Non-contact measurement of distance, position and displacement is a key technology for industrial applications in which the speed of the process, the fragility of the material or the inaccessibility of the measuring point make traditional methods unsuitable. Laser, capacitive, inductive and optical sensors make it possible to acquire thousands of measurements per second on moving surfaces, hot materials, products being processed or delicate objects, eliminating mechanical wear and contact errors.
Would you like help choosing the right product ?
Non-contact measuring principles
The most widespread techniques are: laser triangulation, in which a collimated beam is projected onto the target and the reflected image is acquired by a CMOS/CCD sensor positioned at an angle, the distance being derived from the position of the spot on the array; time-of-flight (ToF), which measures the flight time of a light pulse modulated in phase or in amplitude; laser interferometry for very high resolution measurements; chromatic confocal sensors, which use chromatic dispersion to measure the distance and the thickness of transparent materials; and capacitive and inductive sensors for short-range applications in an industrial environment.
Types of instrument
The section comprises portable laser distance meters for quick measurements on site and in industry, industrial laser distance sensors (triangulation and ToF) for integration into machines and plants, high-resolution position and displacement sensors (capacitive, inductive, eddy current) for precision applications, specialised detectors of holes and discontinuities on moving webs (punch hole detection), and laser lines and levels for alignment and marking out. Each family covers different ranges, resolutions and accuracy classes, according to the sector of use.
Industrial applications
Non-contact sensors are used in the continuous measurement of products in extrusion, rolling, drawing and calendering, in position control of robots and actuators in industrial robotics, in level checking in tanks and hoppers, in the positioning of cranes and industrial trucks, in the predictive maintenance of rotating machines for run-out measurement, and in the detection of point defects on continuous webs (laminates, plastic films, non-woven fabrics). Integrating several sensors allows the three-dimensional reconstruction of complex profiles.
Laser safety and regulations
The use of laser sources is governed by IEC 60825-1, which defines the safety classes (1, 1M, 2, 2M, 3R, 3B, 4) and the protective measures required. Industrial sensors belong predominantly to classes 1 and 2, which are inherently safe. For CE marking and use in classified environments, EN 60204-1 (electrical safety of machinery) applies and, for explosive atmospheres, the ATEX Directive 2014/34/EU. Sensor specifications also follow VDI/VDE 2634 for optical measurement of form and dimension.
Selection criteria
Choosing the right sensor depends on the measuring range, the resolution required, the acquisition bandwidth (Hz/kHz), the characteristics of the surface to be measured (reflectivity, roughness, colour, geometry), the operating environment (temperature, dust, vibration), the output interface (analog, digital, fieldbus) and the safety requirements. In the child pages each technology is examined in more detail, with typical parameters and application guidance.
The selection of a measuring system must take into account the trade-off between precision, speed, complexity of integration and life-cycle cost. A correctly sized system not only reduces scrap and increases productivity, but also generates process data that feeds company analytics systems and enables predictive maintenance strategies. The technological choice should always be validated by a feasibility study on the real sample, including MSA (Measurement System Analysis), Gage R&R and calculation of the expanded uncertainty in accordance with the GUM.
You must be logged in to post a comment.