From MobileRobots Research and Academic Customer Support
The sonar ultrasonic range sensors on Pioneer 3, AmigoBot, PeopleBot and Powerbot are Senscomp series 600 transducers and custom electronics. Sonar range data are calculated by the robot controller and sent by the robot controller firmware to ARIA in the SIP packet every 100ms. See the ARIA documentation for information on reading these data.
On the Pioneer, Peoplebot and AmigoBot, the maximum range of the sonar sensors is 5 meters. If no return signal is received by the sonar, then a value of 5000 mm is provided by the robot controller firmware. The effective minimum range is approximately 200 mm. Sonar transmissions are triggered on each sonar transceiver sequentially to avoid crosstalk. This pattern and its timing (which can affect maximum range) can be adjusted by reconfiguring the robot firmware. The sensitivity of the sonar receiver can also be adjusted via a potentiometer inside the robot, see robot manual for details.
Technical details of the sonar transceivers are available here:
The sonar on Pioneer LX are different sensors, and communication to the sonar system is performed separately than the robot connection (the sonar section of the robot SIP will be empty). Contact support for more information.