Direct Detection Sensors

With diffuse mode sensors, the runtime of the ultrasonic signal from the sensor to the object is evaluated. Depending on the output stage, the measured object distance is provided either as an analog signal, a binary switching signal, or in digital form via an interface. Software parameterization can be used to set various control modes. As an example, diffuse mode sensors equipped with a switching output can be converted to a retroreflective sensor via PC interface.

In retroreflective mode, the ultrasonic signal is constantly reflected by a permanently installed reflector — the reference reflector.  An aligned metal or plastic panel can be used as a reflector. Or, an existing background such as a wall, conveyor belt, or the floor can be used for this purpose. Any change to the ultrasonic signal caused by an object located between the sensor and reference reflector results in an output change. Such instances may include:

• Additional echoes caused by a small object in front of the reference reflector
• Shorter distances being measured as a result of an object fully concealing the reference reflector
• Loss in echo caused by a highly absorbent object or one with a smooth, angled surface

All of these changes will cause the sensor to switch. In this way, even objects that would otherwise be difficult to sense can be reliably detected.

Features of the diffuse mode / retroreflective sensors from Pepperl+Fuchs include:

• Teach-in function — for quick and simple commissioning
• ULTRA 3000, SONPROG, ULTRA-PROG-IR, and PACTware PC configuration tools — for optimal adaptation of sensors to their application
• Adjustable sound beam width — for optimal adaptation of the sensor characteristics to the relevant application
• Temperature compensation — automatically adjusts for fluctuations in sound velocity as air temperature varies
• Synchronization input — allows sensors to be mounted close together while avoiding mutual interference