Performance evaluation(1)
of the ultrasonic alarm

Detection range

In the calculation, I make the detection range from 0.4 m to 10 m.

The confirmation of the shortest detection distance

 (1) Set the VR2(For the detection range adjustment) to the clockwise end.(Maximum resistance value) (2) Put the alarm equipment on the about 1 m distance from the obstacle and make the LED lights up. (3) Turn the VR2 counterclockwise until the LED disappears. (4) Bring the alarm equipment close to the obstacle until the LED lights up again.

Repeat (3) and (4). The distance which gets for the LED not to light up is the shortest detection distance.

This time, I could confirm to about 40 cm.

The confirmation of the maximum detection distance

 (1) Set the VR2 in the middle. (2) Put the alarm equipment on the about 1 m distance from the obstacle and make the LED lights up. (3) Separate the alarm equipment from the obstacle gradually until the LED disappears. (4) Turn the VR2 clockwise and make the LED light up again.

Repeat (3) and (4). The distance which gets for the LED not to light up is the maximum detection distance.

The maximum detection distance changes by the output of the ultrasonic, the reception sensitivity, the reflection situation of the obstacle. It is the maximum distance when turning the VR2 to the clockwise end. However, it isn't always possible to detect to the setting distance by the VR2.

This time, I could confirm to about 7m.

Fault of the detection equipment

The ultrasonic alarm equipment detects the ultrasonic that the obstacle is reflected. So, when the reflected wave of the ultrasonic doesn't return to the receiver, it isn't possible to detect.
For example, when the object which has the 45-degree angle is in front of the alarm equipment, it isn't possible to detect.

The detection of the reflected wave of the ultrasonic becomes difficult when making the detection area wide. I think that this is because the reflected wave of the ultrasonic is weak or the ultrasonic which was reflected at the obstacle is reflected in the direction which is different from the receiver.
It is better not to expect this equipment to be highly efficient.