Ultrasonic Sensors Application guide: Usage and applications

Here we present, as an application guide for ultrasonic sensors, information on the operating principle of distance detection and on the usage and applications of ultrasonic sensors in PAS (parking assist) applications, human detection, double feed detection, and more.
In addition to the above, ultrasonic sensors can be used for applications such as object detection on conveyor belts and obstacle detection in automated robot vacuum cleaners.

Time × speed of sound (approx. 340 m/s) = distance to object (round trip)
The time from the start of transmission until reflected waves are received is measured.

Measures the distance to obstacles (walls, etc.) and reports their proximity to the driver.

Pulse signals are transmitted, the ultrasonic waves reflect off of obstacles, and the distance to the obstacles is measured based on the time until the reflected waves are received.
A clock pulse is generated when each pulse signal is transmitted, and this clock is used to measure the time.
Reflection time (s) × speed of sound (340 m/s) = distance to obstacle (round trip)

• Must be able to detect a wall behind the vehicle while ignoring the curb.
• Each sensor must cover a wide range to reduce the total number of sensors required.
• Must be able to detect very close proximity.

The received signal waveforms are different in the 1st frame and 2nd frame.
⇒　A moving person (object) is present.

Double feed detection is a function used in scanners and printers that determines when two sheets of paper have passed through the paper feed mechanism at the same time. Double feed detection is particularly essential in commercial scanners that are often used to scan important items such as checks or official government documents because it is necessary to prevent multiple sheets from going through the paper feed mechanism at once.

Sound waves are reflected by the paper, lessening radiated waves.

There is no abrasion because mechanical contact is not required.
No adjustment to account for paper thickness or quality is necessary.
Detection is also possible when using transparent sheets.
(The color of the paper has no effect on performance.)

We sometimes receive inquiries regarding the use of Murata products in some applications they are not intended.Murata products are not suitable for the following applications.

Murata products are designed to propagate ultrasonic waves through the air. They are not designed to be used with media such as liquids or solids.

Although automatic door applications can utilize wide-range sensing indoors, this often leads to situations in which the doors open or close after sensing objects other than the intended persons. Nowadays, optical sensors or touch sensors are primarily used for such applications.
Ultrasonic waves are also not suitable for use in automatic hand washers because short-distance detection and drip-proof sensors are required. Optical sensors are used primarily for such applications.

Due to outdoor use, a drip-proof type is needed, but since Murata’s drip-proof type products are for automotive applications only, they cannot be used.

Murata products may not be suitable due to the usage environment or durability requirements. Please contact a Murata sales representative for details.

A drip-proof type would be necessary and transmission- and reception-only sensors would be needed. Since Murata’s drip-proof type products are for automotive applications only and are of the transmission-reception combined type, they cannot be used.