Ultrasonic Sensor: Application Manual
Ultrasonic Sensor: Application Manual
Ultrasonic Sensor: Application Manual
. Therefore, its specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our
sales representatives or product engineers before ordering. This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering.
S15E.pdf 08.10.31
Ultrasonic Sensor
Application Manual
Cat.No.S15E-5
!Note This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, its specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our
sales representatives or product engineers before ordering. This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering.
S15E.pdf 08.10.31
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 (2) High sensitivity and high sound pressure (3) High reliability
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sales representatives or product engineers before ordering. This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering.
S15E.pdf 08.10.31
CONTENTS
1 2 3 4 5
4 ApplicationsY YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY08
1. Examples of Applications .......................................................... 08 2. Transmitting and Receiving Circuits ........................................ 09 3. Applications for Distance Measurement ................................ 00 4. Installation ................................................................................. 0 5. Sharpening of Radiation .......................................................... 02
Applications
Environmental Tests
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Ultrasonic waves are sounds which cannot be heard by humans and are normally, frequencies of above 20kHz. The basic characterisitics of ultrasonic waves are explained below.
2. 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.
3. Effects of Temperature
Velocity of sound wave propagation c is expressed by the following formula. c=33.5+0.607t (m/s) where t=temperature (C) That is as sound velocity varies according to circumferential temperature, it is necessary to verify the temperature at all times to measure the distance to the object accurately.
4. 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.
(t= 20 C) -10
Attenuation (dB)
-30
-40
-50
-60 0.1
Frequency
-20
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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 2 sheets of piezoelec-
Case Horn
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Metal Case
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Electrical Characteristics
U.S.
: Ultrasonic Sensor : Standard Capacitor Microphone : Amplifier : 10Vrms, Sine wave : Frequency Counter
2. Sencitivity Characteristics
Sensitivity is the unit indicating the sound receiving level and is expressed by the following formula. S Sensitivity=20log (dB) So where S is Sensor voltage (V) and So is reference sound pressure (V/Pa) . Fig.7 shows a sensitivity measuring circuit. The 3.9k resistor connected with the electrode terminal of the sensor is used to avoid the influence of outside noise.
OSC. Sp S.C.M. U.S. 30cm F.C. Anechoic Room Amp.
RL
: 3.9k : Ultrasonic Sensor : Standard Capacitor Microphone : Amplifier : Oscillator : Tweeter : Frequency Counter
0dB=10V/Pa
3. 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 /2.
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Electrical Characteristics
4. Ratings
The ratings and dimensions of representative types of these ultrasonic sensors appear in Table . Also frequency characteristics of sensitivity and sound pressure are
Part Number Item Construction Using Method
shown in Figs. 8 and 9 and their radiation characteristics Figs. 0 and .
MA40S4R/S Receiver and Transmitter (Dual use) type Open structure type
Operating Temperature Range (C) Detectable Range Dimension Weight Max. Input Voltage (m) (mm) (g)
Part Number Item Construction Using Method Nominal Frequency Overall Sensitivity Sensitivity Sound Pressure Directivity Capacitance
MA40E8-2
MA40MF14-5B
106 min.
Operating Temperature Range (C) Detectable Range Dimension Weight Max. Input Voltage (m) (mm) (g) 0.2 - 3 1812h 4.5 100 Vp-p Square waves 40kHz Pulse width 0.4 ms Interval 100 ms
30 - +85 148h 0.2 - 1.5 2.4 160 Vp-p Square waves 40kHz Pulse width 0.8ms Interval 60 ms
149h
Distance : 30cm, Sensitivity : 0dB=10V/Pa, Sound pressure Level : 0dB=20Pa. 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.
!Note This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, its specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our
sales representatives or product engineers before ordering. This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering.
S15E.pdf 08.10.31
Electrical Characteristics
Part Number Item Construction Using Method Center Frequency Overall Sensitivity Directivity
MA80A1
MA200A1 High frequency type Combined use type 20010 -54 min. 0dB=18Vpp (at 20 cm) 7
MA400A1
-47 min. 0dB=18Vpp (at 50 cm) -10 - +60 0.5 - 5 4724.5h 93 120 Vp-p Square waves 75kHz Pulse width 600s Interval 50 ms
755
40020
Operating Temperature Range (C) Detectable Range Dimension Weight Max. Input Voltage (m) (mm) (g)
0.2 - 1 1910.6h 6 120 Vp-p Square waves 200kHz Pulse width 250s Interval 20 ms
0.06 - 0.3 1110.5h 2 120 Vp-p Square waves 400kHz Pulse width 125s Interval 10 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.
RL=3.9k 0dB=10V/Pa
MA40S4R MA40E7R Sound Pressure Level (dB)
MA40S4S MA40E7S
30
35
40 Frequency (kHz)
45
50
30
35
40 Frequency (kHz)
45
50
Fig. 8 Sensitivity
Frequency 40kHz Distance 30cm
0 Attenuation (dB) 30 -10 -20 -30 30 MA40E7R MA40S4R 60 60
60
90
90
90
90
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sales representatives or product engineers before ordering. This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering.
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4 Applications
1. 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 2 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 2 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 2 is also used for measuring distance to an object, such as the back up sensors of cars. Example 3 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 4 is an application utilizing the change of sound velocity according to the density and the flow speed of a gas. Example 5 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.
4
No. Function Method Performance Principle
Input Signal
transmitter ( - :: receiver ) S R
Applications
S Object R
Object R
Automatic doors Level gauges Automatic change-overs of traffic signals Back sonars of automobiles
Input Signal S
Object R Movement
R T Output Signal
Densitometers Flowmeters
Obstacle
Input Signal
Flowmeters
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Applications
1k
Rf 100k
+ 4556 4
1000p
Out put
Freq.=40kHz
Gain=32dB
17Vp-p
GND
10
150k
3.3M
Vcc=12V Id=15mA
6 2 0.01 555
8 4 3 14 15
12 13
5 0.01
1 2 100k
5 6
11
12
20Vp-p
30k
560p
GND
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Applications
Control Circuit
Distance : L
4 MA40S4S 0.1 2 10 6 9 7
5 8 11 3 9
10k
5 3 30k
100k
0.01
1S1588
Rf 100k
10k
11 10 11
12 13
15 14 13 12 11 10 9 2 TC5022 3 8 4 5 6
8 4556 4
1000p
4 4069UB 2 3 10k
4011B
TP5 1 100k
220p
15k
15k
Freq.=172kHz GND
0
15k
MA40S4R 10
7 16 11 12 13 14 15 6 TC5051P 10 5 8 4 3 2 0.01
1k7
TP1
Freq.=40kHz
0.01
8 4069UB
TLR3123
cm
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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 (0cm0cm) located 50cm in front of the ultrasonic sensor mounted on a PC board with transmitter and receiver 3cm 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).
TP1
10V/div
TP2
20mV/div
Direct Wave
Reflection Wave
1ms/div
TP3
5V/div
TP1
10V/div 10V/div
TP4
5V/div 1ms/div (b) Receive Circuit Output Voltage (b) and Comparable Voltage Wave form
TP5
4. 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 Holder P.W. Board Transmitter Receiver (a) Bad Example
Holder P.W. Board Transmitter Receiver (b) Good Example Elastic material (Ex. rubber, sponge)
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Applications
5. 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 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 MA40S4R/S and the radiation characteristics is shown in Figs. 9 and 20. A similar result can be obtained regarding sound pressure radiation.
0 30 Attenuation (dB) -10 -20 -30 30 Sensor only 60 =40 =30 =20
60
90
90
d=10 =10
60
90
90
d=10 =30mm
2
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Environmental Tests
Soldering terminal up to 2mm below base at 350C with soldering tip for 3 seconds. Frequency 40kHz, Sine 24Vp-p, 1000 hours Variation of S.P.L. is within 6dB.
3
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!Caution in use
1. (Notice in design) ) The transducer may generate surge voltage by mechanical or thermal shock. 2) Please do not apply D.C.voltage for ultrasonic transducer to avoid migration. 3) Please do not use this ultrasonic sensor in water. 2. (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. 2) 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. 3) 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 40 degrees centigrade, and 5 to 95%RH. Use the products within 6 months after receiving. 3. (Notice in mounting) ) Please do not apply excessive force for terminals, when soldering. 2) Use soldering iron to mount. Don't exceed 350 degC, 3second. Soldering point should be more than 2mm below from the bottom of ultrasonic transducer body. 3) Please do not clean by water and dissolvent.
4
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S15E.pdf 09.8.28