Length measurement can be done with two displacement sensors or using one displacement sensor in combination with one or more light barriers.

If the object is transported perpendicular to the measurement direction, sensors may be installed on opposite sides. Once calibrated, the system calculates the length from the two distance values and the offset.

If the object moves in measurement direction and comes to a stop, one sensor measures on the front. One or more light barriers detect the opposite end. Length is calculated from the distance to the light barrier and the sensors measurement value.

In case the object runs through the measurement system, the front sensor is placed besides or above the transport system. Again, the opposite end is detected by light barriers.

For calculation of the length, the angle between sensor and front side is taken into account.


Depending on requirements for accuracy, movement and edge profile, width can be measured in different ways.

Besides measurement range, vertical movement has to be taken into account.
For objects with small changes of width, laser micrometers may be used for higest precision.

If the object moves perpendicular to the transport direction, scanning laser triangulation sensors with larger ranges and offsets make sense.

To detect and compensate geometrical errors caused by objects lying in an angle to the transport direction, you can use three sensors on one side.

Example for width measurement of slabs

Width measurement of slabs


Height, like thickness, can be either measured with two sensors, one above and one below the object. 

Second possibility is measurement using a reference plane. As there often is a conveyor under the object to be measured, height measurements typically work with one sensor only.