PDC Sensor for Machine Safety - Safety-Rated Ultrasonic Proximity Sensing for Personnel Protection in Industrial Automation
This technical article explores the safety-rated ultrasonic proximity sensing for personnel protection in industrial automation, covering the safety certification requirements, the ultrasonic sensing principles for three-dimensional protection, the sensor configuration for various machine types, and the integration with industrial control systems for comprehensive personnel safety.
Safety-rated ultrasonic proximity sensing provides personnel protection in industrial automation by detecting the presence of people in hazardous areas around machinery. The USi-safety ultrasonic sensor system is certified according to EN ISO 13849 category 3 PL d, making it suitable for use in safety applications where personnel protection is required. The system uses ultrasonic technology to detect people and objects in a three-dimensional space, providing a protective field that covers the hazard area. The sensor's elliptical sound field has an opening angle of ±17° and ±5°, optimized for monitoring a 3-D range and detecting obstacles that hang from above or are raised off the ground. The sensor units are extremely small and can be freely positioned, enabling installation in confined spaces where other safety sensors cannot fit. The system's ability to detect objects made of different materials reliably, combined with its resistance to environmental influences, makes it suitable for a wide range of industrial applications.
PDC Sensor
The safety certification requirements for ultrasonic machine safety sensors are stringent. The sensor must meet EN ISO 13849 category 3 PL d, which requires a high level of reliability and fault tolerance. The system must provide redundant safety outputs (OSSD) that are short-circuit and cross-circuit monitored, ensuring fail-safe operation. The sensor's reaction time must be fast enough to stop the machine before a person can enter the danger zone, typically within 99 ms. The sensor must operate reliably in the presence of environmental influences such as dirt, temperature, air flow, and humidity, which can affect the performance of other sensing technologies. The safety certification ensures that the sensor provides the required level of protection for personnel in industrial environments.
The ultrasonic sensing principles for three-dimensional protection enable comprehensive coverage of the hazard area. The sensor emits ultrasonic pulses and measures the echo return time to detect objects in the protection field. The elliptical sound field provides coverage in both horizontal and vertical directions, detecting objects regardless of their position or orientation. The sensor's ability to detect moving and stationary objects with any shape, color, or surface ensures that all potential hazards are detected. The teach-in function allows the detection area to be configured for the specific application, with the sensor learning the standard environment and suppressing vehicle contours that could cause disturbance. The three-dimensional protection ensures that personnel are protected regardless of their position relative to the machine, providing comprehensive safety coverage.
The sensor configuration for various machine types adapts to the specific requirements of each application. For robots and automated cells, sensors can be mounted around the work area to detect personnel approaching the robot's workspace. For industrial trucks and AGVs, sensors can be mounted on the vehicle to detect personnel in the vehicle's path. For machinery with large hazard areas, multiple sensors can be deployed to provide comprehensive coverage. The sensors can be configured with different protection field sizes and warning field sizes, with the protection field triggering a machine stop and the warning field providing an early alert to personnel. The sensors can be mounted up to three meters cable length away from the control unit, providing flexibility in sensor placement.
The integration with industrial control systems uses the sensor's safety outputs to control machine operation. The sensor provides two OSSD outputs for the protection field, which are connected to the machine's safety relay or safety PLC. When a person enters the protection field, the OSSD outputs switch to the safe state, triggering an emergency stop or speed reduction of the machine. The sensor also provides a PNP switching output for the warning field, which can be used for warning lights or audible alarms. The sensor's parameterization software enables easy configuration of the protection field and warning field, adapting the sensor to different applications. The integration ensures that personnel are protected from hazardous machinery while maintaining productive operation. The ultrasonic machine safety sensor continues to evolve, providing the safety-rated sensing required for personnel protection in industrial automation.
