Sources of uncertainty related to sensor positioning
Displacement sensors

Displacement sensors are usually made up of a part linked to the fixed frame of reference and a part linked to the moving frame of reference (material element for contact sensors, immaterial for non-contact sensors).

The main sources of uncertainty are :

• the positional errors Δx, Δy and Δz of the sensor body relative to the fixed reference frame ;

• the misalignment α of the sensor body and measurement direction ;

• misalignment β of the moving part (misalignment of the measuring axis with respect to the mounting faces of the transducer body for non-contact measuring systems);

• the difference in position γ between the "ideal" contact point and the actual contact point on the target, taking into account the radius of curvature r of the target in the vicinity of the measurement point: r sin γ " (h + Δy) " r γ.

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