Datasheet
10
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S15E.pdf
08.10.31
4
4
Applications
3. Applications for Distance Measurement
Fig.15 shows the principles of measuring distance and is
called the "pulse reflection method" which makes it pos-
sible 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/2 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.16 shows an example of a distance measuring circuit
using MA40S4R/S.
Standard
Oscillation
Circuit
Counter
Circuit
Control
Circuit
Pulse-
Transmission
Circuit
Receiving
Circuit
Object
Reflection Time : T
Distance : L
Ultrasonic Sensor
(Receiver)
Ultrasonic Sensor
(Transmitter)
Fig. 15 Principles of Measuring Distance
GND
40kHz
Transmitting Pulse
1ms
25ms
20Vp-p
1k
Rf
100k
2
3
4
8
1
1000p
2903
4069UB
Timing Pulse
1000p
0.015μ
47k
100k
10k
10k
220p
1N60
1S1588
100k
30k
1M
100k
100k
100k
0.01μ
0.01μ
10μ
3.9k
MA40S4R
TP2
+
+
–
2
3
4
4
3
13
12
0.01μ
0.01μ
11
10
10 169
8 4 5 6
2
3
1112131415
8
TLR312×3
Vcc=12V
cm
11
1
2
8
6
5
1
1 2 3 4
5
6
+
–
10k
15k
15k
15k
10k
1S1588
1S1588
TP1
0.1μ
MA40S4S
4 5
2 3
9
6
5
3
1
1 5
2
6
150k
555
7
8
4
0.01μ
0.01μ
2
4
12
13
15 14
11
8
10 9
6 7
TP3
TP4
TP5
Freq.=172kHz
Freq.=40kHz
560p
4069UB
4011B
TC5022
15
85 4 3 2
1413121116
10
6
7
0.01μ
TC5051P
2SC945
2SC945
2SC945
1k×7
4049B
(Vc:1p)
(GND:8p)
4011B
(Vc:14p)
(GND:7p)
4556
Fig. 16 Example of Distance Measuring Circuit