17) Surf Text. Uncertainty

Question 1

What is Vertical Displacement Uncertainty?

Answer 1

• Calibrate in the z axis (vertical)
• Type A1 or A2 artefact used to calibrate.
• Accuracy of stylus pickup and transducer - vertical magnification factor of instrument.

Question 2

How do you calculate vertical displacement? Explain the equation parameters.
Z = C*Zm
C = dc/dm

Answer 2

dc = step height
Udc = uncertainity of step height
C = correction factor
Z = Corrected measurement of vertical height
Zm = measured height
dm = measured artefact step height
dc = quoted artefact height

Z = C*Zm
C = dc/dm

Question 3

What are Type “A” standards?

Answer 3

• Used to calibrate vertical component of stylus instruments
• A1 = insensitive to shape or condition of stylus tip (square)
• A2 = insensitive to shape or condition of stylus tip (round)

Question 4

What are the 5 factors that contribute to Zm?

Answer 4

Min of 5 measuremtns taken for dm

Zm depends on: Zm = Zp + Zref + Zn + Zpl + Ztip

Zp = traced profile term (actual height value at any point, doesn’t affect uncertainty analysis)

Zref = Slideway profile term (imperfections in slideway/skid)

Zn = instrument noise (random measurement error of the instrument)

Zpl = plastic deformation term (dependant on stylus, workpiece material, stylus force, shape, local curvature and slopes on surface.

Ztip = effect of tip geometry (required for surface with wavelengths less than radius of stylus tip)