multiple Ultrasonic sensors (HC-SR04) conflict receiving each other's signals

Other Hardware Sensors
1

Hello,

I'm new in this forum and this is my first post but i'm a little experienced with using Arduino boards.

I'm designing a system that uses multiple Ultrasonic distance measurement sensors (HC-SR04), each sensor is working fine and accurate when i'm testing them alone. The problem is when i run them together, the echo signal of one of the sensors is not accurate (nearly %40 less than the actual distance of the obstacle).

My questions are:

1 - Are the sensors generating the same signal frequency?
2 - Are they receiving each other's echo signal or each one receives its own echo?

Thank you for the help.

2

1-yes, 40 kHz. There is no way to change that.
2-yes, they interfere with each other. You have to fire each sensor individually, and wait for its response before you fire another one.

3

1-yes, 40 kHz. There is no way to change that.
2-yes, they interfere with each other. You have to fire each sensor individually, and wait for its response before you fire another one.

Thank you for your help, now they're working fine.