CHAPTER 2. USBOARD-USS5
2.2. OPERATING PRINCIPLE
Warning:
The USBoard-USS5 is no safety system and can only provide supporting, non-safe information. Never
use the USBoard-USS5 for safeguarding of dangerous areas or movements.
2.2.2 Cross Echo Mode
In the traditional, sequential operation mode the sensors are independent from each other. They operate in an infinite
loop one after the other, with each sensor sending its own ultrasonic pulse and waiting for the echo to calculate the
distance to the object (left picture below). If a sensor receives an echo from a pulse that was sent earlier by another
sensor it will be treated like a regular echo, resulting in a faulty measurement (right picture).
In cross-echo mode only one sensor of the group of four will send a pulse but all four sensors can receive the echo. If
the positions of all sensors are known it is possible to estimate the location of the detected object based on the different
durations it takes the echo to reach each sensor.
Several aspects should be kept in mind when calculating the object’s position.
• Depending on the shape and surface of an object the ultrasound pulse is reflected or absorbed differently. This is
why some objects may be detectable with direct measurements in normal mode but do not create a sufficiently
strong cross-echo.
• The realistic field of view of the sensors is rather limited at large distances and also dependent on form and
material of the object. It is thus recommended to do some experiments and tests in cross-echo mode before
setting up the actual application.
• The distance calulation performed by the USBoard-USS5 is the same in both operating modes: The time be-
tween sending and receiving the echo is halved and multiplied with the speed of sound. This reduces processing
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