Pepperl+Fuchs’ ultrasonic sensors determine the distance to an object using the echo transit time method. The measured distance can be evaluated and displayed in different ways. The distance to the object is converted into an analog value and displayed at the analog output (for example, 0-10 V, 4-20 mA) of the ultrasonic sensor. Alternatively, the object distance can be directly transmitted to a controller as a digital value via a special interface like IO-Link.
For ultrasonic sensors with switching outputs, the output state changes when an object is detected within the set switching range. A distinction is also made between NO and NC functions, depending on the response to the object.
For sensors with switching outputs, the following different operating modes can be set using an appropriate assembly and parameterization.
Ultrasonic sensors are most commonly used in diffuse mode. The emitter and receiver are located in the same housing. The target acts as a sound reflector.
In retroreflective mode, a permanently installed reflector constantly reflects the ultrasonic signal. An aligned metal or plastic panel can be used as a reflector. An existing background such as a wall, conveyor belt, or the floor can also be used. As long as there is no object between the ultrasonic sensor and the reference reflector, the sensor receives a constant echo from the reflector. When a detected object enters the detection range, the reflection of the ultrasound signal changes and the ultrasonic sensor detects the presence of the object. In general, the following three scenarios trigger switching.
All three scenarios trigger switching at the ultrasonic sensor output. Retroreflective sensors are especially recommended for reliable detection of sound-absorbing objects. They are also suitable for objects without reliably detectable surfaces, e.g. smooth, slanted surfaces such as a car windshield. There are no blind zones in this operating mode.
Ultrasonic thru-beam sensors use dedicated emitter and receiver transducers that are contained in two separate housings. The evaluation electronics and outputs are housed with the receiver. The ultrasonic sensors are mounted opposite one another on a common axis. When an object interrupts the sound beam, the sensor switching output is activated. The receiver sensitivity can usually be set (Teach-In, potentiometer) for different intervals between the emitter and receiver and/or for different object sizes. This mode is extremely resistant to external disturbances. It also doubles the range and enables objects to be reliably detected at significantly greater distances. The switching frequency is considerably faster, as the ultrasonic sensor does not have to continuously switch between transmission and reception modes.