What are the various classifications and detection principles of fiber optic sensors?

      For fiber-optic sensors, if a through-beam fiber is used, it is a through-beam detection mode; if a direct-inversion fiber is used, it is a proximity detection mode. The ultrasonic sensor is divided into two types of detection modes: through-beam and proximity.

   Detection distance-focus type

      The detection distance of the focus sensor is fixed, that is, its focal length. This requires the sensor to be very close to the measured object.

      The focus sensor can reliably detect the measured object near the focus. This area centered on the focus is called the depth of field. The depth of field depends on the design of the sensor and the reflectance of the measured object. The depth of field of the precision focusing sensor is very small, so it can be used for precise positioning or appearance inspection.

      Sometimes when detecting certain objects, it is necessary to ignore stationary or moving objects in the background. A feature of the focus sensor is that it can ignore objects other than the depth of field. Please note: The near and far points of the depth of field are also affected by the reflectance of the measured object. (Sometimes the sensor does not detect the object with weak reflectance, but it may detect the background with strong reflectance behind the object.)

      Color mark detection is a special application of the focus sensor. The precision focus sensor is used to detect the color mark to locate the product. In color mark detection, the color of the sensor light source is very important, among which the blue-green light source has been proven to have a wider range of use, and it can even detect 20% on white paper Yellow.

      The laser focusing sensor can generate a light spot with a very small energy concentration and a diameter of about 0.25 mm, which is very suitable for detecting small objects or positioning sensors for robots. Due to its strong beam energy, it is often used to detect objects that cannot be reliably detected by other sensors with low reflectance.

   Localized

      The area sensor is a photoelectric proximity sensor, which has a very clear detection range, and can ignore objects outside this range without being affected by the reflectance of the surface of the object.

      The fixed area sensor judges whether the measured object appears by comparing the amount of reflected light falling on the two receivers. If the reflected light falling on the receiver R2 is equal to or more than the reflected light falling on R1, the sensor detects the measured object.

   Adjustable area

      Just like the fixed area type, the adjustable area sensor can distinguish objects located at different distances. In this case, the detection distance is adjustable. The receiver of the adjustable area sensor can generate two currents I1 and I2, and the ratio of these two currents will vary with the position of the reflected light on the receiver. The position of the sensor's cut-off point is directly related to this ratio. The position of the cut-off point can be adjusted by a potentiometer. Even if the object located outside the cut-off point has a strong reflectance, the sensor will still ignore it.

   Fiber optic

      In fact, the optical fiber type is not a specific detection mode, and different detection modes can be formed by using different optical fibers. The use of split optical fiber can form a through-beam detection mode, the use of integrated optical fiber can form a reflective plate or proximity detection mode, special optical fibers can be customized, the optical fiber in the figure below uses a special structure in the detection head to make it Focused detection lens.

   Ultrasonic approach mode

      After the AC voltage is supplied, the ultrasonic generator generates vibration. This vibration alternately compresses and hits air molecules to continuously transmit ultrasonic waves outwards. At the same time, the ultrasonic generator can also receive echoes of ultrasonic waves.

      Ultrasonic sensors are divided into electrostatic and piezoelectric according to their generators.                    Electrostatic sensors are used for long-distance detection, which can usually reach 6-7 meters. This long-distance sensor is often used to detect the liquid level of large containers. Piezoelectric sensors usually have a short detection distance, usually around 1 meter, but they are well sealed and can be used in harsh environments.

      Compared with direct-type photoelectric sensors, ultrasonic sensors are generally less affected by the surface characteristics of the measured object. However, the parallelism between the surface of the ultrasonic generator and the surface of the smooth and flat object must be kept within 3 ° (for rough objects, this angle is not important). Surface-absorbing materials, such as clothing or foam, are difficult to detect using ultrasonic sensors.

      At the same time, the energy of the wave reflected by smaller objects is very weak, so when selecting a sensor, the size of the measured object is a very important factor to be considered. When the object to be measured moves along a plane perpendicular to the sensor detection, ultrasonic sensors have high repeat accuracy, so they are widely used to measure distance.

      Some sensors have an adjustable detection window or analog output that can output a voltage / current value that is proportional to the distance to be measured. The digital filter can make the sensor have the ability to resist electromagnetic or other sound wave interference, the analog output has a high linearity, and the sensor with temperature compensation is suitable for the occasion where the ambient temperature changes greatly.

      In the ultrasonic proximity sensor, there are also products in which the ultrasonic generator is separated from the controller. These small ultrasonic generators can be installed in a small space and detected and output controlled by a controller. Through-beam ultrasonic sensors have independent transmitters and receivers, making them ideal for detecting transparent objects.

If you want to know more, our website has product specifications for fiber optic sensors， you can go to ALLICDATA ELECTRONICS LIMITED to get more information