- General Details
In industrial applications, ultrasonic sensors are characterized by their reliability and outstanding versatility. Ultrasonic sensors can be used to solve even the most complex tasks involving object detection or level measurement with millimetre precision, because their measuring method works reliably under almost all conditions.
No other measuring method can be successfully put to use on such a wide scale and in so many different applications. The devices are extremely robust, making them suitable for even the toughest conditions. The sensor surface cleans itself through vibration, and that is not the only reason why the sensor is insensitive to dirt. The physical principle—the propagation of sound—works, with a few exceptions, in practically any environment.
The measuring method employed by ultrasonic sensors has been viewed as an excessively complex technology, and only used as a “last resort” … as a solution for particularly difficult applications. Those times have long since passed!
Ultrasonic sensors have proven their reliability and endurance in virtually all industrial sectors.
These sectors include:
- Mechanical engineering/machine tool
- Food and beverage
- Woodworking and furniture
- Building materials
- Pulp and paper
- Material handling
- Level measurement
- Thru-Beam Sensors
Ultrasonic thru-beam sensors are always comprised of two separate components: the emitter and the receiver. The evaluation and switching output electronics are located in the receiver.
The emitter and receiver are mounted directly opposite one another. As soon as an object interrupts the sound beam between the emitter and the receiver, the sensor switching output activates.
The receiver sensitivity can be adjusted for different distances between the emitter and receiver, and/or for different object sizes, via Teach-in or a potentiometer.
- Diffuse and Retroreflective Mode 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
- Double Sheet Sensors
The “double sheet control” application originally comes from the printing industry. Here, the appearance of a double sheet or a splice in the paper must be quickly and reliably detected. As the sheet runs between the opposing emitter and receiver, the sensors continuously monitor the status of the entire length. Due to their special design, double sheet sensors are ideal for the following applications:
- Identifying multiple feeds of
Plastics (i.e., vinyl)
- Label detection
- Splice detection
Double sheet sensors are ideal for distinguishing between the following:
- Air/one sheet/two+ sheets
- Air/backing material/backing material with label applied
- Air/single layer of material/two layers of material stuck together
- Air/single plate/two or more plates (i.e., sheet metal)
- Thin papers with a density of 10 g/m² up to cardboard with a density of 2000 g/m² can be monitored
- Detection of thin plastic or metal films
- Customized Teach-in of various materials
- Suitable for use on shiny and transparent materials
- Automatic adjustment of the switching thresholds to changing ambient conditions
- Very high processing speed
- Insensitive to dust and dirt
- Printing press applications, where the ultrasonic double sheet control protects the complex mechanics from being destroyed by preventing two sheets from being pulled in, or identifies a sheet lodged in the machine
- The control of adhesive films in labeling machines, including label counting
- Letter-opening devices, where the opened letters are checked to ensure they have been fully emptied
- Receipt-counting machines
- Packaging machines, where splices identify the start of a new sheet and end of the old one
- The detection of gaps, single sheets, and double sheets in paper processing machinery
- Identifying multiple feeds of