In industrial production, distance, diameter and thickness measurement play a central role. Whether it is the quality assurance of round parts, the monitoring of production steps or process control – measuring sensor technology provides the basis for reproducible results. But how can precise measurements be achieved when surfaces are rotating, rough or changeable? And how does thickness measurement actually work with a laser distance sensor? This article provides answers to these questions.
Thickness measurement with laser distance sensors is based on recording two distance values on opposite sides of an object and calculating the difference from this. In contrast to classic methods with tactile measuring heads, optical measurement offers several advantages:
In practice, two sensors are positioned so that they each illuminate one side of the object. The distance values are subtracted in the control system and output directly as material thickness.
This includes applications such as:
Laser triangulation sensors are a special form of laser distance measurement. They work according to the angular principle: a laser beam hits the surface, and a receiver detector determines the distance via the position of the reflection. This principle is ideal for:
In contrast to simple time-of-flight sensors (time-of-flight measurement), triangulation delivers higher precision – ideal for thickness and diameter calculations in the tenths to hundredths of a millimeter range.
In rotating applications, such as the inspection of turned parts, the movement of the object does not have a negative effect, but often a positive one. When the workpiece rotates, the laser dot slides over the surface. Small anomalies such as grain, local unevenness or individual chips are thus “averaged out”, which increases measurement stability. What’s more, imbalances or formal errors are immediately recognisable because they are regularly repeated in the measurement signal.
A practical example shows this very well: A rotating wooden mandrel is to be tested for its diameter. A laser triangulation sensor of the P3 series is used directly on the process. Due to the rotation, the distance value results in a meaningful measurand, from which the diameter is calculated via the geometry.
Two concepts are possible:
Both methods can be used flexibly in production or testing processes – although the individual system is usually more cost-efficient and easier to integrate.
To ensure that measurement tasks also function reliably under real conditions, there are a few points to consider:
Laser triangulation sensors offer a very robust method for thickness and diameter inspections – whether on rotating workpieces or stationary objects. Their high measuring frequency, precision and non-contact operation make them the preferred solution for production and quality control tasks in a wide range of industries.
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