Feature: Sensors
Profile thickness measurement (image above) 2D/3D laser profile measurement is used for various applications; e.g., the completeness of weld seams, the optimum dosage of adhesives, or the correct gap dimensions. For the inspection of adhesive beads and applied sealants, laser profile scanners check the presence and size of the beads.
Laser triangulation sensors (image above) Laser triangulation sensors project a red or blue laser beam onto a surface. Te light reflected from the spot is imaged by an optical system onto a position-sensitive element in the sensor. If the sensor or measured object are moved toward the laser beam, the laser sensor determines the correlating distance change. Te sensor controller conditions the distance signal and outputs the measured values via interfaces. Laser triangulation sensors are mostly material-agnostic,
allowing them to measure a wide range of different materials. As laser triangulation sensors are not affected by electrical or magnetic surface properties, almost any material can be measured – including food, metal, plastics, wood, silicon, rubber, and more. Measurement methods can be one- or two-sided.
ThruBeam measurement (image above) With the TruBeam principle, the transmitter of a laser micrometer produces a parallel light curtain that is transmitted via a lens arrangement into the receiving unit. Te beam is interrupted by the object to be measured. Te shadowing generated by this object is recorded by the receiving optical system and output as a value. Parameters such as diameter, gap, height and position can be measured in this way.
Confocal chromatic sensors With confocal chromatic measurements, polychromatic white light is focused onto a target surface by a multi-lens optical system. Te lenses are arranged so the white light is dispersed into monochromatic wavelengths by controlled chromatic aberration. To each wavelength, a specific distance is assigned by factory calibration. Only the wavelength that is exactly focused on the target is used for the measurement. An optical arrangement images the reflected light onto a light-
sensitive sensor element, on which the spectral colour is detected and evaluated. In the case of multi-peak measurements, several distance points are evaluated accordingly. Measurements can be made on practically all types of surfaces, including mirrors and glass. Measurement methods can be one-sided thickness measurement
of transparent materials, two-sided, or multi-layer (e.g., coatings, solar cells, photo masks, smartphone screens).
A combination of technologies (image above) Combining technologies, for example Eddy current and capacitive or Eddy current and TruBeam enable single-sided measurements. Te complementing technologies detect one or other of the material or base surface, and when the values are combinedw give the thickness.
Measurement technologies Here follow some measurement technologies:
Capacitive sensor technology Te principle of capacitive displacement measurement using the capaNCDT (capacitive Non-Contact Displacement Transducer) system is based on the operation of an ideal plate-type capacitor. Te two plate electrodes are represented by the sensor and the opposing measurement object. If a constant alternating current flows through the sensor capacitor, the amplitude of the alternating voltage on the sensor is proportional to the distance
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