At an iron fabrication plant, two overhead cranes operate on one runway; at times, the manufacturing process requires the cranes to operate in overlapping areas of the bay. If an operator becomes distracted or is concentrating on the load being transported, a collision with the opposing crane is possible.

A complete system using noncontacting ultrasonic sensors for the purpose of material handling system collision avoidance is available from STI. The main advantage of using ultrasonic sensors is price; alternative technologies such as laser sensors can be used, but at twice the price.

The addition of ultrasonic sensors to the cranes provides the operator with an audible warning when one crane comes within 40 ft of the opposing crane. The warning alerts the operator that the cranes are in close proximity. If the operator continues movement toward the opposing crane, the braking system will activate at 10 ft. The DCU-1100 sensor is equipped with specialized filtering to eliminate false tripping due to ambient factory noise. The trip points may also be configured in a fail-safe mode to alert operators of sensor failure.

Proper mounting of the sensor ensures reliable performance and reduces the potential for false echoes. In this application, a mounting clamp is used to mount the sensors. To prevent false echoes caused by cross talk, the sensors are mounted on opposite sides of the crane and are pointed at a portion of the opposing crane that provides a large, flat, smooth surface from which to reflect the ultrasonic pulse. Although nothing can replace a cautious operator, the addition of ultrasonic sensors to the cranes has provided a margin of safety previously not available.

DCU-1100 Self-Contained Ultrasonic Sensors

• Maximum range from 2-50 ft


• Works on solids or liquids


• Analog, digital, and trip point outputs


• AutoSense software available on most sensors


• Easy to install


• Internal temperature compensation available


• Maintenance free


• Many models are serial interface programmable with free software for Windows, DOS, or Palm Operating System.