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 (sketch above, left). 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 (sketch above, right), 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.
 

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