Figure 2 shows the distance (e’t) within which the unit senses the target as well
as the distance (e”t) outside of which disturbing objects do not disturb the
operation of the unit. Units with the same frequency may mutually disturb each
other as sent or reflected ultrasound may reach the other unit. To avoid such
interference, units with parallel axes should be installed outside of the minimum
distances as per Figure 3. Greater minimum distances might be required for
applications with targets with round reflecting surfaces (like pipes) that involve
side reflections