Mitutoyo SJ-210 - Rzjis (JIS2001, Free), Rz (JIS1982, 1994): 10-Point Mean Roughness; Ppi (Free): Peak Count; Δa (ANSI, Free): Slope of the Arithmetic Mean (Angle of the Mean Slope)

No. 99MBB122A
18-30
18.5.16 RzJIS (JIS2001, Free), Rz (JIS1982, 1994): 10-point mean roughness
Rz (JIS) is the sum of the mean height of the 5 highest peaks and the mean depth of 5
deepest valleys, as measured from a line parallel to the mean line.



5
1
5
1
5
1
5
1
ii
YviYpiRz
Rz 10-point mean roughness
 Evaluation profile mountains/peaks and valleys/floors
When the evaluation profile contains a mean line, portions of the profile that project
above the mean line are called “mountains”, and portions of the profile that project
below the mean line are called “valleys”. The highest point of each mountain is called
the “peak”, and the deepest point of each valley is called the “floor”. However, when
the distance of a peak or floor from the mean line is less than 10% of the Ry value, the
peak/floor is not regarded as a peak or a floor.
18.5.17 Ppi (Free): Peak count
Ppi is the value obtained by calculating the number of peaks that occur in 25.4 mm (1 in) of
Pc.
TIP
• The unit for Ppi is displayed as /E (E = 25.4 mm (1 in)).
18.5.18 Δa (ANSI, Free): Slope of the arithmetic mean (angle of the mean slope)
Δa is the arithmetic mean of the absolute values of the local slopes (dz/dx) of the
evaluation profile. The local slope (dz/dx) of the evaluation profile is given by the following
formula:



n
i
dx
dzi
n
a
1
1

321123
945459
60
1




iiiiii
zzzzzz
xdx
dzi
Zi is the height of the i’th point, and Δx is the distance to the adjacent data point.
 For ANSI, RΔa is defined over the entire evaluation length.
Yv1
Y
p
1
Y
p
2
Y
p
3
Y
p
4
Y
p
5
Yv2
Yv3
Yv4
Yv5