacle S Input Signal Measurement of Karman vortex Flowmeters R Output Signal Table Application Examples 8

11 08.0. Applications. Transmitting and Receiving Circuits Examples of transmitting and receiving circuits using MA0SR/S are shown in Figs. to. By changing a part of the constants, they can be applied for other purposes. Fig. is a simple circuit using a C-MOS IC and is used for continuously transmitting ultrasonic waves. Fig. is a pre-amp circuit that amplifies the ultrasonic receiving signal. Fig. is an ultrasonic pulse transmitting circuit. Vcc=V Id=mA k Rf 0k Freq.=0kHz p 0 09B (Vc:p) (GND:8P) Ultrasonic Sensor (Transmitter) k 8 000p 6 Out put + Gain=dB 7Vp-p GND Ultrasonic Sensor (Receiver) 0 + Fig. Example of Continuous Wave Transmitting Circuit Fig. Example of Receiving Circuit 0k.M Vcc=V Id=mA Timming Pulse Out k 6 0B (Vc:p) (GND:7P) 60p 9 09B (Vc:p) (GND:8P) 0 0Vp-p Ultrasonic Sensor (Transmitter) GND Freq.=0kHz ms 0kHz ms Fig. Example of Pulse Transmitting Circuit 9

12 08.0. Applications. Applications for Distance Measurement Fig. shows the principles of measuring distance and is called the "pulse reflection method" which makes it possible to count the number of reference pulses. This method is used to measure reflection time up to the object between transmitting pulse and receiving pulse of the ultrasonic wave. The relationship between the distance up to the object L and the reflecting time T is expressed by the following formula : L=C T/ where C is the velocity of sound. That is, the distance to the object can be ascertained by measuring the reflection time involved in reaching the object. Fig.6 shows an example of a distance measuring circuit using MA0SR/S. Control Circuit Counter Circuit Pulse- Transmission Circuit Receiving Circuit Reflection Time : T Standard Oscillation Circuit Ultrasonic Sensor (Transmitter) Ultrasonic Sensor (Receiver) Distance : L Fig. Principles of Measuring Distance Object 0.0μ TP MA0SS k 0.0μ.9k MA0SR 0μ 0.μ TP B (Vc:p) (GND:8p) Rf p 000p Transmitting Pulse 0B (Vc:p) (GND:7p) Timing Pulse N60 S88 6 0k Freq.=0kHz TP M 000p 0.0μ + 8 TP 7 7k 8 0k 0.0μ 6 6 0k 0.0μ 0.0μ 0.0μ 0k 6 TP 069UB Freq.=7kHz Vcc=V S88 S88 0k 0k 069UB 0B 0p 8 TLR μ TC TC0P 8 k k k k 7 cm SC9 SC9 0Vp-p 0kHz ms ms GND SC9 Fig. 6 Example of Distance Measuring Circuit 0

13 08.0. Applications Fig. 7 shows the wave forms of each part of a circuit. This figure is the result of measuring distance to a flat board (0cm 0cm) located 0cm in front of the ultrasonic sensor mounted on a PC board with transmitter and receiver cm away from each other. If the distance between the transmitter and the receiver is too close, the ultrasonic waves may reach the receiver directly from the transmitter. As shown in Fig. 7 (b), comparison will be made with the comparative voltages that attenuate exponentially with time. Detected reflection wave is shown in Fig. 7 (c). Measuring Point in Fig. 6 TP TP 0V/div 0mV/div Direct Wave Reflection Wave ms/div (a) Transmit/Receive Wave Form Measuring Point in Fig. 6 Measuring Point in Fig. 6 TP V/div TP 0V/div TP V/div TP 0V/div ms/div (b) Receive Circuit Output Voltage (b) and Comparable Voltage Wave form ms/div (c) Comparable Circuit Output Wave Form Fig. 7 Wave Forms of Each Part of Circuit. Installation Fig. 8 is an example of the installation of an ultrasonic sensor. The housing of the ultrasonic sensor should be protected with elastic material, such as rubber, sponge, etc., and care should be taken so that ultrasonic vibration is not transmitted directly to the receiver from the transmitter. Ultrasonic Vibration Transmitter Receiver (a) Bad Example Holder P.W. Board Transmitter Receiver (b) Good Example Holder P.W. Board Elastic material (Ex. rubber, sponge) Fig. 8 Example of Installation of Ultrasonic Sensor

14 08.0. Applications. Sharpening of Radiation When there are objects within the sensors field that reflect ultrasonic waves but when only a specific object should be detected, more acute radiation of ultrasonic waves is advantageous. Radiation is determined by the dimensions of the ultrasonic radiation surface and the frequency, but it is possible to make radiation more 60 acute and measuring distance longer by mounting a horn on the outside of the ultrasonic sensor. Regarding this horn, in general, the wider the diameter of its opening and the longer its total length, the more acute the radiation. The relationship between the configuration of the horn using MA0SR/S and the radiation characteristics is shown in Figs. 9 and 0. A similar result can be obtained regarding sound pressure radiation. θ=0 d 0 d=ø0 l Attenuation (db) θ D l=0 l=0 l=0 0 Sensor only R (mm) D (mm) 7 60 θ / (deg) θ / : Half attenuation angle Fig. 9 Horn Length and Radiation (MA0SR) 0 θ =0 θ =0 θ = Attenuation (db) Sensor only 60 d d=ø0 l=0mm l θ D θ (deg) D (mm) θ / (deg) Fig. 0 Horn Angle and Radiation (MA0SR)

15 08.0. Environmental Tests Environmental tests of MA0SR/S as an example are shown in below.!environmental tests No. Kind of Test Conditions Judgement Humidity Resistance 60 C, - 9%RH, 00 hours High Temperature Storage 8 C, 00 hours Low Temperature Storage -0 C, 00 hours Thermal Shock Vibration 6 Solder Heart Resistance With -0 C (0 minutes) and +8 C (0 minutes) as one cycle, 00 cycles. (Resistance of.9kω connected between terminals of sensor.) Maximum Amplitude :.mm Vibrating cycle : minute Vibrating frequency : 0 - Hz hours in each of directions Soldering terminal up to mm below base at 0 C with soldering tip for seconds. Variation of sensitivity and S.P.L. is within db. 7 Operating Frequency 0kHz, Sine Vp-p, 000 hours Variation of S.P.L. is within 6dB.

16 08.0.!Caution in use. (Notice in design) ) The transducer may generate surge voltage by mechanical or thermal shock. ) Please do not apply D.C.voltage for ultrasonic transducer to avoid migration. ) Please do not use this ultrasonic sensor in water.. (Notice in handling and storage) ) Please do not apply an excessve mechanical shock for this ultrasonic transducer. Please do not apply excessive force on the top of this ultrasonic transducer and terminal pins. ) The products should not be used or stored in a corrosive atmosphere, especially where chloride gas, sulfide gas, acid, alkali, salt or the like are present. Store the products in the room where is normal temperature and humidity, and avoid the sunlight, sudden changes in temperature and humidity. It may cause of failure or malfunction in such conditions. ) Please do not use and storage this ultrasonic sensor in hevy dust and high humidity condition. Store the products where the temperature and relative humidity do not exceed -0 to 0 degrees centigrade, and to 9%RH. Use the products within 6 months after receiving.. (Notice in mounting) ) Please do not apply excessive force for terminals, when soldering. ) Use soldering iron to mount. Don't exceed 0 degc, second. Soldering point should be more than mm below from the bottom of ultrasonic transducer body. ) Please do not clean by water and dissolvent.

17 This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our!note