Mitutoyo SJ-301 - Mean Width of the Profile Elements, Sm (JIS, ISO, DIN); Peak Count, Pc (JIS, ISO, DIN); Peak Count, Ppi (JIS, ISO, DIN)

14 - 24 No. 99MBB091A
14.5.14 Mean width of the profile elements, Sm (JIS, ISO, DIN)
A portion projecting upward over the given upper count level is called a profile peak, and a
portion projecting downward below the given lower count level is called a profile valley. The
width of the profile element is the length of the x-segment intersecting with profile peak and
the adjacent profile valley. Sm is the mean of the profile element widths within a sampling
length.
n
i=1
Sm =
1
n
Smi
∑
Count level
Sm1 Smi Smn
Count level
Dead zone
● The following restrictions apply to determining a profile element
• Peaks and valleys must appear alternately.
• The intersection of the assessed profile with the mean line immediately before the profile
element is the start point of itself and is the end point of the previous profile element.
• At the start point of the sampling length, however, if either of the profile peak or profile
valley is missing, the profile element width is not taken into account.
● For ANSI, Sm is defined over the evaluation length.
14.5.15 Peak count, Pc (JIS, ISO, DIN)
The reciprocal of the mean width of the profile elements, Sm, is Pc.
Pc = Unit length/Sm (Unit length = 1 cm)
● For ANSI, Pc is defined over the evaluation length.
14.5.16 Peak count, Ppi (JIS, ISO, DIN)
Ppi is a Pc value that is determined for the unit length of 1 inch.
● For ANSI, Ppi is defined over the evaluation length.