This is how repeatability is measured by Agilent's laser system which has 1/10 millon accuracy.
(Agilent is now called Keysight technologies)
As it is shown in the video clip, the variation in the signal points is within 0.5µm.

The differences from proximity sensors

“Proximity sensors” are the most common sensors for detecting workpiece position.

As non-contact type, they can detect an object without damaging or deforming it, however, they are not suited for harsh environment where metal cutting may cause false detection. 

Futhermore, electronic parts inside those sensors are easily affected by external environment (like magnetic field and temperature) , resulting in large signal variation. Mutual interference when used for narrow pitches are also a problem.

On the other hand, Metrol’s “Positioning Switches” are pf precision mechanical type consisting of only mechanical components, which are not affected by external environment such as material, shape, temperature and others.
In addition, Metrol’s switches are free of temperature drifts due to self generation because of no amplifier and other electronic parts.

1. High repetitive accuracy

Metrol High-precision Positioning Switch		Competitor Proximity sensors
Small signal point adjustment variance.		Signal point adjustment variance is large
Possible to determine OK/NG even for detected object with narrow allowable tolerance.		Unable to detect OK/NG objects where allowable tolerance range is small.
Precision mechanical type without any electronic circuitry. Results in no movement differential of signal set position caused by temperature drift from its temperature characteristics.		Signal set points are moved by temperature drift.
Set signal position at limit value of OK range	Can be set to the extreme of limit value ⇒Improvement in both production efficiency and quality management.	Determines NG item as OK item ⇒Decrease in production efficiency (yield rate)
Set signal position at limit value of NG range	Can be set to the extreme of limit value ⇒Improvement in both production efficiency and quality management.	Determines NG item as OK item ⇒Manufacture of defective item.

2. No movement differential

Workpiece seating check using High-precision Positioning Switches No movement differential between set signal position and signal return position makes it possible to detect micro movement of workpiece.

Workpiece seating check using Proximity sensor Micro movement of workpiece cannot be detected as there is a movement differential between the signal set position and signal return position.

Full inspection ensures high repeatability

Repeatability of “High precision type” positioning switches are inspected one by one at our factory before shipping.
Metrol carefully checks over each production process in order to maintain high reliability of our products and to supply them to the world.